Part One

Survey of the Formations. Analysis of the Fauna.

Stratigraphy. Paleogeography

Chapter I

Lower Devonian of the Anui–Kuyagan Geosynclinal Zone

I. General Characteristics

The most difficult question in the stratigraphy of the Devonian system of the Altai is that of the Lower Devonian—its distribution, facies, and stratigraphic subdivision. This is explained by the fact that the Lower Devonian of the Altai has a very complex composition and is represented by highly diverse facies; in particular, among them an important role is played by deposits with a very distinctive fauna, encountered nowhere else (apart from the Altai). As experience has shown, the stratigraphic subdivision of these deposits is possible only on the basis of a very detailed and comprehensive study of their fauna; partial determinations of only some of its components can lead only to erroneous conclusions about the age and stratigraphic position of the corresponding formations and horizons; this was the case with the Lower Devonian of the Rudny Altai.

By contrast, the Middle and Upper Devonian deposits of the Altai are characterized mainly by a well-studied fauna and are readily paralleled with equivalent deposits of other regions of the Sayan–Altai area and of other countries.

Thus, the central place in the development of the Devonian stratigraphy of the Altai is occupied by the detailed study of its Lower Devonian fauna. This study was carried out by me with respect to the Lower Devonian of the northwestern part of the Altai, where the corresponding deposits are widely developed, are represented by a series of formations, and are characterized by an exceedingly rich fauna. This fauna is very diverse and consists mainly of local forms, among which the genus Leptodontella m. stands out especially; after it I designate this entire fauna as the leptodontellid fauna. The Devonian deposits characterized by this fauna have a fairly constant lithological composition: these are greenish- and yellowish-gray calcareous shales and sandstones with subordinate limestones. As an analysis of the fauna has shown, in facies character they approach the mixed Rhenish–Bohemian type, which in Western Europe is represented, for example, by the graywackes of Erbsloch. The composition of the fauna, however, in the Altai deposits of this type is substantially different, and I believe it will be convenient to call these deposits the Altai type of Eodevonian.

The Lower Devonian deposits of the Altai type have until now hardly been studied. In the literature on the geology of the Rudny Altai they are treated very incompletely and to a considerable extent incorrectly; I gave a brief characterization of them for the northern part of the Gorny Altai in 1935—this characterization must now be substantially expanded, refined, and detailed.

Without any exaggeration it may be said that, without taking into account the Eodevonian of the Altai type, all our summaries on the geology of the Sayano-Altai region are incomplete. Below, the Lower Devonian formations of the Gorny Altai that contain leptodontellid fauna are characterized in detail; their analysis and correlations are based on a detailed study of the most important groups of this fauna: brachiopods, trilobites, and pelecypods. Part II of the present work is devoted to a monographic description of this extensive fauna.

The study of the leptodontellid fauna of the Gorny Altai has brought the composition of the Lower Devonian of this region into an entirely new light.

Instead of fragmentary and schematic indications of the presence of faunistic horizons of the Lower Devonian (see, for example, Nekhoroshev, 1932, pp. 17–19), we can provide a tectono-stratigraphic scheme of the Lower Devonian of the Altai that is fully characterized faunistically. This not only fills a substantial gap in our conceptions of the geology of the Gorny Altai, but also provides a guiding orientation in the analysis of the accumulating materials on the Lower Devonian of Rudny Altai.

The faunistically characterized Lower Devonian deposits in the Altai are confined to two areas: first, they are widely developed in the southwest, within Rudny Altai; the second area of development of the Eodevonian is the northwestern part of the Gorny Altai, the basin of the middle courses of the Anuy and Peschanaya rivers. Here the Lower Devonian is represented by several formations and has an enormous total thickness (7–8 km). Thus, in the northwestern part of the Gorny Altai there is a geosynclinal Devonian zone, which we call the Anuy-Kuyagan zone; the present chapter is devoted to the description of the Lower Devonian deposits of this zone.

Within the Anuy-Kuyagan zone, Lower Devonian deposits are known at a number of localities. In the west they are confined to the Anuy-Ganin graben (Krasnikov, 1935), in which the most ancient formations—the Zhedin and Zigen formations—have been preserved. Farther east, in the Kuyagan district, we find younger, faunistically characterized Eodevonian deposits ($D_1^2$ and $D_1^3$). Detailed field observations and detailed study of the fauna allow me to characterize these formations in sufficient detail, as I have done below. There are, however, in the Anuy-Kuyagan zone a number of localities in which Lower Devonian deposits with fauna have been recorded but were not studied by me; the published materials on them are very schematic and do not allow any definite stratigraphic conclusions to be drawn. These still insufficiently studied Lower Devonian deposits of the Anuy-Kuyagan zone, not divided into formations, are briefly characterized below on the basis of the literature data.

In more southern areas, a faunistically characterized Eodevonian has not been found. V. P. Nekhoroshev (1932, pp. 63–64, 84) was inclined to assign to the Lower Devonian part of the deposits of the Belgebash graben in the central part of the Gorny Altai; on the basis of the study of the fauna of the Belgebash Devonian, I have come to the conclusion that it belongs to the upper parts of $D_2$ and contains no Lower Devonian elements in its composition (see p. 98). In some districts of the Gorny Altai, continental and effusive formations have been established, to which a Lower Devonian age is sometimes attributed; they usually accompany faunistically characterized Middle Devonian deposits and are considered together with the latter in the following chapter.

Thus, the presentation of the materials on the Lower Devonian of the Anuy-Kuyagan zone is made below according to the following plan:

1. Lower Devonian of the Anuy-Ganin graben: Solovikha limestone, Ganin Formation.

1. The Lower Devonian of the Kuyagan district: the Kuyagan, Kondrat’evka, and Medvedevka formations.
2. Undivided Lower Devonian deposits of the northwestern part of the Altai.
3. Stratigraphic scheme of the Lower Devonian of the Anui–Kuyagan zone.

II. The Lower Devonian of the Anui–Ganin Graben

Geological investigations carried out in 1931 by P. F. Krasnikov in the northwestern part of the Altai, in the basin of the middle course of the Anui River, introduced substantial additions to our understanding of the Devonian deposits of the Northern Altai. Along the Ganin Spring, a right tributary of the Anui River, P. F. Krasnikov (1935) discovered faunistically characterized deposits, to which, on the basis of my determinations of the fauna supplied by P. F. Krasnikov, a Lower Devonian age was assigned.

P. F. Krasnikov’s investigations established that, in the northwestern part of the Altai, amid an extensive field occupied by the Lower Silurian green-violet formation, there is, in the form of a broad meridional belt, a graben filled with Upper Silurian and Devonian deposits and named by P. F. Krasnikov the Anui–Ganin belt of the Siluro-Devonian. Within this belt—specifically in its northern part—lie the deposits of the Ganin Formation of the Lower Devonian that I have studied in detail. To P. F. Krasnikov belongs the credit for establishing such major structures as the Anui–Ganin and the situated [[unclear: continuation on next page]].

Legend to Fig. 1

• S₁ (chiefly the green-violet formation)
• Anui–Ganin graben \((S_{2} - D_{1})\)
• Alluvial \(Q\)
• Fauna:
  1 — Solov’yikha horizon \(SD\)
  2 — Rensseleria horizon
  3 — Psevdabgotov horizon
  4 — Paraspirifer horizon \(\} D_{1}\)

Fig. 1. Northern part of the Anui–Ganin graben
(after P. F. Krasnikov)

east of the Kamyshinskaya “belt,” separated the rocks composing them from older ones, and also established a young (apparently Devonian) monzonite intrusion cutting the Lower Devonian. However, P. F. Krasnikov did not subdivide the Silurian–Devonian complex filling the grabens, and the detailed section of the Ganin Formation appended to his report is inaccurate and gives no idea either of the composition or of the bedding of this formation.

The detailed geological investigations of B. F. Speranskii, carried out in 1935, yielded very interesting and important results in refining and detailing the stratigraphy of the Silurian and Devonian deposits of the region. Recently B. F. Speranskii has interpreted his observations in the spirit of active tectonics and has produced very detailed maps of the northern part of the Anui–Ganin and Kamyshinskii grabens. Unfortunately, B. F. Speranskii’s stratigraphic constructions are not always based on a sufficient paleontological foundation, and therefore already now I am compelled to introduce into B. F. Speranskii’s maps certain substantial corrections. Thus, the Solov’yikha limestones (developed north of the village of Solov’yikha, Fig. 1) on B. F. Speranskii’s map are assigned to the Eifelian stage, whereas study of their fauna has shown that they are of Gedinnian age, i.e., they constitute a horizon that must be regarded as transitional between \(S_2\) and \(D_1\). To the Upper Silurian (the Chagyr limestone) on B. F. Speranskii’s map there is assigned, apparently, the Rensselaeria horizon of the Ganin Formation (see below), which crops out along the right side of Ganin Creek, west of the settlement of Kireevskii (Fig. 2).

In 1932 I had the opportunity to make a traverse along Ganin Creek; the observations made on the traverse and the subsequent detailed study of the fauna allowed me, within the Ganin Formation, in addition to the Rensselaeria, to distinguish two more faunistic horizons—the pseudotogatous and the Paramnigenia horizons. Thus, I can indicate the following faunistic horizons of the Lower Devonian of the northern part of the Anui–Ganin graben:

\[ \begin{array}{l} \text{Paramnigenia horizon} \\ \text{Pseudotogatous horizon} \\ \text{Rensselaeria horizon} \end{array} \left\} \ \text{Ganin Formation}^{1)} \right. \]

Break

Solov’yikha limestone

The names of the horizons (except for the Solov’yikha) are given according to characteristic fossils:

Paramnigenia — the genus Paramnigenia Khalf.
pseudotogatous — the species Eospirifer pseudotogatus Khalf.
Rensselaeria — the genus Rensselaeria Hall.

Below is given a detailed, chiefly paleontological, characterization of these deposits.

A. Solov’yikha limestone

The limestones situated north of the village of Solov’yikha I did not have occasion to study under field conditions. I also have no information on observations by other authors concerning the conditions of occurrence of these limestones, and therefore am unable to characterize the volume and composition of the formation into which they enter. The fauna that I have processed and on the basis of which I determine the age of the Solov’yikha—

\(^{1)}\) The composition of the Ganin Formation is not exhausted by these three horizons (see p. 27).

limestones as Gedinnian comes from the collections of M. P. Nagorskii; these collections were of a chance character and were not accompanied by mapping of the corresponding area, and therefore the question remains open as to whether all the limestones designated on B. F. Speranskii’s map as Eifelian are of Gedinnian age, or whether here we have deposits of different ages, including Eifelian ones (p. 79). It is obvious that this question must be resolved by additional field observations and by the processing of additional collections of fauna.

But even without these additional collections, the fauna found by M. P. Nagorskii provides us with very important information: it has made it possible to establish in the Altai a horizon corresponding to a certain transitional moment between \(S_2\) and \(D_1\), i.e., to the Gedinnian stage in its exact sense. As is known, up to the present time the literature has maintained the opinion asserting that in the Altai the Devonian begins only with the Koblenzian stage and that between \(S_2\) and \(D_1\), within the Altai, there was a long hiatus. Now we know that in the Altai there is a complete section of the Eodevonian, and that its lowermost member, already lying on the boundary with the Upper Silurian, is our Solov’ikha limestone. This conclusion is based entirely on the analysis of the fauna, to the detailed consideration of which we now turn.

The dense, in places silicified limestone of which the fossil-bearing hand specimens supplied to me by M. P. Nagorskii consisted proved almost impossible to prepare in the raw state; when pieces of this limestone were split, the organic remains enclosed in it were, as a rule, destroyed. However, after moderate calcination and rapid cooling, a numerous fauna was extracted from these hand specimens, in part very well preserved. Even the most cursory inspection of this fauna makes it possible to note three of its conspicuous features.

1. The small size of the components of this fauna: specimens 1 cm in size make up a very insignificant part of all the samples; larger ones are absent (with the exception of a single solitary coral).

2. The diversity of composition in relation to the total number of prepared samples: only two forms (Uncinulus paranucleolatus n. sp., Atrypa comata Barr.) are each represented by several specimens; in the overwhelming majority of cases each specimen belongs to a separate species, and even species represented by two specimens are very few.

3. The decisive predominance of brachiopods in the composition of this fauna: among the several dozen specimens making up our collection, there is only one representative each of tetracorals, gastropods, cephalopods, and trilobites; all the remaining samples are brachiopods.

The processing of this collection showed that new forms predominate in the composition of the given fauna. At the same time the alien character of many forms is expressed so distinctly that it can be established with complete obviousness even on incomplete single specimens. Having limited material at my disposal and wishing to give the reader as complete an idea as possible of this fauna, which is very important for the stratigraphy of the Altai, I considered it necessary (at the risk of provoking certain reproaches) to describe under new species names some of those specimens which, although incomplete, nevertheless make it possible to formulate clearly the distinctive diagnostic characters of a new species. Considerable difficulties in the processing of this fauna were encountered in establishing the generic affiliation of our new species: in a number of cases, when the assignment of a given specimen to a new species no longer raised doubts, referring it to one or another genus with complete certainty proved impossible: with only one specimen available, investigation of the internal structure (on which the modern classification of brachiopods is based)

it is impossible without sacrificing this monotype. In this case I preferred to accompany the generic determination with a question mark and leave it to subsequent studies to introduce a clarification, rather than destroy the holotype of the species I am establishing; all the more so because such a sacrifice does not always yield a positive result in the sense of clarifying the generic determination, as I became convinced from bitter experience when attempting, by grinding down the apices, to establish the generic affiliation of the only specimen of Leiorhynchus (?) subcordatus n. sp.: the interior of the shell proved to be filled with coarse-crystalline calcite, and I found no elements of the internal skeleton. The foregoing explains why, among the 27 species of brachiopods of the Solov’yikha fauna, one third (nine species) have a question mark after the generic name; 8 of these 9 species are new.

The general list of forms of the Solov’yikha fauna available to me is as follows:

No.	Form	Number of specimens
1	Cyathophyllum sp.	1
2	Sieberella acuticostata n. sp.	1
3	Gypidula n. sp. ex gr. G. optata (Barr.)	1
4	Gypidula caduca (Barr.) var. bicostata n. nom.	1
5	Clorinda (?) simulans n. sp.	1
6	Clorinda (?) sulcata n. sp.	1
7	Corrugatella cf. stephani (Barr.)	1
8	Camarotoechia dichotoma n. sp.	1
9	Camarotoechia pulchella n. sp.	1
10	Camarotoechia jejuna (Barr.) var. geniculata n. nom.	1
11	Uncinulus paranucleolatus n. sp.	9
12	Leiorhynchus (?) subcordatus n. sp.	1
13	Leiorhynchus (?) paradoxus n. sp.	1
14	Atrypa (?) umbra (Barrande)	3
15	Atrypa comata Barrande	6
16	Atrypa quasi-comata n. sp.	2
17	Atrypa supramarginalis n. sp.	3
18	Atrypa insolita Barrande	1
19	Atrypa transversa n. sp.	1
20	Atrypa nagorskii n. sp.	1
21	Septatrypa (?) altaica Sennikov	2
22	Spirifer jaschei (Roem.) Kays.	2
23	Delthyris latisinuata n. sp.	1
24	Martinia (?) rhomboidalis n. sp.	2
25	Rhynchospirina formosa (Hall)	2
26	Rensselaeria globosa n. sp.	1
27	Cryptonella (?) trigonalis n. sp.	1
28	Cryptonella (?) sp.	1
29	Strophostylus nanus n. sp.	1
30	Orthoceras sp.	1
31	Bronteus sp.	1

Let us proceed to an age analysis of this fauna; excluding for the time being from consideration four forms determined only to genus (Cyathophyllum sp., Cryptonella sp., Orthoceras sp., and Bronteus sp.), we shall have a list of 27 forms, among which 9 forms, constituting 33%, are known from other areas or other horizons. For the Lower Devonian faunas of the northern Altai, such a percentage of forms that could be identified with previously known ones must be considered high and, consequently, favorable—

unfavorable for determining the age of the fauna; the 9 forms mentioned above are as follows:

1. Gypidula caduca (Barr.) var. bicostata n. nom.
2. Corrugatella cf. stephani (Barr.)
3. Camarotoechia jejuna (Barr.) var. geniculata n. nom.
4. Atrypa(?) umbra (Barr.)
5. Atrypa comata (Barr.)
6. Atrypa supramarginalis n. sp.
7. Atrypa insolita Barr.
8. Spirifer jaschei (Roem.) Kays.
9. Rhynchospirina formosa (Hall).

Gypidula caduca var. bicostata is cited by Barrand from the Upper Silurian limestone of Kolednik, Czechoslovakia.

Corrugatella stephani is a form that has a universal distribution in the Bohemian fauna of the Lower Devonian. As noted in the description of this species (Part II), it is represented in our fauna by a single small specimen, indistinguishable from juvenile “Strophomena” stephani; the notation “cf.” in the name of this specimen is prompted by the following considerations: the fauna of the Solov’yikha limestone has a clearly dwarfed character, and in it small dimensions are not infrequently also characteristic of adult individuals. Even if the given specimen represents not a juvenile but an adult stage, its differences from adult representatives of Corrugatella stephani do not permit it to be assigned to this species. However, I am inclined to regard our specimen as a juvenile individual, for the following reasons: the fauna of the Rensseler horizon likewise has a dwarfed character (see below), and from its example we can convince ourselves that it is precisely the strophomenids, to a lesser degree than other brachiopods, that undergo dwarfing in this case and, in the adult state, attain considerable size. If, however, the specimen under discussion is, as we assume, juvenile, its identification with Corrugatella stephani is necessary, i.e., it will testify in favor of the Lower Devonian, within which this species has a broad vertical distribution: O. I. Nikiforova (1937, p. 31) cites from the Monakovo beds (transitional from S to D) of Central Asia a form designated Stropheodonta cf. stephani; D. Le Maître (1934, p. 49) established the presence of this species in the limestones of Chaudefonds of the Armorican Massif, which have a transitional age from D₁ to D₂. Between these two extreme positions Corrugatella stephani is distributed in various horizons of the Eodevonian (Czechoslovakia, the Carnic Alps, the Urals, Rudny Altai, Kuzbass).

Camarotoechia jejuna var. geniculata has been encountered in Czechoslovakia in the Lower Devonian Koněprusy limestone.

Atrypa umbra is a widely distributed Upper Silurian form, with very close analogues in the Lower Devonian of Europe (Atrypa sublepida) and North America (Anoplotheca concava); our specimens of Atrypa umbra are indistinguishable from representatives of this species from the upper horizons of S₂ of Central Asia and the Urals.

Atrypa comata is widely distributed in the Lower Devonian of Europe; according to A. N. Khodalevich (1937, p. 66), in the Urals this species appears in S₂, passes through D₁, and extends into the lower parts of D₂. Such a broad vertical distribution of Atrypa comata in the Urals seems to me doubtful and in need of verification. Our specimens of this species are in no way distinguishable from its representatives from D₁ of Czechoslovakia.

Atrypa supramarginalis has been encountered in the overlying Rensseler horizon of the Ganinskaya Formation (D¹₁).

Atrypa insolita is widespread in the Upper Silurian of Czechoslovakia and the Urals. This species in \(D_1^{1}\) is also present in the Carnic Alps, in association with three species of the genus Karpinskya Tschern. and spirifers of the Lower Devonian. There are likewise indications of the presence of this species in the Lower Devonian of Czechoslovakia.

Spirifer jaschei—a Lower Devonian species, widespread in Germany, northern France, and, apparently, in the Urals.

Rhynchospirina formosa—is widespread in the uppermost horizons of the Silurian and in the lower half of the Eodevonian of North America; it has also been encountered in the Lower Devonian of Central Asia (Pamir).

Putting into a table the stratigraphic indications considered for nine of our forms, we obtain:

Table 1

Names of forms	\(S_2\)	\(D_1\)
Gypidula caduca var. bicostata	+	−
Corrugatella cf. stephani	+ (rare¹)	+
Camarotoechia jejuna geniculata	−	+
Atrypa (?) umbra	+	−
Atrypa comata	−(?)	+
Atrypa supramarginalis	−	+
Atrypa insolita	+	+ (rare)
Spirifer jaschei	−	+
Rhynchospirina formosa	+	+
	5	7

From this table² it is evident that in the fauna of the Solov’ikhino limestone there are:

1) two forms characteristic only of the Silurian, among them such an important index form as Atrypa umbra;

2) three forms passing from the Silurian into the Devonian;

3) four forms characteristic only of the Devonian, among them Spirifer jaschei—one of the earliest representatives of the Devonian fauna in European deposits, widespread already in the very lowest horizons of the Eodevonian.

In its mixed Silurian–Devonian character, the fauna of the Solov’ikhino limestone is similar to the fauna of the Gedinnian deposits of the Ardennes and Artois or to the fauna of the Keyser limestone of the state of Maryland. Thus, on the basis of the stratigraphic indications of the fauna set out above, the age of the Solov’ikhino limestone should be determined as Gedinnian.

We turn to determining the geographic type of our fauna, i.e., to considering the character of the fauna of the Solov’ikhino limestone from the standpoint of its connection with American and European faunas; this should lead us to certain conclusions about the connection of the Gedinnian basin of Northern Altai with the seas of America and Europe. In doing so, we shall rely not only on those forms that could be identified with previously established species, but also on a number of new species that show a definite similarity to one or another of the previously described forms. Thus, for example, our Septatrypa (?) altaica Senn. shows a comp—

¹ The Monak beds of Central Asia, occupying a transitional position between \(S\) and \(D\).

² In the present work, tables in the text are numbered with Arabic numerals, and plates with photographic illustrations with Roman numerals.

an entirely obvious affiliation with the group of atrypids, which is so characteristic of the Bohemian–Uralian Hercynian. With respect to such forms, we generally allow that their similarity has the character of a systematic vicariate, i.e., they are genetically close and may serve to establish a connection between the faunas being compared.

Both here and everywhere below we shall divide the forms analyzed into the following geographical groups:

a) forms with a sharply expressed endemic character, having no close analogues in other faunas—the En group;

b) forms of European type (identical and vicariant)—the Eu group;

c) forms of American type (identical and vicariant)—the Am group;

d) forms of Asiatic type in the broad sense—the As group;

e) forms having vicariant analogues in the European and American faunas, i.e., forms of a to some extent cosmopolitan type—the Co group.

In our fauna we find representatives of the groups Eu, Am, En, and Co.

En—specifically local forms:

1. Sieberella acuticostata
2. Clorinda (?) simulans
3. Clorinda (?) sulcata
4. Camarotoechia pulchella
5. Leiorhynchus (?) subcordatus
6. Leiorhynchus (?) paradoxus
7. Atrypa supramarginalis
8. Atrypa transversa
9. Atrypa nagorskii
10. Martinia (?) rhomboidalis
11. Rensselaeria globosa

Eu—forms of European type:

1. Gypidula n. sp. ex gr. G. optata (Barr.)
2. Gypidula caduca (Barr.) var. bicostata n. var.
3. Camarotoechia jejuna (Barr.) var. geniculata n. nom.
4. Corrugatella cf. stephani (Barr.)
5. Atrypa (?) umbra (Barr.)
6. Atrypa comata Barr.
7. Atrypa quasicomata n. sp.
8. Atrypa insolita Barr.
9. Septatrypa (?) altaica Senn.
10. Spirifer jaschei (Roem.) Kays.
11. Delthyris latisinuata n. sp.
12. Cryptonella (?) trigonalis n. sp.

Am—forms of American type:

1. Uncinulus paranucleolatus n. sp.
2. Rhynchospirina formosa (Hall)

Co—forms of cosmopolitan type:

1. Camarotoechia dichotoma n. sp.
2. Strophostylus nanus n. sp.

This distribution of species by groups may be presented in the form of the following table:

Table 2

Geographic groups	Identical	Vicariant	Total
of the European type—Eu	7	5	12 (44%)
of the American type—Am	1	1	2 (7.5%)
of the endemic type—En	—	—	11 (41%)
of the cosmopolitan type—Co	—	2	2 (7.5%)

The figures given above show that the most important feature of the fauna of the Solovikha limestone is the sharp quantitative predominance in it of endemic forms and forms of the European type. Concerning the latter, the following must additionally be said: all of them quite clearly belong to the Bohemian–Uralian (Hercynian) type of Lower Devonian fauna. The influence of the American fauna proves to be very weak, but it cannot fail to be noted that in our fauna there is nevertheless such a typical North American form as Rhynchospirina formosa: its representatives in the fauna of the Solovikha horizon show complete identity with the North American ones.

From these data we are entitled to conclude that the Gedinnian basin of the Northern Altai had very limited (probably circular¹) communication with the seas of North America, from which individual immigrants penetrated into it. Communication with the European and Ural–Turkestan sea, however, was broad and open; the abundance in our fauna of endemic forms does not contradict this: taking into account the enormous distances that separated the North Altai Gedinnian basin from the Ural–Turkestan basin, one need not be surprised at the presence in it of specific forms. Thus, the fauna of the Solovikha limestone is a fauna of the Bohemian–Uralian (Hercynian) type, with a small admixture of North American forms and with a large number of endemic elements.

One addition must be made to this characterization: our fauna differs from the other Gedinnian faunas of the Hercynian type in one circumstance—its stunted character. Neither in Bohemia and the Carnic Alps, nor in the Urals and Central Asia do we encounter Gedinnian faunas whose constituents would be distinguished by such small dimensions as the representatives of the fauna of the Solovikha limestone. Since all specimens of the Solovikha fauna possess abnormally small dimensions, this circumstance cannot be explained by accidents of collecting: it is altogether improbable that all these specimens should have turned out to be juvenile individuals, and that not a single adult specimen was found. In addition to this consideration of a general character, we can prove that small size is a natural property of the components of the Solovikha fauna by analyzing their morphology. For this purpose let us consider representatives of two different types—brachiopods (Rhynchospirina formosa) and mollusks (Strophostylus nanus).

In the degree of convexity of the valves, the curvature of the ventral beak, and the development of the sinuses, our specimens of Rhynchospirina formosa correspond to the adult stage of representatives of this species and cannot be regarded as juvenile individuals; nevertheless, they are two to three times smaller than ordinary American specimens of Rhynchospirina formosa.

The same may be said with regard to Strophostylus nanus: in the relative dimensions of the first and second (last) whorls of the shell, and in the degree of inflation of the last whorl, our specimen must be regarded as an adult individual. It is true that species close to Strophostylus nanus possess one additional whorl (in the adult stage), but even if one admits that our specimen could, during life, have added this third whorl with a proportional increase of the shell—even in that case its dimensions would have been several times smaller than the dimensions of the shells of related American and European forms.

At present it is not possible to indicate the causes of such a depressed condition of our fauna: for this it would be necessary to subject the Zhedinian deposits of the Gorny Altai to comprehensive study over a considerable area, whereas at present they are known to us (and incompletely at that) only at a single locality. We must therefore confine ourselves to noting the fact that the conditions of existence in the Zhedinian basin of the Northern Altai were unfavorable and had a depressing effect upon its inhabitants.

As has already been indicated, the depressed character serves to distinguish the Solovykhino fauna from the Zhedinian faunas of Eurasia that are close to it. The most similar to it in this respect is the depressed fauna recently described by D. M. Grubbs (1939), derived from concretions in the Niagaran deposits of the Chicago region: in this fauna, as in the Solovykhino fauna, specimens possessing the features of mature individuals differ from representatives of the very same species from the synchronous dolomites of Racine by dimensions two and three times smaller.

B. The Ganino Formation

1. Characterization of the Formation

A brief characterization of the deposits of the Ganino Formation was given by P. F. Krasnikov (1935, p. 17); from this characterization it follows that the deposits of the Ganino Formation are represented chiefly by greenish-gray and brownish-gray marly sandstones and subordinate shales and gray limestones. In the same year I briefly characterized the fauna of the Ganino Formation (Khalfin, 1935, pp. 29–30, 33); only a few forms from the pseudotogatov horizon were preliminarily identified, namely:

Strophonella planuscula,
Schuchertella altaica,
Spirifer subsinuatus,
Atrypa reticularis.

From comparison with the more thoroughly studied faunas of other Lower Devonian formations of the Altai, I assigned the Ganino Formation (calling it the “Ganino Spring succession”) a Lower Devonian age. Recently B. F. Speransky and I, independently of one another, have used the term “Ganino Formation” for these deposits; I have given a brief characterization of its three constituent horizons—the Rensselaeria, pseudotogatov, and Paramnigene horizons (Khalfin, 1940a, p. 28); the spiriferids of the pseudotogatov horizon have been described in detail in a special article (Khalfin, 1944).

In its lithological composition and fauna, the Ganino Formation belongs to the Altaian type of the Lower Devonian, being its most ancient member, corresponding to the Zigenian stage ($D^1_1$); in it there appears for the first time the leptodontelloid fauna characteristic of the Altaian Lower Devonian.

On the basis of observations made by me in 1932 during a traverse along Ganin ravine, I can give the following description of the section of the Ganin Formation. Ganin ravine, in its upper part (near the settlement of Kireevskii and above), runs almost across the strike of the Ganin Formation; the right side of its valley provides a good section of its deposits. The ravine mentioned in its upper part flows from east to west; the rocks of the Ganin Formation have a north-northeasterly strike; the formation as a whole dips steeply to the southeast. We shall begin the description of the section from its western part, which is the lowest stratigraphically (Fig. 2).

The lower (stratigraphic) part of the Ganin Formation is represented by a limestone horizon, approximately 125 m thick, which is exposed somewhat west of the settlement of Kireevskii. Eastward (higher stratigraphically) from this horizon, for a distance of more than a kilometer, exposures of the pseudotogatovyi horizon extend; they form a kilometer-thick homoclinal sequence composed of yellowish- and greenish-gray platy sandstones, with dip angles from 70° to 90°. In the lower half these sandstones contain a large number of thin limestone interbeds, occasionally with corals; in the upper part lie four (see Fig. 2) brachiopod faunistic beds, the study of whose fauna (see below) showed that in this case there is no repetition of beds and that the sequence of the pseudotogatovyi horizon is homoclinal.

Legend:

• Rensseleria horizon
• Pseudotogatovyi horizon
• Poramnitel′ horizon
• Faunistic beds of the pseudotogatovyi horizon
• \(S_1\)
• Monzonite-porphyries

Fig. 2. Section of the Ganin Formation along the right side of Ganin ravine east of the settlement of Kireevskii

Farther to the east lies a body of monzonite-porphyry, which divides the section of the Ganin Formation into two parts: the western (footwall) part characterized above, and the part situated east of this intrusive body (hanging wall). The monzonite-porphyry body forms a series of apophyses that intrude concordantly into the Ganin Formation and lie in agreement with its beds. The first of these, about 20 m thick, is situated opposite the eastern end of the Kireevskii settlement; it and the two more massive following ones lie among the deposits of the pseudotogat horizon, interbedding with the faunistic beds of the latter (Fig. 2). East of faunistic bed IV begins the continuous development of intrusive porphyries over a distance of one and a half kilometers; only in one place, in the western part of this field, has a fragment of marly rocks of the Ganin Formation been preserved. On the eastern side of the intrusive body there is observed the same alternation as on the western side, of its small apophyses and marly rocks, completely analogous to the rocks of the pseudotogat horizon. A description of the rocks of this intrusion is given by G. F. Krasnikov (1935, pp. 24–26), to whose work the interested reader may turn.

Above (along the course of Ganin Creek) the monzonite-porphyry body lies the eastern part of the section of the Ganin Formation; the intrusive body occupies the middle part of this section, making it difficult to compare and correlate the western and eastern parts of the formation. This eastern part of the section may be briefly characterized as follows: it is composed of rocks lithologically quite analogous to the rocks of the pseudotogat horizon, i.e., greenish and yellowish-gray marly sandstones, which on weathering become brown. But, in contrast to the western part of the section, where the deposits of the rensseleriid and pseudotogat horizons lie entirely monoclinally, in the eastern part there is development of small folds with amplitudes of 100–300 m, in places apparently complicated by small disjunctive structures. Thus, immediately beyond the field of development of the monzonite-porphyries, where the course of Ganin Creek turns from northwestern to latitudinal, the closure of a small anticline is excellently exposed, very effectively outlined in the field by outcrops of limestone participating in the structure of this fold.

Farther to the southeast, changes in the dip of the marly rocks mark yet another similar anticlinal fold; finally, the last of these is followed, complicated by a small disjunctive, by a syncline, and beyond it intrusive porphyries again acquire continuous development.

Thus, in the upper course of Ganin Creek, between two fields of development of intrusive rocks, we observe, over a distance of one and a half kilometers, the eastern part of the Ganin Formation; over the indicated distance I counted three synclinal and two anticlinal folds (see Fig. 2). Fauna was found by me in the limestone mentioned above (corals) and in the very outermost (to the southeast) syncline, which is composed of the Parafimien horizon with a characteristic lagoonal fauna; the thickness of this horizon is 125–150 m.

We turn to the question of correlating the eastern and western parts of the section of the Ganin Formation; in considering this question we shall take into account the following points from the materials set forth above:

a) the lithological composition, in general features, and the strike of the rocks are the same for the western and eastern parts;

b) the western part represents a homoclinal bed sequence, steeply dipping eastward, one kilometer thick, and therefore cannot fit into the small folds of the eastern part, whose amplitude does not exceed three hundred meters;

c) the faunistic beds in the western and eastern parts are different;

c) the extreme western member of the section is the Rensselaerian horizon, marking the initial stage of the transgressive Ganin Formation, which lies upon S;

d) the extreme eastern member of the section is the Paramonigenian horizon, represented by lagoonal deposits and, consequently, marking the final stage in the formation of a certain formation, usually preceding a break in sedimentation.

A comparison of all these data leads me to the conclusion that the western and eastern parts of the section under analysis represent the lower and upper parts of a single (Ganin) formation, the middle part of which is occupied by the body of monzonite-porphyry; this entire formation is a homoclinal sequence, the upper (eastern) part of which is complicated by small folds and, in part, by small disjunctives. In attempting to determine the total thickness of the Ganin Formation in this section we encounter great difficulties caused by the presence, within this formation, of the monzonite-porphyry intrusion. Since it would be entirely inappropriate here to enter into consideration of the complex “problem of the space” of plutonogenesis, we cannot overcome the difficulties indicated above, but can only circumvent them by establishing the extreme limits of the possible thickness of the formation described. Depending on whether we assume that the space occupied by the intrusion arose entirely through the absorption by the magma of part of the rocks of the Ganin Formation (Fig. 3), or that the magma penetrated along the contact between the beds of this formation, with their simple pushing apart,

Fig. 3. Schematic section of the Ganin Formation: 1—the Rensselaerian horizon; 2—the pseudotogatov horizon; 3—the Paramonigenian horizon; the bodies of monzonite-porphyry are shaded.

we obtain, for the thickness sought, extreme limits of 3 km and 2 km; the upper of these is obtained taking into account a certain “assimilated” horizon with a thickness of up to 900–1000 m.

In any case, the thickness of the Ganin Formation is very considerable, but is not exceptional or unusual for the Lower Devonian formations of Altai: the Medvedev Formation, for example, has a thickness of the same order (see p. 62). It should also not be overlooked that the Ganin Formation is composed chiefly of comparatively coarse clastic material (sandstones); for such sequences, the thickness established above, within the limits of 3 km, is not phenomenal.

The lower third of the Ganin Formation is encompassed by two faunistic horizons—the Rensselaerian and the pseudotogatov; the uppermost member of the formation is the Paramonigenian horizon. A detailed faunistic characterization of these horizons is given below. Here it is necessary to note that they do not encompass the entire formation: we can say nothing, from the Ganin section, about its middle part, if we allow for the possibility of the presence of an “assimilated” horizon; obviously, in this case the possibility is not excluded that in the middle part of the formation there were also faunistic horizons and that, in time, they may be found in other places. In the upper part of the formation there is (as noted above) a horizon of coral limestones, the fauna of which remained unstudied; finally, between this limestone and the Paramonigenian horizon

a rather considerable part of the formation is enclosed in which no fauna has been found by me and which for the time being I call the “barren horizon.” Thus, in its final form, the composition of the Ganin Formation, since it can be clarified on the basis of study of the Ganin section, will be as follows (from top to bottom):

Horizon	Thickness
Paramnigenia horizon	about 150 m
Barren horizon	700 m
Coral horizon	100 m
Assimilated horizon	900 m
Pseudotogatov horizon	1000 m
Rensselaeria horizon	125 m
Total	3000 m

For determining the stratigraphic position of the formation, for age and facies correlations, and for paleogeographic reconstructions, the horizons containing organic remains are naturally of greatest importance: the Rensselaeria, Pseudotogatov, and Paramnigenia horizons, to whose faunal characterization we now turn.

The standard of the Ganin Formation is the section described above along the Ganin spring, a right tributary of the Anui River.

2. Rensselaeria Horizon

Two hundred meters west of the western end of the settlement of Kireevskii, on the right side of the valley of Ganin spring, light-gray and gray massive limestones, not infrequently of lumpy structure, are exposed; in part they are coral limestones, and in places they contain abundant crinoid columnals and stems. The outcrops of these limestones extend for about one and a half hundred meters across their strike. These limestones constitute the lower member of the Ganin Formation—the Rensselaeria horizon. Upward they are replaced by greenish-gray marly rocks interbedded with limestones. Investigations by B. F. Speranskii (1941), who mapped this area in detail, established that the limestones of the Rensselaeria horizon (B. F. Speranskii considered them Chagyr Upper Silurian) lie transgressively upon the Lower Silurian variegated-color formation. Thus, the Ganin Formation illustrates and confirms M. A. Usov’s statement that: “the occurrence of limestones at the base of a transgressive formation was frequently observed in the study of the Paleozoic deposits of the West Siberian Territory” (Usov, 1936, p. 31).

The Rensselaeria horizon is conformably overlain by the Pseudotogatov horizon.

The fauna of the Rensselaeria horizon is abundant and diverse; within it the decisive predominance belongs to two groups—Tabulata and Brachiopoda; in addition, certain gastropods, namely Capulidae, are significantly developed, in the usual association with crinoids (stems and columnals), as well as ostracods. As a sparsely distributed group, pelecypods should be noted, and finally, as exceedingly rare single specimens, solitary tetracorals and trilobites occur. Of this considerable fauna, the coelenterates and ostracods have remained unstudied. The complete absence of bryozoans and cephalopod mollusks in this fauna deserves attention.

Among the features of this fauna that may be noted before consideration of its individual components is the depressed character of most of its representatives; in this respect it reveals—

…reveals a known similarity to the fauna of the Solov’yikha limestone. A characteristic feature of our fauna is the abundance in it of representatives of the genus Rensselaeria Hall: they form an autochthonous group consisting of 9 species, which amounts to almost half of all identified brachiopods of this fauna. In the Rensselaeria horizon, Leptaena bouei Barrande appears for the first time—one of the most important forms of the Altai Lower Devonian, passing through all its formations and usually abundantly represented in all formations of \(D_1\) Altai.

Among the widespread forms, in addition to the rensselaeriids, are the species:

Spirifer geyeri Scup.
Atrypa supramarginalis n. sp.
Camarotoechia cf. princeps (Barr.)
Cyrtina heteroclita (Defr.)
Stropheodonta patersoni Hall var. praecedens Cl.

These forms, as well as some species of rensselaeriids, are represented in our collection by 4 to 8 specimens each. Alongside them, almost half—13 forms—are represented by single specimens; this applies especially to mollusks, although capulids apparently are also sufficiently abundant in the fauna of the Rensselaeria horizon.

Not counting forms identified approximately (7), of the remaining (21) it was possible to identify 6 species with previously established ones:

Spirifer geyeri Scup.
Cyrtina heteroclita (Defr.)
Leptaena bouei (Barr.)
Stropheodonta patersoni Hall var. praecedens Clarke
Orthonychia acuta (A. Roem).
Nuculoidea lodanensis (Beush).

This amounts to 28.5%; the remaining 71.5% are new forms, chiefly representatives of the genus Rensselaeria.

The general list of the forms identified by me in this fauna and described in Part II is as follows:

No.	Form	Number of specimens
1	Levenea sp.	1
2	Stropheodonta patersoni Hall var. praecedens Cl	4
3	Leptaena bouei (Barr.)	2
4	Camarotoechia cf. princeps (Barr.)	5
5	Camarotoechia sp.	1
6	Rhynchotretina aequivalvis n. gen. et n. sp.	3
7	Atrypa supramarginalis n. sp.	8
8	Spirifer geyeri Scupin	8
9	Cyrtina heteroclita (Defr.)	4
10	Cyrtina pygmaea n. sp.	1
11	Rhynchospirina simulans n. sp.	1
12	Rensselaeria navicelliformis n. sp.	2
13	Rensselaeria minuta n. sp.	2
14	Rensselaeria pygmaea n. sp.	4
15	Rensselaeria gibbosa n. sp.	6
16	Rensselaeria n. sp.	1
17	Rensselaeria glabra n. sp.	3

1. Rensselaeria altaica n. sp. . . . . . . . . . . . . . . . . . . 7
2. ” paragibbosa n. sp. . . . . . . . . . . . . . . . . . . . . . . 6
3. ” nana n. sp. . . . . . . . . . . . . . . . . . . . . . . . . . . 2
4. Orthonychia acuta (A. Roem.) . . . . . . . . . . . . . . . . . 1
5. Platyceras altaicum n. sp. . . . . . . . . . . . . . . . . . . . 1
6. ” vulgare n. sp. . . . . . . . . . . . . . . . . . . . . . . . . 1
7. ” nodoso-costatum n. sp. . . . . . . . . . . . . . . . . . . . 1
8. Nuculoidea lodanensis (Beush.) var. altaica? . . . . . . . 1
9. Cypricardinia cf. gratiosa Barr. . . . . . . . . . . . . . . 1
10. Actinopteria sp. . . . . . . . . . . . . . . . . . . . . . . . . 1
11. Proetus sp. . . . . . . . . . . . . . . . . . . . . . . . . . . 1

To determine the age of the fauna we shall, of course, first of all make use of the forms that could be identified with previously described species: of six such forms, only Cyrtina heteroclita has a wide vertical range and cannot be useful to us. On the other hand, for our purposes some forms identified approximately, or new ones, may to a certain extent be used, namely: Levenea sp., the genus Rensselaeria as a whole, Atrypa supramarginalis n. sp., Cypricardinia cf. gratiosa Barr.

Levenea sp. by itself cannot serve as an exact indicator of age (the genus Levenea is distributed in \(S_2—D_2\)), especially since in our fauna it is represented by a single incomplete specimen; but this specimen is interesting in that it shows the closest resemblance to representatives of the genus Levenea from the lower part of the pseudotogate horizon, which have a clearly expressed Lower Devonian type.

Stropheodonta patersoni praecedens was described by J. M. Clark from the Lower Devonian limestone of Gaspé, Quebec Province, Canada; this form belongs to those elements of the Gaspé limestone fauna that have an Oriskanian \((D^2_1)\) aspect, but already existed in Helderbergian \((D^1_1)\) time in the Gaspé basin.

Leptaena bouei is the most important guide form of the European and Altai Lower Devonian; already in the pseudotogate horizon it occurs in mass development.

Atrypa supramarginalis, possessing a general resemblance to the Silurian Atrypa marginalis, links our fauna with the Emsian fauna of the Solovikha limestone, where this species is also encountered. The Solovikha representatives of this species differ in a very insignificant detail in the morphology of the shell: in them the saddle and sinus are broader and flatter than in Atrypa supramarginalis from the Rensselaeria horizon. Of course, these differences are insufficient to separate them into a distinct species, but, taking into account the occurrence of the compared specimens in deposits of different age, they may be regarded as Waagenian mutations, namely:

Atrypa supramarginalis mut. \(\alpha\)—Solovikha horizon, \(SD_1\).
Atrypa supramarginalis mut. \(\beta\)—Rensselaeria horizon, \(D^1_1\).

Spirifer geyeri is a typical Lower Devonian form: it is distributed in the Lower Devonian of the Carnic Alps and the eastern slope of the Urals; the significance of this species for establishing the age of our fauna is all the greater because it is the most widespread form in this fauna.

Nuculoidea lodanensis is a Coblenzian form of Western Europe; in the Kondrat’evo Formation \((D^2_1)\) of the Altai a local variety, altaica, has been found, to which the specimen from the Rensselaeria horizon possibly also belongs.

Cypricardinia cf. gratiosa also serves as an indication of a Lower Devonian age (Cypricardinia gratiosa is widespread in the Siegenian deposits of Czechoslovakia).

Orthonychia acuta is distributed in all stages of the Eodevonian of Western Europe (Bohemia, the Harz, the Rhenish Slate Mountains, Brittany).

Finally, the rensselaeriids are in general a Devonian group of brachiopods (essentially Lower Devonian); in the Upper Silurian only very rare representatives of this group appear; and although the endemic composition of our rensselaeriids does not provide us with index forms, their abundance in the fauna under analysis testifies better than any index forms in favor of its Devonian age.

Summing up the foregoing review of the stratigraphic position of a number of components of our fauna, we must recognize its age as Lower Devonian. The absence in it of typical Silurian elements does not permit assigning it a Gedinnian age and compels us to regard it as younger than the fauna of the Solov'ikha horizon. A more precise determination of age within the Eodevonian encounters difficulties: Leptaena bouei and Orthonychia acuta pass through the entire Lower Devonian, beginning with the Siegenian stage. Likewise, among the remaining forms only Spirifer geyeri serves as a weighty indication of the lower horizons of the Eodevonian; this indication is supported by the broad distribution in our fauna of Atrypa supramarginalis—a species also developed in the Gedinnian fauna of the Solov'ikha limestone. But on these grounds one can express only a supposition as to the Siegenian age of the rensselaeriid horizon.

However, in the present case, in refining the age of the rensselaeriid horizon we may make use of the relation, established by field observations, between it and the pseudotogatous horizon: their immediate contact and gradual transition, their belonging to the lower part of one (Ganino) formation, make it possible to supplement and refine the conclusion made above on the age of the rensselaeriid horizon on the basis of analysis of the fauna of the pseudotogatous horizon (see p. 35).

According to geographic character, the components of our fauna are distributed in three groups:

Eu—forms of European type:

Leptaena bouei (Barr.)
Camarotoechia cf. princeps (Barr.)
Spirifer geyeri Scup.
Cyrtina heteroclita (Defr.)
Orthonychia acuta (A. Roem.)
Platyceras altaicum n. sp.
Nuculoidea lodanensis (Beush.) var. altaica?
Cypricardinia cf. gratiosa Barr.

Am—forms of American type:

Stropheodonta patersoni Hall var. praecedens Cl.
Rhynchospirina (?) simulans n. sp.
Platyceras vulgare n. sp.
Platyceras nodoso-costatum n. sp.

En—forms of a specifically endemic type:

Rhynchotretina equivalvis n. gen. et n. sp.
Atrypa supramarginalis n. sp.
Cyrtina pygmaea n. sp.
Rensselaeriids—9 species.

Concerning the assignment of all our Rensselaerias to the En group, the following comment must be made: some of them show similarity to American and European species; however, as a whole they constitute a close indigenous association of forms, i.e., in the present case the above-mentioned similarity must be regarded as purely convergent. In numerical expression the distribution of our fauna among the three geographical groups is given below in the table:

Table 3

Geographical groups	identical	close	total
of the European type (Eu)	4	4	9 (6%)
of the American type (Am)	1	3	4 (16%)
indigenous type (En)	—	—	12 (48%)

From these figures we may draw the following conclusion: the geographical type of the fauna of the Rensselaeria horizon is mixed, with a predominance of indigenous and European elements and with American forms in a subordinate position; i.e., in this respect the given fauna is similar to the fauna of the Solovikha limestone. But there are also differences between them: in the fauna of the Rensselaeria horizon there was a noticeable strengthening of American elements—7.5% in the Solovikha fauna, 16% in the present fauna. This indicates that the connection with the American basins became stronger, and we shall note an even greater strengthening of this connection for the next moment of the Eodevonian, for the Pseudotogata time.

There is also a slight but essentially significant difference between the facial type of the faunas being compared. The Solovikha fauna has a typical Hercynian (Bohemian–Uralian) character and is enclosed in pure limestones; in the fauna of the Rensselaeria horizon there appear forms distributed not only in deposits of the Bohemian type, but also in deposits of the mixed Bohemian–Rhenish type (see Khalfin, 1940, p. 284). Such forms are, first of all, Leptaena bouei and Levenea sp., which occur in great abundance in the overlying marly Pseudotogata horizon; the pelecypods of the Rensselaeria horizon and, apparently, Stropheodonta patersoni praecedens should also be referred here. It is true that most of the forms (spiriferids, camarotoechiids, gastropods) have a clearly Bohemian facial type; likewise, Rensselaerias are almost absent in the marly formations of the Eodevonian of the Altai; nevertheless, the fauna of the Rensselaeria horizon no longer possesses the Bohemian–Uralian facial type in its pure form, but reveals the first approximation to the mixed Bohemian–Rhenish type so characteristic of the Eodevonian of the Altai.

In connection with this circumstance, let us make a few remarks on the question of the depressed character of our fauna; in this respect it also shows differences from the Solovikha fauna, namely: depression is a common property of all groups of the Solovikha fauna; in the fauna of the Rensselaeria horizon it has a selective character and affects only a certain (to be sure, very significant) part of the fauna.

Thus, our Spirifer geyeri and Orthonychia acuta, which are quite identical with European representatives of these species, have a sharply expressed depressed character, but differ in dwarf size; very indicative in this respect is also the pygidium Proetus sp., 2 mm long; the pelecypods (e.g., Actinopteria and Cypricardinia) also possess dwarf dimensions in comparison with close forms. All Rensse-

...leria give a very vivid picture of a stunted condition: the length and degree of curvature of the ventral beak, and the ratio of shell thickness to its length, indicate the adult state of individuals several times smaller than ordinary representatives of this genus. A large part of the fauna of the Rensselaeria horizon possesses such obvious features of a stunted condition.

Another group in this respect consists of ostracods and coelenterates, which I have not studied but which, judging by their dimensions, are normally or almost normally developed; with regard to the coelenterates, however, an important reservation must be made: they occur isolated from the rest of the fauna, i.e., they do not enter into the biocenosis analyzed by us. But even among the forms analyzed there are species sharply distinguished by their size—these are Leptaena bouei, Levenea, Stropheodonta pattersoni; partly Nuculoidea lodanensis must be placed here as well, since it has almost ordinary dimensions. It is very characteristic that Leptaena bouei and Levenea have a very broad distribution in the marly rocks of the Pseudotogatus horizon, in which brachiopods close to Stropheodonta pattersoni have also been found; and although representatives of the three species named above are half the size of their analogues in the fauna of the Pseudotogatus horizon, they nevertheless look like giants in comparison with the rest of the fauna of the Rensselaeria horizon, in particular in comparison with the other brachiopods. In other words, we have established a certain dependence: in the fauna studied, forms of the Bohemian facies type prove to be more stunted than forms of the mixed Bohemian–Rhenish facies type, although the latter also do not attain normal development (in particular, normal size). If we take into account that the limestone of the Rensselaeria horizon, from which the fauna I studied was extracted, is strongly contaminated by an abundant admixture of terrigenous material, then with a high degree of probability we may point to one of the factors that acted in a suppressive manner upon part of the fauna of the Rensselaeria horizon: apparently, the abundant influx of terrigenous material created unfavorable conditions for the existence of that part of our fauna which has the Bohemian type and whose analogues usually occur in purer limestones. I shall refrain from other assumptions that might be additionally advanced on this question, since, until additional data are obtained, only the cause indicated above for the stunted condition of our fauna may be regarded as more or less clarified. Above, in characterizing the fauna of the Solov′ikha limestone, I indicated that, in its stunted character, it is similar to one Silurian fauna of North America (p. 23); here it may be added that the cause which determined the stunted condition of the indicated American fauna, just as in our case, is an abundant influx of terrigenous material (see Stoneis, Catey, Grubbs, 1929).

3. Pseudotogatus horizon

The limestones of the Rensselaeria horizon are, in complete conformity, overlain by a thick sequence of marly rocks, chiefly sandstones, constituting the Pseudotogatus horizon of the Ganyan Formation; subordinate to these sandstones are thin interbeds of limestones, which are confined mainly to the lower part of the Pseudotogatus horizon and mark a gradual facies transition between the rocks of this horizon and the Rensselaeria horizon. The sandstones of the Pseudotogatus horizon have a greenish and yellowish-gray color; they contain a considerable admixture of calcareous material and effervesce vigorously under the action of acids; their weathered portions have a dark-brown color, a porous structure, and do not effervesce with HCl.

Organic remains in the sandstones of the pseudotogat horizon are confined to individual beds, in which they are usually abundant, but are completely absent from the thick horizons separating these beds. Ordinarily the organic remains are impressions, most often of isolated brachiopod valves. However, in areas not affected by weathering, the skeletal structures themselves are preserved (shell valves, carapaces, ossicles), but in this form they cannot be satisfactorily prepared; these remains may be used to establish the structure of the skeletal substance of the fossils, but to study morphology it is necessary to etch them with acid, as a result of which impressions of the external and internal surfaces are obtained, sometimes of ideal preservation, transmitting even very fine details of the morphology of the fossil skeleton.

Within the pseudotogat horizon we distinguish four faunistic beds, which in the section in Fig. 2 are numbered I, II, III, IV from bottom to top. Faunistic bed I lies 450 m from the footwall of the pseudotogat horizon; the distances (by thickness) between faunistic beds I—II, II—III, III—IV are respectively 150, 250, and 150 m. Beds III and IV are situated in that part of the section where the rocks of the pseudotogat horizon already alternate with apophyses of intrusive porphyry, the body of which occupies the position of higher beds of the Ganin Formation.

The fauna of the pseudotogat horizon is abundant and diverse in comparison with the fauna of the Solovykha and Rensseleria horizons; it presents a picture of flourishing, as may be judged both from the mass development of a number of forms and from the large size of individuals. The fauna as a whole is brachiopod; pelecypods occupy a subordinate but noticeable place in it; in places ossicles of sea lilies are fairly numerous; gastropods, cephalopods, tabulates (Aulopora), trilobites, and crustaceans are very rare. In the collection I have studied, brachiopods make up 70%; precisely among the brachiopods of the pseudotogat horizon we find a number of the most important forms, which make it possible to decide with considerable accuracy the question of the age of the Ganin Formation.

Table 4 shows the distribution by beds of the representatives of the fauna of the pseudotogat horizon that I have determined. From consideration of this table the following conclusions may be drawn:

a) the richest fauna is characteristic of bed III—here the majority of the determined forms were found;

b) owing to this, a considerable difference is observed between the fauna of beds I—II (in the further account, for brevity, called the “lower beds”), on the one hand, and beds III—IV (the “upper beds”), on the other;

c) this difference is further emphasized by the fact that forms passing from beds I—II into bed III and having mass development in bed I or II, in bed III yield this dominant place to others, for the most part—species that appeared suddenly in bed III;

d) among such forms appearing suddenly in bed III belongs the genus Leptodontella, the most characteristic and widespread form of the Altai Eodevonian;

e) only one species—Leptaena bouei Barr., which appeared already in the Rensseleria horizon, passes through all the beds of the pseudotogat horizon.

Let us give a brief faunistic characterization of each bed.

Bed I. The fauna is numerous but monotonous; of the five species found in this bed, three occur in mass development: Levenea taeniolata, Leptaena bouei, Atrypa lorana.

Bed II. The last three species, especially Levenea taeniolata, are also widespread in this bed; in addition, the first representatives of the genus Dalmanellopsis n. gen. appear here.

Distribution of the fauna of the pseudotogatus horizon by faunistic beds

Table 4

No.	Names of forms	I	II	III	IV	Collections of P. F. Krasnyakova
1	Crania korovini n. sp.	−	−	−	−	+
2	Levenea taeniolata n. sp.	⊕	⊕	+	−
3	Levenea cf. subcarinata (Hall)	+	−	−	−
4	Levenea altaica n. sp.	+	−	−	−
5	Dalmanellopsis septiger n. sp.	−	+	⊕	−
6	Proschizophoria cf. personata (Zeil.)	−	−	+	−
7	Leptaena bouei Barrande	⊕	+	+	+
8	Brachyprion aff. latus (Khalf.)	−	−	+	−
9	Brachyprion aff. naliwkini (Khalf.)	−	−	+	−
10	Leptodontella rotundata (Khalf.)	−	−	⊕	+
11	Leptodontella magna n. sp.	−	−	+	−
12	Schuchertella altaica Khalf.	−	−	⊕	+	+
13	Chonetes aff. rectispina n. sp.	−	−	−	−
14	Camarotoechia transversa Hall	−	−	⊕	−
15	Atrypa lorana Fuchs	⊕	+	+	−
16	Eospirifer pseudotogatus Khalf.	−	−	⊕	−
17	Delthyris perlamellosa Hall	−	−	⊕	−
18	Cyrtina heteroclita Defr.	−	−	+	−
19	Nuculoidea ex gr. N. lodanensis Beush	−	−	−	−	+
20	Praemyophoria latifrons Khalf. typ. praecedens	−	−	+	−
21	Toechomya krasnikovi n. sp.	−	−	−	−	+
22	Leiopecten rectangularis Khalf.	−	−	+	−
23	Tolmaia ex gr. T. squamosa Khalf?	−	−	−	−	+
24	Kionoceras altaicum n. sp.	−	−	+	−
25	Aulopora sp.	−	−	+	−
26	Phacops sp.	−	−	+	−
		5	4	19	3	5

NOTES: 1. Forms having a broad or mass distribution in the given faunistic bed are designated by ⊕.
2. In the column “Collections of P. F. Krasnyakova,” only those forms are marked that were not found in the collections of L. L. Khalfin.

Bed III. An abundant and diverse fauna; in comparison with the preceding beds, it is characterized by the appearance, in mass development or simply in considerable numbers, of representatives of the genus Leptodontella, of the species Schuchertella altaica, spiriferids, of the species Camarotoechia transversa Hall, and also by the mass development of Dalmanellopsis septiger and the appearance of fairly diverse pelecypods. Here Atrypa lorana and Levenea taeniolata are still encountered, but apparently do not pass higher.

Bed IV. A poor fauna, represented by three species passing upward from Bed III.

Thus, the spiriferids—Delthyris perlamellosa and Eospirifer pseudotogatus, after which the entire horizon received the name “pseudotogatus,” occur only in Bed IV and were not found in the “lower beds”; for the “lower beds” the development of large dalmanellids is characteristic (especially Levenea taeniolata); for the “upper beds,” in addition to the presence of spiriferids, an abundance of schuchertellas and leptodontellas is characteristic. On the basis of all that has been set forth, it appears entirely possible to distinguish, by faunistic characters, two zones (two sub-

horizon), which by their characteristic species may be called the teniolata and perlamellosa zones:

Table 5

Horizon	Zones	Beds
pseudotogatovian	perlamellosa	III–IV
pseudotogatovian	teniolata	I–II

The exact determination of the age of the pseudotogatovian horizon presents no difficulty, owing to the presence in its fauna of a number of important guide forms. If Leptaena bouei reliably indicates the Lower Devonian age of this fauna, then Camarotoechia transversa, Delthyris perlamellosa, and Atrypa lorana specify the position of our horizon in the Eodevonian: Camarotoechia transversa and Delthyris perlamellosa serve as guide fossils for the New Scotland horizon, which is the middle horizon of the Helderbergian Stage of North America. It should be noted that the Helderbergian Stage of North America is the equivalent of the Siegenian Stage of the European subdivision of the Devonian (and not of the Gedinnian Stage, as is not infrequently assumed in error).

Atrypa lorana is widespread in the Lower Devonian of Western Europe, but occurs especially often in the Siegenian shales of Hunsrück in the Rhenish Slate Mountains. In the Siegenian deposits there also occurs Proschizophoria personata, which, however, is known also from the more ancient—Gedinnian—deposits of the Ardennes and Artois; the ventral valves found in the pseudotogatovian horizon, determined by me as Proschizophoria cf. personata, are indistinguishable from the European representatives of this species, and if I have not identified them unreservedly, it is only because dorsal valves are lacking in my collection, i.e., this species is represented incompletely.

In complete agreement with this, although less authoritative, are the indications of our dalmanellids, which have a quite clearly expressed Helderbergian type and the closest analogues in the fauna of the lower Eodevonian of America and Europe. All the other forms in the fauna of the pseudotogatovian horizon do not contradict, and in part further confirm, the Siegenian age of this horizon; for example, our eospirifers have their closest analogues in the Siegenian deposits of Europe; likewise Kionoceras altaicum is closest to certain orthoceratids from the Koněprusy limestone of Czechoslovakia.

Thus, the stratigraphic indications of the guide forms and the general character of the fauna concordantly establish the stratigraphic position of the pseudotogatovian horizon: the pseudotogatovian horizon is of Siegenian age.

In establishing the geographic type of our fauna, we should note, first of all, the further strengthening in it of American elements; this increase in the role of American forms in the Altai Lower Devonian fauna was already noted by us for the fauna of the Rensselaeria horizon (in comparison with the Solovykha fauna). In the pseudotogatovian horizon the role of the American fauna reaches a maximum for the Lower Devonian of the Altai; this is expressed not only in the increase in the percentage (21%) of American-type forms in our fauna, but—and this is especially important—in the fact that American-type forms are here massively developed, and in number of individuals the American elements are not inferior to the European ones. This progressive strengthening of the influence of the North American zoogeographic province on the Lower Devonian fauna of the Altai can be explained only as the result of

of a gradual widening of communication between the Altaian and North American basins of the Lower Devonian. We shall return to these paleogeographic questions in the further discussion; here we shall limit ourselves to noting that, in later times of the Eodevonian epoch, this connection with the seas of North America again became greatly reduced.

The fauna of the pseudotogatous horizon is distributed among the geographical groups as follows:

Eu—forms of the European type:

Proschizophoria cf. personata (Zeil.)
Leptaena bouei (Barr).
Atrypa lorana Fuchs
Eospirifer pseudotogatus n. sp.
Cyrtina heteroclita (Defr.).
Nuculoidea ex gr. N. lodanensis (Beush.)
Praemyophoria latifrons Khalf. var. praecedens
Tolmaia ex gr. T. squamosa Khalf.
Kionoceras altaicum n. sp.

Am—forms of the American type:

Levenea taeniolata n. sp.
Levenea cf. subcarinata (Hall)
Dalmanellopsis septiger n. sp.
Camarotoechia transversa Hall
Delthyris perlamellosa Hall

En—forms of a specifically native type:

Crania korovini n. sp.
Levenea altaica n. sp.
Leptodontella rotundata n. sp.
Leptodontella magna n. sp.
Schuchertella altaica Khalf.
Chonetes cf. rectispina n. sp.
Taechomya krasnikovi n. sp.
Leiopecten rectangularis Khalf.

Co—forms of the cosmopolitan type:

Brachyprion cf. latus (Khalf.)
Brachyprion cf. nalivkini (Khalf.)

Table 6

Geographical groups	identical	close	total
of the European type (Eu)	3	6	9 (37.5%)
of the American type (Am)	2	3	5 (21%)
of the native type (En)	—	—	8 (33%)
of the cosmopolitan type (Co)	—	2	2 (8.5%)

The fauna of the pseudotogatous horizon, among the other Lower Devonian faunas of Northern Altai, has the smallest percentage of native forms and the largest percentage of American forms. Nevertheless, it also retains traces

a mixed type—American-European, with a significant role of local species.

However, while retaining this mixed type, it differs substantially from the fauna of the Rensselaer horizon in the following important features:

1) among the European-type components of the fauna, the predominance passes to forms that characterize the Rhenish facies type of the European Eodevonian: of the nine forms of the Eu group, five forms (Proschizophoria, Atrypa lorana, and pelecypods) are alien to the Bohemian-Uralian type; at the same time, our fauna also contains such forms as Leptaena bouei and eospirifers, which are equally alien to the Rhenish type; i.e., the fauna has a mixed Bohemian-Rhenish type.

2) within the composition of the fauna of the pseudotogatov horizon, characteristic native forms begin to occur in mass development, among which the genus Leptodontella must be named first of all.

Thus, the fauna of the pseudotogatov horizon, in stratigraphic terms, is characterized by Siegenian age; in geographic terms, it is the oldest representative of the leptodontellid fauna; in facies terms, it possesses a mixed Bohemian-Rhenish type.

In conclusion, let us dwell on the question of the origin of this fauna and its connection with the fauna of the older and younger members of the Altai Eodevonian. The appearance in this fauna of American and European species is understandable: they are immigrants that entered the Altai basin from the known seas of Europe, Central Asia, and America. In the process of this migration there evidently also arose those forms that vicariate with American and European species and that we have placed in the geographic groups Eu, Am, and Co. But the appearance of the group of this fauna most interesting to us, the group of native species, in particular the genus Leptodontella, remains unexplained and seems sudden: this genus and the forms accompanying it appear suddenly and in mass quantity in the III bed of the pearl-mellose zone of the pseudotogatov horizon. In the Rensselaer horizon we do not find their predecessors: in its fauna only Levenea sp. and Leptaena bouei, i.e., American and European immigrants, are such predecessors of the fauna of the pseudotogatov horizon.

Evidently, the genus Leptodontella and its companions penetrated at the above-mentioned moment into the Altai basin from some center, as yet unknown to us, where the initial formation of the leptodontellid fauna was taking place.

Our fauna has a far more definite connection with the fauna of the younger formations of the Altai Eodevonian; namely, with the fauna of the Kondrat’evka Formation our fauna shows clear points of contact. Five species—Cyrtina heteroclita, Leptaena bouei, Leptodontella rotundata, Atrypa lorana, and Leiopecten rectangularis—are common to the fauna of the pseudotogatov horizon and the Kondrat’evka Formation; the genera Brachyprion, Chonetes, Delthyris, Nuculoidea, Praemyophoria, Toechomya, and Tolmaia have close and probably related representatives in both faunas. Thus, the close connection between these faunas cannot be doubted. Much more distant and more general is this connection with the fauna of the Medvedevka Formation: there are no common species except Leptaena bouei and Cyrtina heteroclita; close forms occur only for the genera Levenea (the genetic connection is doubtful) and Brachyprion, while the characteristic Leptodontella links these faunas.

As we shall see below, the Kondrat’evka Formation is the next in age after the Gani Formation, which explains the greater closeness of their fauna. However, the time of formation of these formations is separated by a break in sedimentation; this break is associated with the retreat of the Lower Devonian

of the Altai sea, and this explains why, when it returned again within the limits of Northern Altai and rocks of the Kondrat’evka Formation began to be deposited in it, significant changes took place in its population: alongside forms inherited from the fauna of the pseudotogatov horizon, new immigrants appeared in great numbers, new associations of fossils, the predecessors of which we did not find in the pseudotogatov horizon.

4. Paramnigenia Horizon

The upper part of the section of the Devonian deposits of Ganin Brook, which I distinguish under the name of the Paramnigenia horizon, is of exceptional interest, despite its simple lithology (the same greenish-gray marly sandstones) and its scanty fauna. Analysis of this fauna, despite its imperfect preservation, makes it possible to establish the final stages in the formation of the Ganin Formation, the character of its upper boundary, and also reveals to us an entirely new group of Devonian fauna, nowhere previously encountered.

The fauna in this horizon occurs in the form of impressions, usually of an unattractive appearance: streaks of lime and iron oxides, which give a mottled character to the bedding surfaces on which the shell impressions are found, in many cases not very distinct in themselves, make these impressions still less clear. However, by carefully etching these surfaces with hydrochloric acid, one can bring out the manifestation on them of numerous impressions, which prove to be impressions of isolated valves of lamellibranch shells. Only a few of these impressions are complete and sufficiently well preserved to permit the following determinations:

1. Amnigenia altaica n. sp.
2. Paramnigenia bicarinata n. sp.
3. Paramnigenia ussovi n. sp.
4. Laurskia attenuata n. sp.
5. Laurskia ovalis n. sp.
6. Laurskia lata n. sp.
7. Modiomorphella korovini n. sp.
8. Modiomorphella sphenotiformis n. sp.
9. Modiomorphella simulans n. sp.
10. Obrutchevia prima n. sp.

This small list does not exhaust the composition of the fauna of the Paramnigenia horizon: on the rock specimens of this horizon that I have, there is a whole series of incomplete impressions of valves of certain forms, obviously distinct from those listed above, but I cannot describe and name them because of the complete fragmentary nature of the remains belonging to them. Thus, a more complete study of this interesting fauna on the basis of more extensive collections is a promising task for future investigations; but even the ten forms that I have established in the collection available to me make it possible to draw a number of interesting and important conclusions.

The fauna of the Paramnigenia horizon is represented almost exclusively by pelecypods; in this respect it stands in sharp contrast to the fauna of the pseudotogatov horizon, in which brachiopods predominate, while mollusks occur rarely. Further, the wholly endemic character of our pelecypods is striking: all ten species analyzed are new; moreover, they do not even have any at all close analogues among the described faunas of other regions and countries. This circumst—

is due to the fact that, of the five genera among which these ten species are distributed, four are new, and only the genus Amnigenia Hall, represented by the species Amnigenia altaica, is known from the Devonian deposits of Europe and North America. An explanation of this extreme endemicity of our fauna will be given below.

A fauna represented exclusively by new species and, with one exception, by new genera naturally cannot provide reliable indications of the age of the rocks enclosing it. In this respect one could rely only on the genus Amnigenia, whose representatives are known from the Middle and Upper Devonian of Western Europe and the Upper Devonian of North America; all the remaining species and genera of our fauna have no analogues with which they could be compared stratigraphically. If the paramnigenia horizon had been encountered in isolation, determining its age would have been extremely difficult and, if possible at all, only approximate (presumably within the limits of the Devonian system). But in our case the question of the age of the horizon is resolved simply, since it crowns the Gani Formation, whose age is precisely established by the fauna—above all by the pseudotagot horizon; this makes it possible to establish the geological age of the peculiar pelecypod assemblage under consideration as well.

Far more interesting conclusions can be drawn about the facies nature of this fauna, and consequently about the character of the basin in which the formation of the Gani Formation was completed. In this respect the genus Amnigenia must be used first of all; representatives of this genus inhabited freshwater basins of the Middle and Upper Devonian: in Europe they are known from \(D_2\) and \(D_3\), in America from \(D_3\) (see Clarke, 1901a); these are the oldest freshwater mollusks known to us. Our material shows that representatives of the genus Amnigenia appeared already in the lower half of the Eodevonian. The emerging regularity in the distribution of this genus in space and time (Siberia—\(D_1\), Europe—\(D_2\) and \(D_3\); America—\(D_3\)) requires verification: at present we possess such scanty materials concerning the freshwater fauna of the Devonian period that they are clearly insufficient for establishing the details of the geographic distribution and migrations of this fauna.

The Altai amnigenias differ from the European and American ones not only morphologically and in age, but also in the conditions of existence, which is expressed, in particular, in the character of the biocoenosis of which they are a component. The living conditions of representatives of the genus Amnigenia were clarified in the cited work of J. M. Clarke. The distribution of the American Amnigenia catskillensis is confined to the Upper Devonian Oneonta Sandstone of the State of New York. These deposits “were accumulated in an almost or completely isolated freshwater or brackish body of water, separated from the open sea on the west by a low shoal”; on the seaward side of this shoal there lived an abundant marine fauna; to the east the Oneonta sandstones pass into the purely continental Catskill deposits; together with Amnigenia catskillensis no other forms occur, and in the Oneonta sandstone there are no marine forms at all, with the exception of remains of orthoceratids, which were occasionally carried by currents from the open sea (Clarke, op. cit., pp. 199–200). Further noting that the occurrence of two known European species of Amnigenia is associated with the deposits of the Old Red Sandstone, J. M. Clarke states that all three species of amnigenias are confined to deposits of the same character, namely “sandstones and sandy shales containing remains of land plants, but entirely devoid of remains of marine organisms” (Clarke, op. cit., p. 200).

Under substantially different conditions are found the remains of the amnigenias and the rocks enclosing them in the Altai. Here Amnigenia altaica is an ingredient of a diverse biocoenosis, although one consisting chiefly of pelecypods; the deposits in which this biocoenosis is buried are, in an obvious way, connected with marine deposits, crowning the latter. Having noted these differences from the North American and European deposits with Amnigenia, let us continue the facies analysis of our fauna. In doing so we encounter considerable difficulties, since the other four genera of our pelecypods are new; nevertheless, even in considering these new forms, one can obtain essential data for judging the question that interests us.

The genus Paramnigenia appears to me to have genetic relations to the genus Amnigenia (perhaps through an as yet unknown common ancestor within the marine fauna of \(S_2\) or \(D_1\)). Morphologically, the shell of Paramnigenia may be derived from the shell of Amnigenia by shifting the umbones toward the anterior margin to their subterminal position, with a corresponding shortening of the anterior end of the shell, and by a sharp development of an umbo-ventral depression with a corresponding development of a sinus on the ventral margin. It may be assumed that the genus Paramnigenia inhabited the same conditions as the amnigenias related to it.

The genus Laurskia, as has been clarified elsewhere (Part II), is the Devonian analogue of the Meso-Cenozoic dreissensiids and has no other similar forms either in Paleozoic or in younger faunas. We have grounds to assume that representatives of the genus Laurskia inhabited the same conditions in which the dreissensiids lived and live; we are led to this not only by the morphological similarity between these genera, but also by the already elucidated example of Amnigenia and Anodonta (Clarke, 1901a), which, as is known, have striking morphological similarity and identical conditions of existence. This example is all the more valuable for us because in our fauna Laurskia is a companion of Amnigenia, just as in a number of younger faunas (beginning with the Cretaceous) Dreissensia is a companion of Unio and Anodonta in freshwater biocoenoses.

With regard to the two remaining genera of our fauna that have not been considered—Modiomorphella and Obrutchevia—the following may be said: they have no sufficiently close analogues either in freshwater or in marine fauna, but it is nevertheless more probable that they are connected with the marine pelecypods grouped in the genus Modiomorpha Hall; that is, while not being typical marine forms, they nevertheless to some extent impart a marine character to the biocoenosis under consideration.

In addition to the pelecypods characterized above from the facies standpoint, remains of trilobites occur in the deposits of the paramnigenian horizon, namely—a small-sized pygidium of some representative of the family Proetidae, and isolated librigenae. Finally, remains of orthoceratids are occasionally found. The presence of trilobites, even if only in the form of a single form, undoubtedly indicates a connection of the basin in which the deposits of the paramnigenian horizon were formed with the sea. As for the remains of orthoceratids, they most probably have a necroplanktonic character; these shells were carried into the Altai lagoonal basins by currents from the Siberian Sea (p. 120). The complete absence of coelenterates, brachiopods, and marine pelecypods—groups so widely distributed in the underlying pseudotogat horizon—as well as the character of the pelecypods of our fauna outlined above, indicates that this fauna is a Lower Devonian fauna of a lagoonal facies. The circumstance that, until now, representatives of the genus Amnigenia had been found only in purely freshwater deposits does not contradict this conclusion. The genus Amnigenia evidently has some ancestor among

marine pelecypods; moreover, in the course of the evolution of this group of mollusks, the transition from a marine environment to a freshwater one could not have bypassed the lagoonal facies. There is nothing surprising in the fact that our Altai amnigeniids, which are the oldest known, are still found in this facies; in the present case we see a fauna that had left the marine environment but had not yet reached a freshwater one. We know that later, in the Middle and Upper Devonian, amnigeniids inhabited freshwater basins, but their Lower Devonian companions did not follow them into fresh waters.

Thus, the paramnigenian horizon contains remains of representatives of a lagoonal Lower Devonian pelecypod fauna, a fauna with absolutely no analogues among those previously described. At present one can only state the fact of the existence of such faunas in the Lower Devonian and characterize one of them, which has become known to us, but very little can be said on the question of its origin. In our case only the following general propositions can be stated:

1) with the shallowing and freshening of the marine basin (in the present case—the Tanin basin), the Lower Devonian marine pelecypod fauna proved capable of separating from its composition forms which, evolving under the changed conditions, populated the newly arisen lagoonal basins;

2) this evolution toward adaptation to life in a freshened body of water proceeded in parallel along several branches and in some of them quickly led to the appearance of specialized forms, for example—Laurskia (development of an apical septum, as in Dreissensia) or Obrutchevia (development of an apical blade, as in Nyculites);

3) as a result of the development of this fauna, forms arose that proved to be morphologically similar to pelecypods that appeared much later, in the Meso-Cenozoic:

Amnigenia Hall (D)—Anodonta Cuv. (Tr—Rec.)
Laurskia n. gen. (D₁)—Dreissensia Ben. (Cr—Rec.)

But we cannot say which forms in the marine fauna of the Lower Devonian are the ancestors of the lagoonal pelecypods; in our particular case we cannot indicate, within the fauna of the pseudotogato horizon, the ancestors of the fauna of the paramnigenian horizon. I believe that the natural explanation of this circumstance is the following: the fauna of the pseudotogato horizon is a typical fauna of the open sea; evidently, in the same basin, but in its shallower, coastal parts, there lived a fauna of different composition, which as yet remains unknown to us. It is precisely this fauna, which in composition should have been closer to the fauna of the paramnigenian horizon than the fauna of the open sea, that must first have experienced the influence of the incipient shallowing and freshening of the basin, i.e., must have been the first to enter upon the path of reorganization in relation to the changing environmental conditions. Thus, I consider that the pelecypods of the paramnigenian horizon trace their roots to a fauna unknown to us, synchronous with the fauna of the pseudotogato horizon. This is why in these two horizons—the pseudotogato and the paramnigenian—we encounter faunas that are not genetically connected, while the pelecypods of the paramnigenian horizon seem to be a cryptogenic group.

The lagoonal fauna of the paramnigenian horizon is sufficiently differentiated and already contains specialized types within its composition. The further fate of this fauna is unknown to us; possible considerations on this question have been examined by me in a separate work devoted to clarifying the relationships of our fauna to the lagoonal faunas of the Upper Paleozoic.

Summarizing all that has been said above, we may draw the following conclusions. The Ganino Formation, composed in its lower and middle parts of marine sediments, is capped by deposits of a lagoonal facies that constitute the paramnegenic horizon. Thus, this horizon marks the moment of significant shallowing of the Ganino Lower Devonian basin and completes a certain cycle of sediment accumulation that led to the formation of the rocks of the Ganino Formation. This shallowing of the basin, with the subsequent interruption in the deposition of sediments, was caused by a certain upward movement of this part of the lithosphere. As we shall see below (p. 123), this movement was short-lived and was replaced by a new subsidence, the return of the marine basin into the limits of Northern Altai, and the renewal of its fauna—these will already be the deposits and fauna of the Kondratievka Formation, at the base of which lies a basal conglomerate. These tectonic movements between the Ganino and Kondratievka formations are the expression of a certain phase of tectogenesis which, following M. A. Usov’s method of naming such phases, may be called the Ganino phase of tectogenesis (see Table 18).

III. Lower Devonian of the Kuyagan District

Devonian deposits are significantly developed in the basin of the middle course of the Peschanaya River. However, the literature materials on these deposits are very scanty: apart from several of my articles, in which I briefly characterized part of the Devonian formations of this district and their fauna (Khalfin, 1935; 1939; 1940; 1944), the published data consist only of indications of the presence of Devonian deposits with fauna near one or another populated locality (see p. 72).

From these indications, of course, it is impossible to form a complete conception of all the Devonian deposits of the district; one can only say that they are expressed by different facies and probably have different ages. Since I also do not have the opportunity to use certain unpublished materials (reports of geological parties that worked in this district), I cannot set myself the task of giving a complete summary of the Devonian of the Peschanaya River basin; in what follows I shall base myself on my own observations, which were made during the summer field work of 1930 and 1932, and chiefly on the detailed study of the extensive fauna that I carried out, with interruptions, over ten years.

I studied Devonian deposits developed at several points south of the village of Kuyagan; they proved to belong to three formations of different ages—the Kondratievka ($D_1^2$), Medvedevka ($D_1^3$), and Malaya Feya ($D_2^3$—$D_3^1$) formations. All these formations occur in close proximity, but isolated from one another, in the form of small remnants preserved in small grabens; all of them lie transgressively upon a certain effusive-sedimentary sequence, which henceforth we shall call the Kuyagan Formation. The close stratigraphic relations between it and the transgressive Devonian formations of the district, as well as the circumstance that, according to some data, the Kuyagan Formation should be assigned a Devonian age, compel me to begin the review of the Devonian deposits of the Kuyagan district with a brief characterization of this formation. This characterization cannot be exhaustive, since this formation was covered by my field observations only cursorily, because their task was the study of the faunistically characterized Devonian deposits of the district: the Kuyagan Formation interested me only as the substratum of the transgressive marine deposits of the Devonian. Nevertheless, even on the basis of these non-exhaustive field materials and without special petro-

...from a [[unclear: beginning of word]]graphic study of the rocks of this formation, it may be established that it is an original member of the stratigraphic scheme of the Altai, and reliable analogues of it in other regions of the Altai are not yet known; this circumstance prompts me to set forth the data at my disposal concerning the Kuyagan Formation, leaving their clarification and elaboration to further investigations.

Fig. 4. Schematic structural map of the vicinity of the village of Kuyagan. \(S_2\)—limestone-phyllite Upper Silurian. \(K\)—Kuyagan Formation. \(D_1^2\)—Kondrat’evka Formation. \(D_1^3\)—Medvedevka Formation. \(D_1^3\)–\(D_1^4\)—Mikhailovka Formation.

As for the Lower Devonian deposits of the Kuyagan region (the Kondrat’evka and Medvedevka formations), they have been studied by me in detail with respect to their fauna and their relationships both to one another and to the formations developed in neighboring areas; the corresponding materials are presented in detail below. Here it is sufficient to say that both these formations ob-

...give, by their composition (greenish marly sandstones and shales), a type typical of the Eodevonian of northern Altai and contain, in large quantity, remains of fossils belonging to the leptodontellid fauna. The Zhelin and Zigen deposits, faunistically characterized, have not yet been established in the Kuyagan district; they are probably partly represented by the Kuyagan Formation mentioned above.

1. Kuyagan Formation

I gave a brief characterization of this formation in 1935, calling it an effusive-sedimentary suite and assigning to it the age of the upper part of the Upper Silurian (Khalfin, 1935, pp. 14–15, 23–24). Recently Yu. A. Kuznetsov expressed the opinion that the effusive-sedimentary suite of the Kuyagan district described by me may prove to be an analogue of the Ongudai Formation of central Altai, whose age has not been precisely established, but is presumably Lower Devonian (Yu. Kuznetsov, 1939, p. 36).

The Kuyagan Formation is most fully developed south of the village of Kuyagan and north of the village of Aleksandrovka, where it composes the high watershed Cherny Ridge between the headwaters of the Bolshaya Tikhaya and Kuyagan rivers (the latter enters the Peschanaya River from the left); eastward, the Kuyagan Formation embraces the basin of the Gremishka River and crosses over to the right bank of the Peschanaya River (Fig. 4); from the south there is thrust over it, along a broad front, a limestone-phyllite unit \(S_2\). The body of the Kuyagan Formation is broken by disjunctions into small wedges, partly downfaulted: in these small grabens and troughs are the remnants of various Devonian formations.

Thus, the Kuyagan Formation forms a broad belt of nearly latitudinal strike, crossing the Peschanaya River immediately south of the village of Kuyagan. Within this belt the strike of the rocks of the Kuyagan Formation changes: in the western part there is a west–northwest strike with dip to the south; in the eastern part the strike becomes northeast, with dip to the southeast. Thus there is outlined an arc-shaped structure, convex to the south, of the belt of the Kuyagan Formation.

The composition of this formation can best be observed in crossing Cherny Ridge from the valley of the Bolshaya Tikhaya River into the valley of the Kuyagan River, for example along the routes: Kuyagan Log—Zavorotny Spring, or Mordovsky Log—Cherny Spring. In my field-observation diary it is recorded:

“The watershed of the Tikhaya—Kuyagan rivers is a sharp-crested (Alpine-type) ridge, in places forming sharp peaks and dissected on the southern side by deep ravines—small valleys of springs flowing into the Tikhaya River and beginning in swampy cirques and hollows situated at various elevations. Above the development of a deluvial apron, along the gentle southern slopes of the watershed at first extend ridges of alternating limestones, calcareous sandstones, clayey and clay-marly shales¹, having a NE strike and a steep dip to the SE. About 1½ km from the Tikhaya River the slope becomes considerably steeper; here it is strewn with rocky outcrops of green and lilac porphyrites, their tuffs and tuffites, strongly interbedded; their strike in general appears concordant with the strike of the sedimentary rocks named above.”

These effusives also compose the crest of Cherny Ridge; the effusives are represented for the most part by green, at times gray-violet and violet porphyrites, which are accompanied in large quantity by tuffs. On passing to the northern slope of Cherny Ridge, i.e., to the lower horizons of the Kuyagan Formation, we observe a successive decrease in the role of effusives in the composition of the formation and a corresponding increase in the quantity of its normally clastic components—shales and sandstones. These latter initially have a clearly pronounced character

tuffites and are connected by various transitions with tuffs. In the headwaters of the Chernyi spring (a right tributary of the Kuyagan River) there is a series of outcrops that excellently illustrate the interbedding of effusive flows with tuffaceous sandstones and shales; among the shales, variegated varieties attract attention—green, cherry-red, and violet. These rocks have a strike along azimuth 280°, i.e., the same as that of the overlying porphyrites, but dip southward less steeply (angle 45°). Still farther north, i.e., lower stratigraphically, the effusive elements in the Kuyagan Formation gradually disappear altogether, and its lower member is a thick unit of gray clay shales; excellent outcrops of this shale unit occur along the middle course of the Chernyi spring. These rocks are normal clay shales without signs of noticeable phyllitization, but they are extremely finely laminated; their color is bluish gray with a faint violet tint; their strike is 290°, and their dip is southward at an angle of 40°. In the upper part of the section of this shale unit along the Chernyi spring there are interbeds of dark-gray limestone. Thus, the crossing of the Chernyi Range gives a section of the following composition (from bottom to top):

a) clay shales;
b) interbed of dark-gray limestone;
c) interbedding of shales and porphyrites;
d) porphyrites and their tuffaceous associates.

This section is well maintained eastward along the Chernyi Range. I formed the impression that it represents a single sedimentary-effusive unit at least 4 km thick, which I call the Kuyagan Formation. It is possible that subsequent detailed studies will provide material for subdividing it, in particular for separating its upper effusive part.

The section of the formation described above (shales below, effusives above) is repeated east of the Peschanaya River, beyond the line of the large meridional fault that runs along the left side of this river south of the village of Kuyagan; this constancy of the section serves as evidence in favor of the assumption we have made—namely, that the Kuyagan Formation represents a sedimentary-effusive unit in which the lower part is composed essentially of clay shales, and the upper part of porphyrites and their tuffaceous derivatives.

The age and facial nature of the Kuyagan Formation cannot at present be established with exhaustive precision: its deposits, with the exception of the limestones lying in the upper half of the shale part, are devoid of fauna; in this same limestone interbed the fauna was found in the zone of folding (see below), where the limestones are crushed and marbleized. In them, corals of unsatisfactory preservation were encountered and remained unprocessed. Striking is the complete absence of organic remains in the clay shales of the Kuyagan Formation: in their general appearance and in the absence of noticeable metamorphism they are entirely similar to the shales of Devonian marine formations developed nearby; the sharp difference between them is the abundance of remains of marine organisms in the latter and the complete absence of any fossils in the shales of the Kuyagan Formation. This, of course, indicates that the shales mentioned were formed under different conditions, while the similarity of the upper, effusive-tuffite part of the Kuyagan Formation to the continental Ongudai Formation of the Central Altai (Yu. Kuznetsov, 1939, pp. 35–36) suggests that the Kuyagan Formation consists mainly of continental deposits; only the limestones mentioned above mark a moment of short-lived marine transgression, after which the deposition of the same clastic rocks continued under conditions of increasing effusive activity.

Until the discovery of a more satisfactory fauna in the limestone horizon and the study of this fauna, for determining the age of the formation

one can only make use of its comparison with neighboring deposits whose age is known. Its upper age limit is determined by the fact that the Kondrat’evka Formation \((D^2_1)\) lies transgressively upon it; that is, the Kuyagan Formation, being pre-Koblenzian, cannot be younger than the Gedinnian \((SD)\) or Siegenian \((D^1_1)\). At the same time, the rocks composing it—especially the clayey shales—are striking in their fresh appearance; this freshness is particularly pronounced if they are compared with the deposits of the Upper Silurian limestone-phyllite sequence, which is developed farther south and which has been thrust over a broad front onto the Kuyagan and Medvedev formations (Fig. 4). The clayey shales of this Silurian sequence have been transformed into typical phyllites and chlorite schists with an intense silky sheen, and the limestones into fine-grained marbles; conversely, the clayey shales of the Kuyagan Formation are very similar to the Middle Devonian shales of the Malafeevka Formation (see p. 80). This difference in the degree of metamorphism between the Upper Silurian sequence and the Kuyagan Formation is so great that it may well serve as an indication of the considerably younger age of the latter.

As already noted above, in 1935 I regarded the age of this formation as Upper Silurian, but younger than the age of the limestone-phyllite sequence; at that time I did not yet know the exact age of the deposits of Kondrat’evka Hill \((D^2_1)\) and Medvedev Log \((D^3_1)\) lying upon the Kuyagan Formation, nor had the Gedinnian and Siegenian deposits of the Anuy-Ganin graben been established. At present, having at my disposal the detailed stratigraphy of the Eodevonian of the Northern Altai, I am inclined to assign the Kuyagan Formation a Lower Devonian age. In this question I am guided by the following considerations: the clayey shales of the Kuyagan Formation, in their degree of metamorphism, do not differ from Devonian ones and differ sharply from Upper Silurian ones; before the deposition of the rocks of the Kondrat’evka Formation \((D^2_1)\), i.e., in pre-Koblenzian time, there was still a very long interval, corresponding to the Gedinnian and Siegenian stages and more than sufficient for the formation of the Kuyagan sequence of sedimentary-effusive rocks with their subsequent partial denudation before the deposition of the Kondrat’evka Formation. The absence in the Kuyagan area of faunistically characterized Gedinnian and Siegenian deposits, developed farther west in the Anuy-Ganin graben, permits the question to be raised of the possible presence in the Kuyagan area of some continental equivalent of them, which the Kuyagan Formation may have been. The great similarity of its upper, effusive-tuffaceous sequence to the Ongudai Formation, which K. V. Radugin (1941) and Yu. A. Kuznetsov (1939) tentatively assign to the Devonian, serves as an additional indication in favor of accepting a Lower Devonian age for the deposits of the Kuyagan Formation.

On the basis of the data and considerations set forth above, I regard the following definition of the Kuyagan Formation as most probable: it is, in the main, a continental sedimentary-effusive sequence that formed in the Kuyagan area, probably parallel with the deposition, within the Anuy-Ganin graben, of marine formations of Gedinnian \((SD)\) and Siegenian \((D^1_1)\) age; the limestone horizon of the Kuyagan Formation marks a short-term ingression of the sea into the Kuyagan area, having the character of an episode in the history of the formation of the continental sedimentary-effusive deposits described here. This conclusion may be presented in the form of Table 7 (see next page).

To complete the characterization of the Kuyagan Formation, I must briefly dwell on those changes undergone by its rocks near disjunctives. These changes are most vividly, naturally, expres—

Table 7

Stages	Anui–Ganin graben	Kuyagan district
Lower Kobenian ($D_2^1$)	Absent	Kondrat′evskaya Formation (marine deposits)
Zigenian ($D_1^1$)	Ganin Formation (marine deposits alternating with lagoonal deposits)	Hiatus Kuyagan Formation (continental effusive-sedimentary sequence with a marine horizon in the lower part)
Zhedinian (SD)	Hiatus Solov′ikha Limestone (marine deposits)	Hiatus Kuyagan Formation (continental effusive-sedimentary sequence with a marine horizon in the lower part)

…are found in the clayey shales of the lower part of the formation, which, near the lines of dislocation, are altered almost beyond recognition.

Along the left bank of the Peschanaya River, south of the village of Kuyagan, runs a line of major dislocation, along which (on its eastern side) a narrow wedge of ancient, probably Upper Silurian deposits has been brought to the surface; they are represented chiefly by chlorite schists and marbles, but also contain strongly altered effusives. Outcrops of these rocks occur along the left side of the valley of the Peschanaya River between its tributaries—the Maksimov and Tartykov springs (see Fig. 5). These deposits have a latitudinal strike with a dip to the south at angles of 50–70°; in some outcrops the crumpling of these rocks, the formation of small folds, and similar phenomena usually observed near major disjunctives are well expressed. In degree of metamorphism, and partly also in composition, these deposits may be compared with the above-mentioned limestone-phyllite sequence of the Upper Silurian, thrust over the Kuyagan and Medvedev formations from the south (see p. 64); I tentatively assign them an Upper Silurian age, but they may possibly prove to be older. West of the mentioned line of dislocation, clayey shales are distributed—

Fig. 5. Tectonics of the Kuyagan Formation near the disjunctive (schematic)

of the lower part of the Kuyagan Formation; they undergo interesting changes both in occurrence and in properties as they approach this disjunctive line (Fig. 5). These changes are best traced along the Kuyagan River and its right tributaries.

In the exposures along the right tributaries of the Kuyagan River, which enter it above (west of) Osipov Spring (Cherny and Zavorotny springs), the steady west-northwestern strike of the schists of the Kuyagan Formation is preserved; this is lost east of Osipov Spring: in the section along the Kuyagan River below Osipov Spring there is observed a frequent and abrupt change in the attitude of these schists, which prove to be gathered into small folds of northwestern and meridional strike. These disturbances in the occurrence of the schists are accompanied by a considerable increase in the degree of their metamorphism: they prove to be strongly chloritized, as a result of which they acquire a more intense green color and a strong silky luster. A very characteristic and persistent feature of these schists in the zone of crumpling is, corresponding to their very fine cleavage, a very fine but intense platy structure, which on the surfaces of schistosity is reflected in the form of fine corrugation. In the more deeply metamorphosed Silurian rocks exposed east of the line of disturbance, such platy structure and corrugation are absent. Among the crumpled schists described above there are interbeds of limestones, which show the corresponding metamorphism, being marblized.

The rocks of the Kuyagan Formation altered in this way mark a rather broad zone of crumpling, situated along the line of disturbance, to the west of the latter. Along the Kuyagan River, the crumpled schists are observed for a distance of more than 2.5 km; the western boundary of their development is Serapionov Log, which enters the Kuyagan River from the left a little west of the mouth of Osipov Spring. To the south this zone of crumpling narrows, thus having the outlines of a wedge; I traced it as far as Karaulnaya Hill, which is on the northern bank of the Gremishka River, entering the Peschanaya River opposite Kondratyevskaya Hill. Along with the above-indicated southward narrowing of the zone of crumpling directly adjoining the line of disturbance, to the west of it, in the upper reaches of Mitin Spring, another, less significant belt of similar alteration of the rocks of the Kuyagan Formation is noted. (Here, in particular, in crushed and marblized limestones, the poor coral fauna mentioned above was found.)

The broad zone of crumpling of the schists of the Kuyagan Formation, and the appearance on the left side of the valley of the Peschanaya River of older rocks alien to this formation, indicate the considerable dimensions of the meridional disturbance along which the valley of the Peschanaya River is oriented in this segment. This broad valley, filled with very recent deposits, conceals from us the details of the geological structure connected with the indicated disturbance. It may be asserted, however, that this disturbance is not a simple linear disjunction, but is accompanied by a number of subsidiary tectonic lines. This is indicated, first of all, by the unexpected appearance on the right bank of the Peschanaya River, amid the extent of the rocks of the above-mentioned Silurian wedge, of deposits of the Lower Devonian Kondratyevskaya Formation (Fig. 4). Probably subordinate to this same principal disturbance is also that local disturbance which, at the eastern end of Kondratyevskaya Hill, cuts off the rocks of the Kondratyevskaya Formation (see p. 51) and beyond whose line deposits of the Kuyagan Formation again crop out, not having undergone along this line such strong changes as along the disturbance described above.

In conclusion, let us dwell on clarifying the relations of the Kuyagan Formation to the younger marine Devonian deposits of the region. These relations are determined, first of all, by the circumstance that the Kuya-

…the Kuyagan Formation is the basement for Devonian formations of different ages: the Lower Koblenzian (Kondrat’evka Formation), Upper Koblenzian (Medvedevka Formation), and Givetian–Frasnian (Malafeevka Formation) deposits lie upon it transgressively and with angular unconformity (see Fig. 4). The material of all these Devonian deposits was, to a certain extent, borrowed from the rocks of the Kuyagan Formation as a result of their erosion and redeposition. This is especially reflected in the composition of the basal horizons of the transgressive Devonian formations: the cement of the basal conglomerates often has the character of a fine-clastic breccia and consists of diagenetically altered grus of the Kuyagan effusives; some sandstones from the lower part of the Medvedevka Formation acquire a graywacke character, containing white feldspar grains and small grains of dark-colored components borrowed from the underlying effusives of the Kuyagan Formation. It is probable that, in general, the marine Devonian deposits of the area are composed to a considerable degree of reworked material from the rocks of the Kuyagan Formation, from which they inherited their greenish colors.

Type section of the Kuyagan Formation: the crossing of the Chernyi Ridge along the route Medvedev Log—Chernyi Spring; standards of the formation: a) the section in the headwaters of Mordovskii Log (the relation of the Kuyagan Formation to the Medvedevka—D³₁); b) the section along the Kuyagan River from the mouth of Osipov Spring to the mouth of the Kuyagan River (changes in the rocks of the Kuyagan Formation in the zone of folding); c) the headwaters of the Mitin and Maksimov springs (fauna of the limestone horizon).

2. Kondrat’evka Formation

This formation, characterizing a definite stage in the Devonian history of the Northern Altai and containing a fauna unique of its kind (in richness and diversity), is known to us, unfortunately, only from two of its outliers preserved among the deposits of the Kuyagan effusive-sedimentary formation: one of them forms the southern slope of Kondrat’evka Hill in the vicinity of the village of Kuyagan, the other is situated some three kilometers southeast of this hill. By fortunate chance, the first of these outliers gives us a section that permits observation of the conglomerate lying at the base of the formation and is excellently characterized faunistically; the second, a very small spring exposure of this formation in which we did not find organic remains, additionally illustrates the conditions of occurrence of the formation in relation to the Kuyagan effusives.

Strangely enough, the large rocky outcrops of Kondrat’evka Hill, containing an exceptionally rich fauna, long remained unexamined, and in pre-revolutionary works (and likewise in the materials of V. P. Nekhoroshev, see 1932, 1932a) there are no references to them or to their fauna. The credit for the discovery of the fauna of the Kondrat’evka Formation belongs to I. P. Komarov, who collected an extensive collection, which in 1930 was delivered by him to the West Siberian Geological Administration and later was handed over to me for study. In 1935, in my summary of the stratigraphy of the Devonian deposits of the Altai, I gave a brief characterization of this fauna on the basis of preliminary identifications of some of its groups and established its Lower Devonian age. Later I published a more detailed characterization of the pelecypods of the Kondrat’evka Formation, on the basis of whose study the age and the facies and geographic types of this fauna were refined (Khalfin, 1940). In the paleontological part of the present work, the brachiopods, trilobites, and pelecypods of the Kondrat’evka Formation are described in detail.

“Kondrat’evka Hill is an uneven-sided hill elongated in a latitudinal direction, situated on the right bank of the Peschanaya River at its short latitudinal bend, immediately south of the village of Kuyagan. The southern slope of the hill, facing the river, is steep—

…steep, in places almost precipitous, rocky. The northern slope is very gentle, turfed over and plowed almost up to the very break in slope to the south. There are no outcrops on the northern slope.

The southern front of the hill extends for a kilometer and a half; over almost this entire distance there are rocky exposures of sandy-clayey Lower Devonian rocks, exposed by the Peschanaya River almost along strike. Throughout this exposure the bedding elements of the rocks remain fairly constant: strike—\(290^\circ\); dip to the SW at an angle of \(70^\circ\).

Since the front of this exposure in plan forms a gentle arc, convex to the south, it is natural that the highest horizons emerge in the middle

Fig. 6. Kuyagan and Kondrat’evka formations near Kondrat’evka Hill

Legend: massive limestone; granite; \(a\)—shales of the Kuyagan Formation; \(в\)—effusive rocks of the Kuyagan Formation; Kondrat’evka Formation.

part of the exposure. The underlying beds are most fully exposed in the upper part of the exposure (upstream along the Peschanaya River).

The entire sequence described is composed of terrigenous rocks. Moving from the upper end of the exposure toward its middle part, one can trace a change in the character of the rocks with respect to the grain size of their constituents—from conglomerates to fine-sandy and clayey formations.

The conglomerates, distributed together with sandstones in the lower part of the sequence, contain almost exclusively quartzite pebbles. In most cases the pebbles are rounded, but angular fragments also occur. The color of the quartzites is white, greenish-gray, and black. Much more rarely, limestone occurs among the quartzites in the conglomerate pebbles. The cement of the conglomerate has a greenish-gray color and consists of products of destruction of effusive-tuffaceous…

rocks of the Kuyagan Formation, upon which the deposits of Kondrat’evskaya Sopka lie transgressively.

As one moves toward the hanging side of the formation (i.e., moving downstream along the Peshchanaya River), the conglomerates are replaced by sandstones, and then by dark, bluish- and greenish-gray, very dense sandy-clayey and clayey rocks, predominating in the upper (stratigraphically) part of the exposure.

The entire sequence possesses a high degree of regular bedding. Some thin interbeds contain numerous organic impressions.

The rocks of the sequence characterized here are broken by a system of joint planes and, on weathering, disintegrate into characteristic irregular polyhedra of various sizes (Khalfin, 1935, pp. 22–23). Such polyhedra form large talus accumulations at the foot of the rocky exposures of the formation, and also occur in the bed of the Peshchanaya River.

The above-characterized section of the Kondrat’ev Formation is an isolated element in the geological structure of the area: on the east and on the west it is bounded by fault lines which probably join south of Kondrat’evskaya Sopka, somewhere beneath the cover of alluvial deposits of the broad valley of the Peshchanaya River.

The eastern contact of the deposits characterized here with the deposits of the Kuyagan Formation is shown in Fig. 7; from this drawing it is evident that the deposits of the Kondrat’ev Formation abut eastward against a fault line, beyond which are developed deposits extending almost perpendicular to the strike of the Kondrat’ev Formation and forming small folds near the fault line. The rocks developed east of the fault line indicated in Fig. 7 differ from the rocks of the Kondrat’ev Formation not only in their mode of occurrence, but also in their texture: these are thinly laminated (more precisely, fissile) dark-gray clayey shales; their extremely fine fissility is the complete opposite of the density and massive character of the rocks of the Kondrat’ev Formation. However, despite such fine slaty cleavage, these rocks have the gray color and appearance of normal clay shales, without any signs of the considerable metamorphism characteristic of the Silurian shales of the region. In my field-notes diary I recorded the following characterization of the eastern end of Kondrat’evskaya Sopka:

\(D_1^2\)—Kondrat’ev Formation

\(K\)—Kuyagan Formation

Fig. 7. Eastern end of Kondrat’evskaya Sopka

“Along the eastern part of Kondrat’evskaya Sopka—in nature this is a small hill, separated from the sopka itself by a ravine—there is a road. Along the road itself crop out clayey shales standing on edge; they are extremely finely fissile—like some sort of crumbs of shale chips standing on edge; their strike is northeast, dip to the SE at an angle of \(15^\circ\)... The thickness of the rocks of this exposure is considerable, apparently over 100 m; the composition of these rocks: in the northwestern part of the exposure (lower stratigraphically)—clayey shales; in the southwestern (upper stratigraphically), among the same gray and greenish-gray shales, there are interbeds of sandstones, three thin interbeds of dark-gray somewhat calcareous limestone, and two very thin flows of green porphyrite. Farther east (higher stratigraphically) there is a ridge of fissile tuff breccia, which lies conformably with the shale sequence characterized above.”

Still farther to the southeast there is an effusive-tuffaceous sequence composed of fissile green and lilac porphyrites and their tuffs; it makes up the hill Berezovy Mys (see Fig. 6), forming the right side of the valley of the Peshchanaya River. The strike of the rocks of this effusive sequence is also

northeast, dipping to the SW at an angle of 70°–80°. Thus, from the east the rocks of the Kondrat’evka Formation are bounded, along a tectonic contact, by a thick sequence consisting of thin-bedded argillaceous shales below and greenish-lilac porphyrites above; in it it is not difficult to recognize the Kuyagan Formation of the Chernyi Range described above. It should be noted, incidentally, that its shales near the tectonic boundary with the Kondrat’evka Formation are crumpled into small folds (Fig. 7), like those that characterize the zone of folding on the left bank of the Peschanaya River (see p. 46 and Fig. 5). In the present case, however, the shales fully preserve their normal appearance and show neither chloritization nor schistosity; this indicates that the disturbance at the eastern end of Kondrat’evka Hill is of considerably smaller scale than the disturbance described above along the left side of the Peschanaya River; for this reason I regard the former merely as a phenomenon accompanying the latter.

Tracing the described section of the Kuyagan Formation to the southeast, we pass from Beryozovyi Mys Hill, composed of effusives, into the valley of an unnamed stream that flows into the Peschanaya River above this hill (Fig. 6). This turf-covered little valley greatly obscures the very important relationships between the deposits developed along its sides and in its headwaters: along its right side the exposures of effusives of the Kuyagan Formation come to an end; in its upper reaches there crops out a massive barren fine-grained white and light-gray limestone, which has been subjected to contact alteration by hornblende granite; along the left side of this little valley, however, there are exposed rocks which in their external appearance are completely indistinguishable from the rocks of Kondrat’evka Hill—this is the second preserved remnant of the Kondrat’evka Formation, mentioned above at the very beginning of the description of this formation. From the diary:

“Here there are exposed rocks identical with the deposits of Kondrat’evka Hill—sandy-argillaceous massive rocks, more or less calcareous; they are likewise broken by numerous flat joints, giving the exposure a peculiar stepped-rubblestone appearance; the color is the same, and bedding is likewise weakly expressed.”

The very characteristic features of the rocks of the Kondrat’evka Formation make it possible to recognize them without error in the exposure described, although no fauna has been found here either; among these clastic deposits there occur here gray bedded limestones, in which fauna likewise has not been found. These rocks have a northeastern strike and dip to the southwest at an angle of 30°–40°; that is, at this locality, in strike, they are generally concordant with the deposits of the Kuyagan Formation, but they dip (in the same direction) more gently. Their contact with the Kuyagan Formation falls precisely in the valley of the little stream mentioned; in addition, in the upper reaches of this small valley massive limestones crop out, whose position also remains unclear; thus the section described (Fig. 6) lacks exposures at the most critical place. In it the lower horizons of the Kondrat’evka Formation are not exposed, but in its principal section (Kondrat’evka Hill) they are present and are represented by conglomerate; in the pebbles of this conglomerate, alongside predominant quartzites, there is also gray limestone, and the green cement of the conglomerate contains fragments of effusives of the Kuyagan Formation. Without setting myself the task of deciding the question of the nature of the massive limestones appearing in the section analyzed—which is not part of my task and for which it would first of all be necessary to trace them along the strike of the formation, i.e., to the northeast—we may, on the basis of the data presented above, accept that the Kondrat’evka Formation lies transgressively and with angular unconformity upon the deposits of the Kuyagan Formation (and likewise upon limestones of unclear stratigraphic position, but more ancient than the Kondrat’evka Formation). In fair-

...the validity of the conclusion I have drawn; in particular, the same is confirmed by the quite obvious relationship to the Kuyagan Formation of another Lower Devonian sequence (the Medvedevka), which is developed nearby.

We examined the geological setting southeast of Kondrat’evskaya Sopka; we established that the Lower Devonian deposits of this hill are truncated on the east by a disjunctive fault. In a few words we shall characterize the western boundary of these deposits: here they abut against the broad valley of the Peschanaya River, while along the left side of the latter, along the strike of the Lower Devonian rocks of Kondrat’evskaya Sopka, deposits of the Upper Silurian tectonic wedge crop out, brought to the surface in connection with the major meridional dislocation described above (p. 47). Thus, the deposits of Kondrat’evskaya Sopka proved to be squeezed between two dislocations, surviving in a small downthrown area in the form of an isolated island among more ancient deposits (chiefly of the Kuyagan Formation).

We now turn to consideration of the fauna of the Kondrat’evskaya Formation. This fauna, in its richness and diversity, occupies an outstanding place among the Lower Devonian faunas of the USSR; it is represented by almost all groups of invertebrates, but brachiopods, trilobites, and pelecypods are most highly developed in it; these have been subjected by me to detailed study and are described in detail in the second part of the present work. In addition to the three groups indicated, gastropods and some Tabulata are considerably developed in our fauna; crinoid ossicles are abundant, but calyces have not been found; cephalopods, bryozoans, and receptaculitids occur rarely. The general list of forms determined by me from the deposits of the Kondrat’evskaya Formation is as follows:

1.* Chonetes rectispina n. sp.
2. Chonetes bistriata n. sp.
3. Chonetes cf. sarcinulata Schl.
4.* Leptaena bouei (Barr.)
5.* Brachyprion speranskii n. sp.
6. Brachyprion speranskii var. aequistriata
7. Brachyprion n. sp.
8. Stropheodonta sedgwicki (V. et A.)
9.* Leptodontella rotundata n. sp.
10. Leptodontella cf. acuta n. sp.
11. Schuchertella cf. altaica Khalf.
12. Isorthis cf. trigeri (Vern.)
13.* Wilsoniella prima Khalf.
14. Camarotoechia tridens n. sp.
15. Eatonia glabra n. sp.
16. Delthyris cf. koegeleri (Scup.)
17. Delthyris cf. carinthiaca (Frech)
18. Delthyris cf. robusta Barr.
19. Delthyris perlamellosa (Hall) var. altaica Khalf.
20. Cyrtina heteroclita (Defr.)
21.* Atrypa lorana Fuchs
22. Harpes sp.
23. Bronteus cf. angusticeps Barr.
24. Bronteus altaicus n. sp.
25. Bronteus cf. altaicus n. sp.
26. Bronteus regularis n. sp.
27. Bronteus aff. regularis n. sp.
28. Bronteus sp.
29. Cyrtosymbole pulchella n. sp.

1. Cyrtosymbole conica n. sp.
2. ” cf. pulchella n. sp.
3. Proetus carinatus n. sp.
4. Lichas (Euarges) parva n. sp.
5. Acidaspis (Leonaspis) punctata n. sp.
6. Calymene sp., ex gr. C. blumenbachii Brogn.
7. ” sp.
8. Crotalocephalus sternbergi (Boeck.)
9. Cheirurus strabo Web.
   39.* Probolium altaicum (Khalf.)
   40.* Phacops subcristata n. sp.
10. ” sp.
11. Pseudaviculopecten n. sp.
12. Pterinopecten niobe (Barr.) var. altaica Khalf.
    44.* Leiopecten rectangularis Khalf.
13. Actinopteria sp.
    46.* Tolmaia squamosa Khalf.
    47.* Mytilarca plethomytiloides Khalf.
14. ” nana n. sp.
15. ” sp. cf. M. plethomytiloides Khalf.
    50.* ” elongata Khalf.
16. ” similis n. sp.
17. ” terebratuloides n. sp.
18. ” tenuis Khalf.
19. ” gibbosa n. sp.
20. Plethomytilus pseudoconspicuus Khalf.
    56.* Myalinopterella curvirostris Khalf.
21. ” ovata n. sp.
22. ” n. sp.
23. Modiomorpha obliqua n. sp.
24. ” ellipsis n. sp.
25. Modiomorpha (?) n. sp.
26. Mytilomorpha sp.
27. Nuculoidea lodanensis (Beush.) var. altaica Khalf.
    64.* Ctenodontella propinqua Khalf.
28. ” propinqua Khalf. var. intermedia Khalf.
29. ” ” ” n. var. gibbosa
30. ” macrodiformis Khalf.
31. ” subquadrata n. sp.
32. ” carinata n. sp.
33. ” parallela n. sp.
34. ” circularis n. sp.
35. Tancrediopsis elegans Khalf.
36. Cleidophorus regularis Khalf.
37. ” altaicus Khalf.
    75.* Toechomya subcircularis Khalf.
38. ” beushauseni (Maur.)
39. ” cf. intermedia (Dham.).
40. ” orthogonalis n. sp.
41. ” sibirica n. sp.
    80.* Praemyophoria acutirostris Khalf.
42. ” latifrons Khalf.
43. Glossites altaicus n. sp.
44. ” similis n. sp.
45. ” sibiricus n. sp.
46. Grammysia sp.

1. Cypricardinia contexta Barr.
2. “ rectangularis Khalf.
   88.* Paracyclas edentalis Khalf.
3. Conocardium sp.
4. ? Buchiola sp.
   91.* Archaeocardium scrobiculare Khalf.
5. “ scrobiculare Khalf. var.
6. Zygopleura n. sp., aff. Z. devonicans (Barr.)
7. Stylonema n. sp., aff. S. solvens (Barr.)
8. Cyclonema n. sp., aff. C. guilleri Oehl.
9. Turbocheilus n. sp., aff. T. immaturus (Barr.)
   97.* Pleurodictyum cf. problematicum Goldf.
10. Striatopora sp.
11. Aulopora sp.

The fauna of the Kondratyevka Formation is characterized by an extreme unevenness in the quantitative development of its various components; of the above list of 99 names, only the following 19 forms¹ show mass development:

1. Chonetes rectispina
2. Leptaena bouei
3. Brachyprion speranskii
4. Leptodontella rotundata
5. Wilsoniella prima
6. Atrypa lorana

} brachiopods

1. Probolium altaicum
2. Phacops subcristata

} trilobites

1. Leiopecten rectangularis
2. Tolmaia squamosa
3. Mytilarca plethomytiloides
4. Mytilarca elongata
5. Myalinopterella curvirostris
6. Ctenodentella propinqua
7. Toechomya subcircularis
8. Praemyophoria acutirostris
9. Paracyclas edentalis
10. Archaeocardium scrobiculare

} pelecypods

1. Pleurodictyum cf. problematicum—a coral of the group Tabulata.

The remaining 80 forms are sparsely distributed, and most of them occur as single specimens (for more on this property of the leptodontellid fauna, see p. 124).

The fauna characterized here, together with the fauna of the Medvedevka Formation, most typically expresses the features of the Altai zoogeographic province of the Lower Devonian, whose population consisted of the leptodontellid fauna. In our fauna, the overwhelming quantitative predominance belongs to local elements: if, from the above list, one excludes 11 forms determined only to genus, then of the remaining 88 there are 71 local forms (including in this figure 6 forms determined with the sign “cf.” in relation to local species); this means that endemic forms constitute somewhat more than 80% of the total number of determined species and

¹ In the list they are marked with asterisks.

varieties. This is the leptaenodontelloid fauna in its typical expression; a detailed characterization of it is one of the tasks of this work.

From my entire, fairly extensive collection, I have been able to identify fully with species known from other regions and countries only 8 forms:

Leptaena bouei (Barr.)
Stopheodonta sedgwicki (V. et A.)
Cyrtina heteroclita (Defr.)
Atrypa lorana Fuchs
Crotalocephalus sternbergi (Boeck.)
Cheirurus strabo Web.
Toechomya beushauseni (Maur.)
Cypricardinia contexta Barr.

The decisive predominance in our fauna of endemic species, together with its property noted above—the striking abundance of individuals belonging to relatively few forms—enabled me, as early as 1935, on the basis of only a preliminary acquaintance with this fauna, to express the opinion that “this fauna lived under conditions of substantial isolation” (Khalfin, 1935, pp. 21, 32). I can now confirm the validity of this conclusion on the basis of a careful study of many groups of the Devonian fauna of Siberia; it can be illustrated especially clearly by comparing the leptaenodontelloid fauna with the fauna of the Zhyvetsian–Frasnian deposits of Altai, in which cosmopolitan forms predominate and the components of which are quantitatively developed much more evenly. In Chapter III the question of the character of the isolation that determines the composition of our fauna is considered specially.

The endemic character of the leptaenodontelloid fauna by no means signifies that it is not connected with the fauna of other regions and countries: alongside species having a wholly endemic character, there is present in it a considerable number of forms similar to, and in a number of cases undoubtedly related to, forms from other countries—not to mention those eight species that are identical with European and Asiatic fossils of the Lower Devonian. Thus, in the fauna of the Kondratyevo Formation there are local varieties of two European (Nuculoidea lodanensis and Pterinopecten niobe) and one American (Delthyris perlamellosa) species. In addition, this fauna contains a considerable number of forms vicariant with European and American ones; in Table 9 all forms of our fauna that are identical with or similar to previously described ones are brought together. This similarity, in different cases, undoubtedly has a different character. Thus, we may distinguish forms that show a similarity to one or another of the previously described species of a purely convergent character; for example, this is the only way to assess the similarity between the Kondratyevo ($D_1^2$) Mytilarca tenuis and Mytilarca attenuata from the upper part of $D_3$ (Chemung) of the state of New York: in this case the difference in the stratigraphic position of these forms is too great. Apparently, the similarity of some of our forms to Lower Devonian forms of South America must be evaluated in the same way, for example: our Lichas parva and Lichas ballivianus from $D_1$ of Bolivia; our Cleidophorus regularis and Cleidophorus sharpei from $D_1$ of Brazil. In this case, however, the possibility of closer genetic relationships is not excluded. There is yet another case of similarity that must be regarded as a case of convergence only: sometimes we have a group of closely related forms that evidently constitutes a local association, but some members of this group show similarity to various forms from different countries. For example, in the fauna of the Medvedevo Formation ($D_1^2$)

chonetes constitute a local group of forms closely related to one another, but some of the members of this group are morphologically similar to European chonetes; I am inclined to regard this as a case of convergence, which does not permit any conclusions to be drawn (apart from the conclusion about similar conditions of existence). In the fauna of the Kondrat’evo Formation a similar case may be indicated for the species Chonetes bistriata n. sp., which is undoubtedly close to the specifically local species Chonetes rectispina (and probably derived from the latter), but which morphologically in some respects is also very close to the North American form Chonetes jerseiensis Well. var. spinosa Mayn.

Alongside the examples cited above, we have numerous cases in which vicariant forms have, evidently, close genetic relationships that can be used for important stratigraphic and biogeographic conclusions. Thus, for example, Probolium altaicum, so widely distributed in our fauna, belongs to a very narrow taxonomic group of dalmanitids (9 species), which also has a very narrow vertical distribution (1 species—\(S_2\), the others—\(D_1\)); it shows an undoubted kinship with the other members of this group, especially with the Canadian Probolium bidardi Clarke (Fig. 8). In the present case, the presence of representatives of the genus Probolium in Lower Devonian deposits of different countries of the northern hemisphere is evidently the result of their dispersal through a system of interconnected basins. The genetic connection of our Archaeocardium scrobiculare with the Bohemian representatives of this genus is still more evident; this is a very close association of forms that quite evidently had a single nearest common ancestor. Likewise, the clearly Bohemian type of most trilobites and gastropods, and the evident closeness of our pleurodictyids and pterineids (Tolmaia squamosa) to species of the Rhenish Devonian, indicate a connection of the Altai basin, inhabited by our fauna, with the European sea of the Lower Devonian; in the course of migrations (possibly reciprocal) the organisms evolved, which is why in Europe and in Altai we find in most cases only vicariant, not identical, forms, but at the same time they nevertheless prove to be very close in many respects, preserving a number of common features; thus we may say that in the fauna of the Kondrat’evo Formation we have a number of local forms genetically vicariant with European and American species, alongside certain purely endemic groups (Leptodontella, Wilsoniella, Myalinopterella, etc.). These latter indicate a certain isolation of our fauna. There are also other indications of this same isolation, though negative in character, yet no less important: the complete or almost complete absence of certain generic groups that are very widely developed in the Lower Devonian faunas of other regions and countries. Thus, for example, in our fauna of pelecypods representatives of the genera Leptodesma Hall and Leiopteria Hall, so widely distributed in the European Eodevonian, are entirely absent. The genera Modiomorpha Hall and Grammysia Vern., very diverse and numerous in the Lower Devonian fauna of Europe, occur in our fauna extremely rarely.

Fig. 8. Cephalons of Probolium altaicum Khalf. (a) and Probolium bidardi Clarke (b); schematic.

Excluding from the calculations those forms that cannot serve for the purposes of characterizing the geographic type of the fauna (i.e., forms determined only to genus, or forms whose relationship to morphologically similar species of other countries remains unclear), we obtain the following breakdown of all the remaining components of our fauna by geographic groups¹:

Table 8

Geographic groups	identical	close	total
of the European type (Eu)	5	26	31 (40%)
of the Asiatic type (As.)	1	—	1 (1.3%)
of the American type (Am)	—	4	4 (5.7%)
of the endemic type (En)	—	—	41 (53%)

The following remarks must be made concerning these figures: 1) the predominance of endemic forms in the fauna of the Kondrat’evo Formation, apparent from the percentage content given above of representatives of the various geographic groups, becomes still more evident if one takes into account that, of the 31 forms of the European type, 26 are new species or local varieties. 2) In this endemic fauna a strong European influence is evident; by contrast, the connection with the American fauna proves to be very weakened in comparison, for example, with the fauna of the Gani Formation (see above). It must, however, be noted that, of the four forms of the American type, Probolium altaicum, Phacops substriata, and Leiopecten rectangularis have a mass development in the fauna of the Kondrat’evo Formation and in this sense constitute a very conspicuous element of it; it may even be said that, in number of individuals among the trilobites of our fauna, the American elements predominate. 3) Only one species—Cheirurus strabo, absent from the European fauna—has been placed in the geographic group of forms of the Asiatic type; however, a number of forms of the latter are also known in the fauna of the Asiatic Devonian, for example: Chonetes sarcinulata, Delthyris carinthiaca, Cyrtina heteroclita, Calymene blumenbachii, Crotalocephalus sternbergi; all these species are counted in our table only in the group of forms of the European type.

Summing up everything said above, we may define the geographic type of the fauna of the Kondrat’evo Formation as follows: it is essentially an endemic fauna, representing the population of a special zoogeographic unit; this fauna shows a noticeable influence upon it of the fauna of the European-Asiatic seas and is connected to a considerably lesser degree with the fauna of North America.

The facies type of our fauna and the facies analogues of the Kondrat’evo Formation in Europe are established without difficulty; in this respect the joint presence in the fauna of the Kondrat’evo Formation of typical representatives of the Bohemian and Rhenish faunas of the Lower Devonian is characteristic.

To the fauna of the Bohemian type belong: among the brachiopods—Leptaena bouei and delthyrids; among the trilobites—representatives of the genera Bronteus, Lichas, Acidaspis, Crotalocephalus; among the mollusks—Pterinopecten niobe Barr. var. altaica, Plethomytilus pseudoconspicuus, and especially—Archaeocardium scrobiculare and gastropods. No less significant is the composition of the group of forms of the Rhenish facies type; here should be assigned, first of all, the pleurodictyums, pterineids (Tolmaia squamosa) and Atrypa lorana, which are abundant in our fauna; here also belong such forms,

Table 9

Comparison of the faunal components of the Kondrat’evo Formation with closely related forms

Kondrat’evo Formation	Europe and Asia	America
1. Chonetes bistriata n. sp.		[Chonetes jerseyensis Well.] Gedinnian deposits of the USA (Keyser limestone and its analogues).
2. Chonetes cf. sarcinulata Schl.	Chonetes sarcinulata Schl. \(D_1—D_2\) of Europe and Asia.
3. Leptaena bouei Barr.	Leptaena bouei Barr. Zlichovian deposits of Czechoslovakia (Koněprusy limestone); Lower Coblenzian deposits of Brittany (shales with Athyris undata) and the Rhenish Mountains (Grauwacke of Erbsloch); \(D_1\) Bosphorus.
4. Stropheodonta sedgwicki (Vern. et Arch.)	Stropheodonta sedgwicki Vern. et Arch. Lower Coblenzian deposits of the Westerwald, \(D_1\) Belgium; \(D_1^3\) Western Pyrenees; \(D_1\) Dobruja (?).
5. Isorthis cf. trigeri (Vern.)	Isorthis trigeri Vern. Lower Coblenzian deposits of the Rhenish Slate Mountains (Grauwacke of Erbsloch and Marburg); \(D_1\) Brittany; \(D_1\) Bosphorus.
6. Delthyris cf. koegeleri (Scup.)	Delthyris koegeleri (Scup.) \(D_1\) of the Carnic Alps (“reef limestones”).
7. Delthyris cf. carinthiaca (Frech)	Delthyris carinthiaca (Frech) \(D_1—D_2\) of the Carnic Alps; \(D_1^2\) Turkestan (?).
8. Delthyris cf. robusta (Barr.)	Delthyris robusta (Barr.) Zlichovian deposits of Czechoslovakia (Koněprusy limestone); Upper Coblenzian deposits of Brittany (Erbré limestone); \(D_1\) of the eastern slope of the Urals (?).
9. Delthyris perlamellosa (Hall) var. altaica Khal.		Delthyris perlamellosa (Hall). Zlichovian deposits of the USA (Helderberg stage, New Scotland horizon).
10. Cyrtina heteroclita (Defr.)	Cyrtina heteroclita Defr. \(D_1—D_3\) of Europe and Asia.
11. Atrypa lorana Fuchs	Atrypa lorana Fuchs. Lower Coblenzian and Zlichovian deposits of the Rhenish Slate Mountains; \(D_1\) Belgium and the Western Pyrenees; the Calcaire de Grison of northern France.
12. Bronteus cf. angusticeps Barr.	Bronteus angusticeps Barr. Zlichovian deposits of Czechoslovakia (Koněprusy limestone).
13. Bronteus altaicus n. sp.	[Bronteus granulatus Goldf.] \(D\) of the Garonne and the Urals.
14. Bronteus regularis n. sp.	Bronteus richteri Barr. Upper Eodevonian or lower Mesodevonian of Czechoslovakia (Luzetz limestone).
15. Cyphaspis (?) pulchella n. sp.	[“Proetus” lusor Barr.] Zlichovian deposits of Czechoslovakia (Koněprusy limestone).	[Proetus pachydermatius Barrett.] Gedinnian deposits of the USA (Keyser limestone and its equivalents).
16. Lichas (Euarges) parva n. sp.	Lichas hauri Barr. \(D_1—D_2\) Czechoslovakia.	[Lichas ballivianus Kozl.] \(D_1\) Bolivia.
17. Acidaspis (Leonaspis) punctata n. sp.	Acidaspis pigra Barr. Lower Devonian of Czechoslovakia. Acidaspis propinqua Barr. Upper Silurian of Czechoslovakia.
18. Calymene ex gr. C. blumenbachii Brogn.	Calymene blumenbachii Brogn. Europe. Upper Silurian.
19. Crotalocephalus sternbergi (Boeck.)	Crotalocephalus sternbergi (Boeck.) \(D_1\) and \(D_2\) of Czechoslovakia; \(D^2_1\) of the Carnic Alps; \(D_2\) of England; \(D_3\) and the Cultrijugatus beds of France; \(D^1_2\) Turkestan.
20. Cheirurus strabo Weber.	Cheirurus strabo Web. Lower Devonian of Ferghana.
21. Probolium altaicum (Khalf.)		Probolium biardi Clarke. Upper half of the Eodevonian (Oriskany stage) of North America (Grande Grève limestone of the island of Gaspé).
22. Phacops subcristata n. sp.		Phacops cristata Hall, \(D_1\) and \(D_2\) USA; Phacops salteri Kozl. \(D_1\) Bolivia.
23. Pterinopecten niobe (Barr.) var. altaica Khalf.	Pterinopecten niobe (Barr.). Zlichovian deposits of Czechoslovakia (Koněprusy limestone).
24. Leiopecten rectangularis Khalf.		Leiopecten umbonatus Conr. Zlichovian deposits of the USA (Coeymans horizon of the Helderberg stage).
25. Tolmaia squamosa Khalf.	Tolmaia lorana (Fuchs). Lower Coblenzian stage of the Rhenish Slate Mountains.
26. Mytilarca tenuis Khalf.	“Mytilus” elongatus Barr. “Mytilus” raptus Barr. Zlichovian deposits of Czechoslovakia (Koněprusy limestone).	[Mytilarca attenuata Hall.] \(D_3\), State of New York.
27. Plethomytilus pseudocconspicuus Khalf.	“Mytilus” conspicuus Barr. Zlichovian deposits of Czechoslovakia (Koněprusy limestone).
28. Nuculoidea lodanensis Beush. var. altaica Khalf.	Nuculoidea lodanensis Beush. Upper Coblenzian deposits of the Rhenish Slate Mountains and Devonian [[unclear: word]].
29. Tancrediopsis elegans Khalf.	Tancrediopsis subcontracta Beush. Upper Coblenzian deposits of the Rhenish Slate Mountains (Kieselgallenschiefer of Kellerwald).
30. Cleidophorus regularis Khalf.		Cleidophorus sharpei (Reed) \(D_1\) Brazil.
31. Toechomya subcircularis Khalf.	Toechomya circularis (Beush.) Lower- and Upper Coblenzian deposits of the Rhenish Slate Mountains.
32. Toechomya beushauseni (Maur.)	Toechomya beushauseni (Maur.). Upper Coblenzian deposits of the Rhenish Slate Mountains and the Harz.
33. Toechomya cf. intermedia (Dahm.)	Toechomya intermedia (Dahm.). Upper Coblenzian deposits of the Harz (sandstones of Kahleberg).
34. Praemyophoria latifrons Khalf.	Praemyophoria inflata (Roem.) mut. primaeva Kegel. Zlichovian deposits of the Rhenish Slate Mountains (Taunus quartzite).
35. Cypricardinia contexta Barr.	Cypricardinia contexta Barr. Zlichovian deposits of Czechoslovakia (Koněprusy limestone).
36. Paracyclas edentalis Khalf.	Paracyclas marginata Maur. Lower- and Upper Coblenzian deposits of the Rhenish Slate Mountains.
37. Archaeocardium scrobiculare Khalf.	Archaeocardium faustulum (Barr.). Upper Silurian of Czechoslovakia (Tachlovice limestone). Archaeocardium animans (Barr). \(D_1\) of Czechoslovakia, Koněprusy limestone.
38. Zygopleura n. sp., aff. Z. devonicans (Barr.).	Zygopleura devonicans (Barr.). Zlichovian deposits of Czechoslovakia (Koněprusy limestone).
39. Stylonema n. sp., aff. S. solvens (Barr.).	Stylonema solvens (Barr). Gedinnian deposit of Czechoslovakia (Kosor).
40. Cyclonema n. sp., aff. C. guilleri Ohel.	Cyclonema guilleri Ohel. Upper Coblenzian deposits of Brittany (Erbré).
41. Turbocheilus n. sp., aff. T. immaturus (Barr.).	Turbocheilus immaturus (Barr.). Upper Silurian deposits of Czechoslovakia (Dlouhá Hora, etc.).
42. Pleurodictyum cf. problematicum Goldf.	Pleurodictyum problematicum Goldf. Lower Devonian of Europe.

Note: names of identical forms are set in bold type; spaced type indicates forms represented in Altai by local varieties; forms only morphologically similar are placed in square brackets.

such as Stropheodonta sedgwicki, Nuculoidea lodanensis Beush. var., trigoniids, and some others. It may be considered that, in the fauna of the Kondrat’evka Formation, elements of the Bohemian and Rhenish types are distributed approximately equally. Deposits with a similar mixed Bohemian–Rhenish fauna are known in the Lower Devonian of the Rhenish Slate Mountains; they may be represented by the graywackes of Kellerwald (Erbsloch) and Marburg.

With regard to the age of the fauna of the Kondrat’evka Formation, the following may be said: there is no doubt that it belongs to the Lower Devonian, on the basis of the presence in it of the following forms:

Stropheodonta sedgwicki V. et A.
Leptaena bouei Barr.
Atrypa lorana Fuchs
Cheirurus strabo Web.
genus Probolium Oehl.
Cypricardinia contexta Barr.
Toechomya beushauseni (Maur.)
genus Archaeocardium Khalf.
genus Pleurodictyum Goldf.

Refining the age of our fauna within the Eodevonian already presents certain difficulties because of the predominance in it of local forms. Tables 10 and 11 summarize the stratigraphic indications of those components of the fauna of the Kondrat’evka Formation that might be significant in resolving this question. Considering these tables, we become convinced that it is difficult to decide the question of correlating the Kondrat’evka Formation with one of the stages of the European or American Eodevonian on the basis of analysis of the fauna of this formation alone. Indeed, of the eight forms that proved possible to identify with European and Asiatic species, only two have a vertical distribution limited to the scale of a stage, and their stratigraphic position is different:

Cypricardinia contexta—D₁¹
Toechomya beushauseni—D₁³

It is known that, in general, exact correlation cannot be substantiated by individual identical forms; in the present case such individual forms, moreover, indicate different stages (which is not surprising, taking into account the distances that separated the Altai Lower Devonian basin from the seas of Western Europe). To an even lesser degree, when resolving questions of exact correlation, can we rely on indications from non-identical, but only related, forms; the latter can give us only a general orientation in resolving such questions, which, however, may have substantial significance in combination with other circumstances. In our particular case we shall make use of this “general orientation” somewhat below; here we shall merely note that the distribution of related forms (see Tables 10 and 11) also is not the same for the different groups. In general it may be said that, in our fauna, the stratigraphic evidence of the brachiopods, trilobites, and partly gastropods speaks in favor of the lower half of the Eodevonian, whereas the pelecypods for the most part tend toward its upper half.

We may approach the question of the stratigraphic position of the Kondrat’evka Formation from another side—from the standpoint of considering the geological setting accompanying this formation within the northwestern part of the Altai, first of all from comparison of this formation

Table 10

Names of forms	$S_2$	Europe: Siegenian stage: Rhine	Europe: Siegenian stage: Czechoslovakia	Europe: Siegenian stage: Carnic Alps	Europe: Lower Coblenzian stage	Europe: Upper Coblenzian stage	North America: Helderbergian stage: Coeymans beds	North America: Helderbergian stage: New Scotland beds	North America: Oriskany stage	$D_1$	$D_2$
Chonetes cf. sarcinulata	—	—	—	—	—	—	—	—	—	✕	✕
Leptaena bouei Barr.	—	⊕	⊕	—	⊕	—	—	—	—	—	—
Stropheodonta sedgwicki V. A.	—	⊕	—	—	—	—	—	—	—	⊕	—
Isorthis cf. trigeri (Vern.)	—	✕	—	—	—	—	—	—	—	✕	—
Delthyris cf. koegeleri (Scup.)	—	—	—	✕	—	—	—	—	—	—	—
Delthyris cf. carinthiaca (Frech.)	—	—	—	✕	—	—	—	—	—	—	—
Delthyris cf. robusta (Barr.)	—	—	✕	—	—	✕	—	—	—	✕	—
Delthyris perlamellosa Hall var. altaica	—	—	—	—	—	—	—	+	—	—	—
Cyrtina heteroclita Defr.	—	—	—	—	—	—	—	—	—	⊕	⊕
Atrypa lorana Fuchs	—	⊕	—	—	⊕	⊕	—	—	—	—	—
Bronteus cf. angusticeps Barr.	—	—	✕	—	—	—	—	—	—	—	—
Lichas parva n. sp.	—	—	—	—	—	—	—	—	—	✕	✕
Acidaspis punctata n. sp.	✕	—	✕	—	—	—	—	—	—	✕	—
Calymene sp.	✕	—	—	—	—	—	—	—	—	—	—
Crotalocephalus sternbergi (Boeck.)	—	—	—	—	—	—	—	—	—	⊕	⊕
Cheirurus strabo Web.	—	—	—	—	—	—	—	—	—	⊕	—
Phobolium altaicum Khalf.	—	—	—	—	—	—	—	—	—	✕	—
Phacops subcristata n. sp.	—	—	—	—	—	—	—	—	—	✕	✕
Pterinopecten niobe (Barr.) var. altaica	—	—	+	—	—	—	—	—	—	—	—
Leiopteria rectangularis Khalf.	—	—	—	—	—	—	✕	—	—	—	—
Tolmaia squamosa Khalf.	—	✕	—	—	—	—	—	—	—	—	—
Plethomytilus pseudoconspicuus Khalf.	—	—	✕	—	—	—	—	—	—	—	—
Nuculoidea lodanensis Beush. var. altaica	—	—	—	—	—	+	—	—	—	—	—
Tancrediopsis elegans Khalf.	—	—	—	—	—	✕	—	—	—	—	—
Toechomya subcircularis Khalf.	—	—	—	—	✕	✕	—	—	—	—	—
Toech. beushauseni (Maur.)	—	—	—	—	—	⊕	—	—	—	—	—
Toech. cf. intermedia (Dahm.)	—	—	—	—	—	✕	—	—	—	—	—
Praemyophoria latifrons Khalf.	—	✕	—	—	—	—	—	—	—	—	—
Cypricardinia contexta Barr.	—	—	⊕	—	—	—	—	—	—	—	—
Paracyclas edentalis Khalf.	—	—	—	—	✕	✕	—	—	—	—	—
Archaeocardium scrobiculare Khalf.	✕	—	✕	—	—	—	—	—	—	—	—
Zygopleura aff. devonicans (Barr.)	—	—	✕	—	—	—	—	—	—	—	—
Stylonema aff. solvens (Barr.)	—	—	✕	—	—	—	—	—	—	—	—
Cyclonema aff. guilleri Oehl.	—	—	—	—	—	✕	—	—	—	—	—
Turbocheilus aff. immaturus (Barr.)	✕	—	—	—	—	+	—	—	—	—	—
Pleurodictyum cf. problematicum Goldf.	—	—	—	—	—	—	—	—	—	✕	—

Symbols for Table 10: ⊕ presence of a form identical with an Altaian one;
+ presence of a species represented in the Altaian fauna by a local variety;
✳ presence of a closely related form.

Table 11

Names of forms	S₂	D₁¹	D₁²	D₁³	D₂¹	D₂²
Chonetes cf. sarcinulata Schl.		- - -	- - -	- - -	- - -	- - -
Leptaena bouei (Barr.)		—	—
Stropheodonta sedgwicki (V.A.)		—	—	—
Isorthis cf. trigeri (Vern.)		- - -	- - -	- - -
Delthyris cf. koegeleri (Scup.)		- - -
„ cf. carinthiaca (Frech.)		- - -
„ cf. robusta (Barr.)		- - -	- - -	- - -
„ perlamellosa (Hall.) var.		- - -
Cyrtina heteroclita (Defr.)		—	—	—	—	—
Atrypa lorana Fuchs.		—	—	—
Bronteus cf. angusticeps Barr.		- - -
Lichas parva n. sp.		- - -	- - -	- - -	- - -	- - -
Acidaspis punctata n. sp.	- - -	- - -
Calymene sp.	- - -	- - -	- - -	- - -
Crotalocephalus sternbergi (Boeck.)		—	—	—	—	—
Cheirurus strabo Web.		—	—	—
Probolium altaicum Khalf.		- - -	- - -	- - -
Phacops subcristata n. sp.		- - -	- - -	- - -	- - -
Pterinopecten niobe (Barr.)		- - -
Leiopecten rectangularis Khalf.		- - -
Tolmaia squamosa Khalf.		- - -
Plethomytilus pseudoconspicuus Khalf.		- - -
Nuculoidea lodanensis Beush. var.				- - -
Tancrediopsis elegans Khalf.				- - -
Toechomya subcircularis Khalf.			- - -	- - -
„ beushauseni (Maur.)				—
„ cf. intermedia (Dahm.)				- - -
Praemyophoria latifrons Kalf.		- - -
Cypricardinia contexta Barr.		—
Paracyclas edentalis Khalf.			- - -	- - -
Archacocardium scrobiculare Khalf.	- - -	- - -
Zygopleura aff. devonicans (Barr.)		- - -
Stylonema aff. solvens Barr.		- - -
Cyclonema aff. guilleri Ohel.				- - -
Turbocheilus aff. immaturus (Barr.)	- - -
Pleurodictyum sp.		- - -	- - -	- - -

Symbols: — distribution of identical forms;
······ distribution of species represented in the Altaian fauna by local varieties;
- - - distribution of closely related forms.

with the other Lower Devonian formations studied by us. The relations between the Ganino and Kondrat’evo formations are determined by the following data, obtained as a result of field observations and a detailed study of the fauna of both formations.

1. In the fauna of both formations there are only five common forms:

Leptaena bouei,
Cyrtina heteroclita,
Leptodontella rotundata,
Atrypa lorana,
Leiopecten rectangularis.

In all other respects the fauna of the formations being compared is different.

1. These differences cannot be explained by facies causes, since in this respect the Ganino formation¹ is entirely similar to the Kondrat’evo formation.

¹ This refers to its pseudotogatov horizon.

1. These differences in the composition of the fauna cannot be explained by the development, in each of the formations, of forms local in relation to the fauna of the other formation: the deposits being compared were formed in immediate proximity to one another.

2. The most natural assumption remains that the differences in the fauna of the formations being compared are explained by differences in their stratigraphic position.

3. This assumption is supported by geological data: the Ganin Formation represents deposits of a complete sedimentation cycle, which ended with the formation of lagoonal sediments—that is, with shallowing and, probably, desiccation of the basin. The Kondrat’evka Formation has a basal conglomerate at its base. All this, in connection with the preceding point, indicates the presence of a denudational break between these formations, i.e., their different age.

4. In this respect, the stratigraphic indications of the various members of the fauna of the Kondrat’evka Formation, which are summarized in the tables, also acquire considerable value, since they quite clearly point to the appearance in the fauna of the Kondrat’evka Formation of rather numerous Koblenzian elements that are entirely absent from the fauna of the Ganin Formation.

On the basis of the material set out above, we arrive at the conclusion that the Kondrat’evka Formation is younger than the Ganin Formation. If we recall that, with respect to the latter, its Siegenian age has been precisely established, then, taking into account the composition of the fauna of the Kondrat’evka Formation, we may, with a considerable degree of probability, regard it as corresponding to the Lower Koblenzian stage of the European Eodevonian. By an analogous comparison of the Kondrat’evka and Medvedevka formations (see below, p. 69), it has been established that the latter is younger.

Thus, we come to the conclusion: the Kondrat’evka Formation is younger than the Ganin Formation and is separated from the latter by an interruption in sedimentation; the most probable correlation is that of the Kondrat’evka Formation with the Lower Koblenzian stage of the European division $D_1$.

The standard section of the Kondrat’evka Formation is the section present on the southern slope of Kondrat’evka Hill—the right side of the Peschanaya River, three kilometers south of the village of Kuyagan.

3. Medvedevka Formation

In 1930, I. P. Komarov delivered to the West Siberian Geological Administration samples of marly sandstones with a distinctive fauna, collected by him in the channel of the Bol’shaya Tikhaya River, above the village of Aleksandrovka, in the northwestern part of Altai (see Fig. 4). While working in the summer of 1930 in the Kuyagan district, one of my tasks was to establish the original locality of the formation containing this fauna and to study it. This formation was discovered by me on the southern slope of the Cherny Range (Fig. 4); its best section is in Medvedev Log, which enters the Bol’shaya Tikhaya River from the right, above the village of Aleksandrovka. In 1935 I gave a brief characterization of these deposits and their fauna, establishing their Koblenzian age; I called these deposits the “Medvedev Log sequence.” Now, when the stratigraphy of the Lower Devonian of Altai has been worked out in detail, and the stratigraphic relationships of the formations composing it have been clarified, and the independent position of the Medvedev Log sequence in the stratigraphic scheme of Altai has been established, I consider it more convenient to call it the Medvedevka Formation.

Thus, the deposits of the Medvedevka Formation are developed along the southern slope of the Cherny Range, north of the village of Aleksandrovka; here they represent

constitutes a fairly thick monoclinal sequence, having a WNW strike and dipping steeply to the south. The lower stratigraphic part of the formation (the northern part on the map) is best exposed; its higher horizons to the south pass first beneath the deluvial deposits of the northern slope of the Chernyi Range, and then beneath the alluvium of the valley of the Bolshaya Tikhaya River (Fig. 9). South of this valley, along its left side, there is developed a limestone–phyllite sequence of the Upper Silurian, thrust, as will be shown below, from the south over the Medvedevka formation; but in places, from beneath the thrust surface, normal sedimentary rocks emerge, partly quite similar to the rocks of the Medvedevka formation developed north of the valley of the B. Tikhaya River. I am inclined to regard them as the upper horizons of this formation; thus, the valley of the B. Tikhaya River near the village of Aleksandrovka passes through deposits of the Medvedevka formation, a considerable part of which is concealed from observation by the alluvial deposits of this valley (Fig. 9). With this interpretation of the field observations, the thickness of the Medvedevka formation is determined at approximately 2500 m; but (as indicated above) only the lower part of the formation, about 750 m thick, is well exposed along the right tributaries of the B. Tikhaya River. Below is a description of the sequence of rocks composing the lower part of the formation.

“The most complete section of this part of the formation is present along the right side of Medvedev Log, which cuts this sequence of rocks across the strike and flows into the B. Tikhaya River at the eastern end of the village of Aleksandrovka. Along this log, for a distance of 850 m, numerous exposures are scattered; they are especially abundant in the upper half of the log, where they form a whole series of ridges of rock-like character, these ridges being separated by narrow turf-covered intervals. In the lower part of the log there are only isolated outcrops of Devonian rocks, since the latter here are covered by the deluvial mantle of the southern slope of the watershed of the Tikhaya and Kuyagan rivers (Chernyi Range).

This entire sequence is composed almost exclusively of terrigenous rocks, calcareous to varying degrees. The strike of these rocks is west-northwesterly, varying within 290–305°. The dip is to the SSW at an angle of 70–80°…

The lowest horizons of this sequence consist of alternating beds of argillaceous shales and sandstones of varying grain size. These rocks have bluish-greenish-gray colors and are calcareous to varying degrees; on weathering they become brown and porous. In some beds the calcareous material predominates over the clastic material, and the rocks pass into argillaceous and sandy limestones. In all exposures of this part of the sequence, sandstones predominate, while the turf-covered intervals are apparently composed of argillaceous shales” (Khalfin, 1935, p. 13).

Fig. 9. Schematic section of the Medvedevka formation near the village of Aleksandrovka. M — Medvedevka formation; M₁ — lower phyllitic part of the Medvedevka formation; K — effusives of the Kuyagan–Okharakterizovannaya formation.

Higher stratigraphically (lower down the slope), greenish-gray, more rarely bluish-gray argillaceous shales predominate, also effervescing with HCl; calcareous sandstones of the same colors occupy a subordinate position here.

Benthos-derived limestones in the formation described are very rare. In the section along Medvedev Log, such a limestone was found at only one point; it occurs in the middle part of the formation ... and is a dark-gray massive coral limestone (Favositiidae, Heliolitidae, Stromatoporidae); its thickness is about half a meter. Farther west, on the watershed between Medvedev and Tatarskii logs, ... two thin (10–12 cm thick) beds of rock were encountered that represent a peculiar conglomerate: small fragments of branching colonies of coelenterates and bryozoans are cemented by greenish-gray clastic material, quite similar to that which composes the rocks of the Medvedev Log formation.

At the base of the formation described lies a basal conglomerate, exposed ... at the summit of Mordovskii Log. The outcrops of this conglomerate can be traced for 40 m across the strike of the formation. The pebbles of the conglomerate consist chiefly of dark-gray coral limestone (Favositiidae, Amplexus sp. and others); the fauna from this conglomerate has not been studied, and it can only be said of it that it is entirely different from the fauna of the coelenterates from the Medvedev Log formation. The sizes of the pebbles are very varied—from small pebbles to blocks 30–40 cm in diameter. Less commonly, the pebbles in this conglomerate consist of black-gray, dense, slightly limy and greenish-gray sandstone, similar to the sandstones of the Medvedev Log formation. The green cement of the conglomerate, when it (the cement) consists of fine-grained material, closely resembles the rocks of Medvedev Log and also effervesces with HCl. But usually it has the character of an interfragmental breccia and is differentiated grus of the effusives of the Kuyagan Formation that underlie the formation described (Khalfin, ibidem).

As already indicated above, the higher horizons of the Medvedev Formation, distributed south of the B. Tikhaya River, are exposed extremely poorly, and there is no more or less complete section of them. At a considerable distance from the channel of the B. Tikhaya River, the left slope of its valley has no outcrops, and only approximately one kilometer from the channel of this stream does the steepness of the left side increase sharply and large, often rocky outcrops begin of the limestone-phyllite formation, composed of strongly metamorphosed rocks of the Upper Silurian. However, locally ... lower (down the slope) than the rocks of this formation there are small exposures of sedimentary rocks which, like the rocks of Medvedev Log, show no significant metamorphism. Among these rocks there are shales, macroscopically almost indistinguishable from the shales of Medvedev Log (only somewhat lighter), and brownish-gray and greenish-gray massive and dense limestones; such limestones are absent north of the Tikhaya River. Fauna has not been found in these rocks; their strike is about 325°, dip to the southwest at an angle of 60°–70°. In their general appearance and degree of metamorphism these rocks differ sharply from the Upper Silurian limestone-phyllite formation developed to the south. (Khalfin, ibidem). As already noted, I am inclined to regard the rocks just characterized as the highest horizons of the Medvedev Formation.

The lower boundary of this formation, as indicated above, is characterized by a basal conglomerate; the upper boundary is tectonic: the rocks of the limestone-phyllite formation \((S_2)\) have been thrust or overthrust from the south onto the Medvedev Formation.

A few words about the limestone-phyllite formation itself. The rocks of this formation bound on the south the complex of formations of the right bank of the B. Tikhaya River—the Kuyagan, Medvedev, and Malafeev formations (Fig. 4). The limestone-phyllite formation is composed of marbled fine-grained snow-white massive limestone and finely laminated green phyllites and chlorite schists. The rocks of this formation have predominantly a west-northwest strike and dip to the southwest at angles from 45° to 60°.

Along the northern boundary of this formation, at a number of points, one may observe phenomena accompanying the thrust (or overthrust) of the Silurian formation onto the rocks developed north of it. Thus, in a large outcrop south of the village of Aleksandrovka, composed for several tens of meters of alternating white limestones and phyllites, there are two zones in which these rocks display intense folding. Limestone with thin interbeds of green chloritic matter (chloritized material of clayey interlayers) forms in these zones series of folds of very different dimensions: their amplitude ranges from a few centimeters to one meter. The phyllites in these zones are extremely finely fissile, and pieces of white limestone of various sizes are pressed and ground into them.

The front of this thrust has been traced for 15 km.

Thus, the rocks of the Medvedev Formation in the north lie transgressively on the effusive-sedimentary formation¹, while from the south the rocks of the Upper Silurian limestone-phyllite formation have been thrust over them (Khalfin, ibidem).

Fauna in the Medvedev Formation is distributed only in its lower part: the first faunistic bed was encountered 200 m from the base of the formation, and farther on, over a distance of 250 m, there are 17 faunistic horizons, after which the fauna disappears completely, and in more

in the upper parts of the formation no organic remains have been found. The thicknesses of the fauna-bearing beds and the distances between them are shown to scale in Fig. 10; the faunal beds (outcrops) are numbered

Fig. 10. Vertical distribution of the fauna in the Medvedev Formation. Roman numerals are the numbers of the outcrops; Arabic numerals are distances along the normal from the footwall of the formation; check marks are effusives of the Kurgan Formation.

from bottom to top from I to XVII. The fauna in them occurs in enormous quantities, although it is not diverse; in places one can observe large

outcrops of bedding surfaces, entirely speckled with impressions of isolated brachiopod valves and some pelecypods. In composition this is a typical leptodontellid fauna, somewhat impoverished in comparison with the fauna of the Kondrat’evo Formation.

The presence in the section along Medvedev Log of a large number of outcrops that make it possible to trace the fauna through a whole series of successive horizons and beds makes it possible to draw certain conclusions about the conditions of existence of the leptodontellid fauna and brings out especially clearly some of its features. First of all, this concerns the uneven quantitative development of the components of the fauna: of the list of forms given in Table 12, comprising 88 names, 14 species (16%) are represented in mass development, while 40 forms (i.e., almost half) were each found in a single specimen; the remaining 34 forms are also represented in our extensive collection usually by two or three specimens each. This unevenness in the quantitative development of forms is still more apparent when the composition of the fauna of individual beds is considered; the usual picture is as follows: within a given bed, on one or another bedding surface, an enormous number of impressions of shell valves of one or two species is observed, to which are added, usually as single specimens, examples of other forms. A bionomic analysis of the basin in which the rocks of the Medvedevo Formation were deposited is given below (p. 124).

The composition of the fauna of the Medvedevo Formation and the distribution of its components by horizons are presented in Table 12. The vertical distribution of the most important groups of this fauna is shown graphically in Fig. 10. To determine the geographic and facies type of the fauna and to establish its age, Tables 13, 14, 15, and 16 have been compiled. From these materials we may conclude that in this fauna, as in the fauna of the Kondrat’evo Formation, endemic elements predominate and a considerable influence of the European Eodevonian faunas is preserved. In our fauna there are four European forms:

Leptaena bouei
Cyrtina heteroclita
Praemyophoria elongata
Montanaria elliptica.

Two European species—Nuculoidea grandaeva and Praemyophoria elongata—are represented by local varieties; in addition, there is a series of forms, partly determined approximately and partly certainly belonging to new species, but having close analogues in the European fauna. American elements remain very few in number. The distribution by geographic groups of those components of our fauna which can give definite indications on this question is presented in Table 13.

Table 13

Geographic groups	Number of forms: identical	Number of forms: close	Number of forms: total
of European type (Eu)	4	19	23 (30%)
of American type (Am)	—	6	6 (8%)
of native type (En)	—	—	44 (58%)
of cosmopolitan type (Co)	—	3	3 (4%)

Table 12

No.	Names of forms
*1.	Chonetes pseudobohemica n. sp.
2.	Chenetes pseudoextensa n. sp.
*3.	Chonetes subextensa n. sp.
4.	Chonetes alata Khalif.
5.	Chonetes mucronata n. sp.
6.	Productella (?) sp.
7.	Leptaena bouei Barr.
*8.	Brachyprion nalivkini (Khalf.)
*9.	Brachyprion latus (Khalf.)
*10.	Leptodontella planuscula (Khalf.)
*11.	Leptodontella acuta n. sp.
12.	Leptodontella subquadrata n. sp.
13.	Leptodontella cf. rotundata n. sp.
14.	Leptodontella cf. magna n. sp.
15.	Schuchertella altaica Khalf. n. var. minor
16.	Levenea transversa n. sp.
*17.	Conchidium celsiseptosum n. sp.
18.	Conchidium trigonale n. sp.
19.	Camarotoechia sp.
*20.	Spirifer paucicostatus Khalf.
21.	Spirifer paucicostatus Khalf. var. mesoloba
*22.	Spirifer korovini Khalf.
23.	Spirifer rarus Khalf.
*24.	Spirifer pseudofallax Khalf.
25.	Spirifer semicirculus Khalf.
26.	Spirifer cf. assimilis Fuchs
27.	Spirifer cf. mischkei Erec h.
28.	Spirifer n. sp. cf. iheringi Kays.
29.	Cyrtina heteroclita (Defr.)
30.	Rensselaeria cf. robustella Fuchs.
31.	Rensselaeria pteriformis n. sp.
32.	Rensselaeria sp.
33.	Newberria subparallela n. sp.
34.	Newberria sp.
35.	Phacops subcristata n. sp.
36.	Phacops sp.
37.	Pseudaviculopecten limatus (Khalf.)
38.	Pseudaviculopecten altaicus n. sp.
39.	Pseudaviculopecten sp. cf. P. aviformis (Whidb.)
40.	Pseudaviculopecten pluma (Khalf.)
41.	Pseudaviculopecten directus n. sp.
42.	Pseudaviculopecten disparicostatus n. sp.
43.	Pseudaviculopecten sp.
44.	Lyriopecten prior Khalf.
45.	Actinopteria semicircula n. sp.
46.	Actinopteria acuta n. sp.
47.	Actinopteria sp.
48.	Pteronites tenuis Khalf.
49.	Pteronites trigonalis n. sp.
50.	Pteronites sinuata n. sp.
51.	Pteronitella subquadrata Khalf.
52.	Myalina (?) sp.
53.	Modiomorpha (?) subregularis Khalf.
54.	Modiomorpha altaica n. sp.
55.	Modiomorpha nanella n. sp.
56.	Mytilomorpha scalpellum (Khalf.)
57.	Nuculites faba Khalf.
58.	Lithodomus primigenius Khalf.
59.	Nuculoidea grandaeva (Goldf.) var. altaica Khalf.
60.	Leda claviformis Khalf.
61.	Leda exacta Khalf.
*62.	Ctenodonta unimoda Khalf.
63.	Tancrediopsis pulchella Khalf.
64.	Tancrediopsis terminalis n. sp.
65.	Cleidophorus sibiricus Khalf.
66.	Toechomya gutta (Dahm) var. altaica Khalf.
67.	Praemyophoria elongata (Beush)
68.	Praemyophoria elongata (Beush.) var. magna
69.	Glossites multicostatus n. sp.
70.	Glossites n. sp., cf. Gl. concentricus (Goldf.)
71.	Glossites elongatus n. sp.
72.	Glossites sp.
73.	Elyinella prima Khalf.
74.	Grammysia modica n. sp.
75.	Leptodomella sibirica Khalf.
76.	Cercomyopsis tenuis n. sp.
77.	Cypricardinia parallela n. sp.
78.	Cypricardinia cf. trigosa Barr.
79.	Cypricardinia cf. squamosa Barr.
80.	Sphenotus longus Khalf.
81.	Montanaria elliptica n. nom.
82.	Edmondia regularis Khalf.
*83.	Edmondia centralis Khalf.
84.	Edmondia quasicentralis n. sp.
*85.	Edmondia ovoides n. sp.
*86.	Edmondia propinqua n. sp.
87.	Edmondia parallelogramm Khalf.
88.	Edmondia nuculaeformis n. sp.

Number of forms encountered in the outcrop	I	II н	II в	III	IV	V	VI	VII	VIII	IX н	IX с	IX в	X н	X в	XI н	XI в	XII	XIII	XIV н	XIV с	XIV в	XV	XVI	XVII	Devonian
	3	7	4	2	7	3	15	—	14	15	20	9	18	15	9	10	7	7	16	20	15	9	4	1	9

Designations: ⊕ mass development; ╪ single specimen.

н — lower part of the outcrop;
с — middle part of the outcrop;
в — upper part of the outcrop.

Table 14

Names of forms	Western Europe and Asia	North and South America
1. Chonetes pseudobohemica n. sp.	Chonetes bohemica Barr. Koněprusy Limestone (D₁) of Bohemia.
2. Chonetes pseudoextensa n. sp.	[Eodevonaria extensa (Kays.)] Upper Coblenzian deposits of the Rhenish Slate Mountains.
3. Chonetes alata Khal f.	Chonetes bialata Fuchs. Lower Coblenzian deposits of the Rhenish Slate Mountains.
4. Leptaena bouei Barr.	Leptaena bouei Barr. Koněprusy Limestone (D₁) of Bohemia; bed with Athyris undata (D₁) of Brittany; Grauwacke of Erbsloch (D₁²) of the Rhenish Slate Mountains; D₁ of the Bosporus.
5. Brachyprion nalivkini (Khalf.)	Stropheodonta taeniolata Sandb. Lower Devonian of the Rhenish Slate Mountains; D₃ of the Western Pyrenees. Stropteodonta phillipsii (Barr.). S₂—D₁² of Czechoslovakia.	Stropheodonta patersoni Hall. D₁—D₁² of North America.
6. Brachyprion latus (Khalf.)		Brachyprion maja (Clarke). Oriskany stage of the USA.
7. Levenea transversa n. sp.	Schizophoria provulvaria (Maur.). Siegenian deposits (D₁) of Belgium and Germany; Upper Coblenzian deposits of the Western Pyrenees.
8. Spirifer paucicostatus Khalf. var. mesoloba	Spirifer cabanillus V. A. Lower Devonian of Asturias.
9. Spirifer korovini Khalf.		[Spirifer parana Clarke] D₁ of Brazil.
10. Spirifer pseudofallax Khalf.	[Spirifer psuedoviator Scup] D₁ of the Carnic Alps.
11. Spirifer cf. assimilis Fuchs	Spirifer assimilis Fuchs. Lower Devonian of the Rhenish Slate Mountains.
12. Spirifer cf. mischkei Frech	Spirifer mischkei. Lower Devonian of the Rhenish region.
13. Spirifer n. sp., cf. Sp. iheringi Kays.		[Spirifer iheringi Kays.] D₁ of South America.
14. Cyrtina heteroclita (Def.)	Cyrtina heteroclita (Def.) Devonian of Europe and Asia.
15. Rensselaeria cf. robustella Fuchs	Rensselaeria robustella Fuchs. D₁ of the Rhenish Slate Mountains.
16. Newberria subparallela n. sp.		Newberria johannis Hall. D₂ of North America.
17. Phacops subcristata n. sp.		{ Phacops cristata Hall. D₁ and D₂ of North America { Phacops salteri Kozl. D₁ of Bolivia
18. Actinopteria acuta Khalf.		Actinopteria insignis Clarke. Oriskany stage of the USA.
19. Pseudaviculopecten sp. cf. P. aviformis Whidb.	Pseudaviculopecten aviformis Whidb. D₂ of southern England.
20. Pteronitella subquadrata Khalf.		Pteronitella quadrata Will. et Bregg. Upper Helderbergian stage of the USA (Chapman sandstone, state of Maine).
21. Modiola faba Khalf.	Modiola lodanensis Beush. Upper Coblenzian deposits of the Harz (Kahleberg sandstone).
22. Mytilomorpha scalpellum (Khalf.)	Mytilomorpha peracuta (Drev.) Upper Coblenzian deposits of Germany.
23. Nuculoidea grandaeva (Goldf.) var. altaica Khalf.	Nuculoidea grandaeva (Goldf.) var. kahlebergensis Beush. Kahleberg sandstone (D₁³) of the Harz.
24. Leda claviformis Khalf.	Leda securiformis Goldf. D₁² and D₁³ of the Rhenish Slate Mountains.	Leda brevirostris Hall. D₂ of North America.
25. Ctenodonta unimoda Khalf.	{ Ctenodonta obovata Beush. { Ctenodonta elongata Beush. { Ctenodonta hercynica Beush. } Upper Coblenzian deposits of the Harz. Siegenian stage of the Rhine.
26. Cleidophorus sibiricus (Khalf.)	{ Cuculella cf. oblongata Conn. (Walther, 1903). Upper Coblenzian deposits of Nassau. { Cleidophorus ? intermedius (Beush.). Lower Coblenzian deposits of the Rhine.
27. Toechomya gutta Dahm. var. altaica Khalf.	Toechomya gutta Dahm. Upper Coblenzian stage of the Harz.
28. Praemyophoria elongata (Beush.)	Praemyophoria elongata (Beush.), Kahleberg sandstone (D₁³) of the Upper Harz.
29. Praemyophoria elongata (Beush.) var. magna Khalf.	Idem. Ibidem.
30. Elymella prima Khalf.		Elymella harisi Will. et Bregg. Upper Helderbergian stage of the USA (Chapman sandstone).
31. Leptodomella sibirica Khalf.	Leptodomella lata (Kranz). Middle Devonian of the Rhenish Slate Mountains.
32. Glossites sp., cf. G. concentricus Goldf.	Glossites concentricus Goldf. D₂ of the Rhenish Slate Mountains.
33. Cypricardinia cf. gratiosa Barr.	Cypricardinia gratiosa Barr. Koněprusy Limestone of Bohemia (D₁).
34. Cypricardinia cf. squamosa Barr.	Cypricardinia squamosa Barr. Koněprusy Limestone.
35. Sphenotus longus Khalf.	Sphenotus soleniformis Goldf. (pars). Siegenian stage (D₁) of the Rhenish Slate Mountains.
36. Montanaria elliptica Khalf.	Montanaria elliptica Khalf. (Syn. Montanaria elongata Spriest.—pars). Upper Coblenzian deposits of the Rhenish Slate Mountains (Emsian sandstone).
37. Edmondia regularis Khalf.		[Edmondia sylvana Hartt. et Rath.] D₁ of Brazil.

Note: bold type indicates identical forms; letter spacing indicates forms represented in the Altai by local varieties; forms in square brackets are only morphologically similar.

Table 15

Names of forms	Upper Silurian	D₁ Europe: Ziegenian stage—Izvestn. Koneprus	D₁ Europe: Ziegenian stage—D₁, Rhenish Slate Mtns.	D₁ Europe: Lower Coblenz stage	D₁ Europe: Upper Coblenz stage	D₁ North America: Helderbergian stage	D₁ North America: Oriskanian stage	D₁	D₂
Productella (?) sp.	—	—	—	—	—	—	—	—	*
Chonetes pseudobohemica n. sp.	—	*	—	—	—	—	—	—	—
Chonetes alata Khalf.	—	—	*	—	—	—	—	—	—
Leptaena bouei (Barr.)	—	⊕	⊕	⊕	—	—	—	—	—
Brachyprion nalivkini (Khalf.)	*	—	—	—	—	—	—	*	*
Brachyprion latus (Khalf.)	—	—	—	—	—	—	*	—	—
Levenea transversa n. sp.	—	—	*	?	*	—	—	—	—
Spirifer paucicostatus Khalf. var. mesoloba	—	—	—	—	—	—	—	*	—
Spirifer cf. assimilis Fuchs	—	—	—	—	—	—	—	*	—
Spirifer cf. mischkei Frech	—	—	—	—	—	—	—	*	—
Cyrtina heteroclita (Defr.)	—	—	—	—	—	—	—	⊕	⊕
Rensselaeria cf. robustella Fuchs	—	—	—	—	—	—	—	*	—
Newberria subparallela n. sp.	—	—	—	—	—	—	—	—	*
Phacops subcristata n. sp.	—	—	—	—	—	—	—	*	*
Pseudaviculopecten sp., cf. Ps. aviformis Whidb	—	—	—	—	—	—	—	—	*
Actinopteria acuta Khalf.	—	—	—	—	—	—	*	—	—
Pteronitella subquadrata Khalf.	—	—	—	—	—	*	—	—	—
Modiola faba Khalf.	—	—	—	—	*	—	—	—	—
Mytilomorpha scalpellum (Khalf.)	—	—	—	—	*	—	—	—	—
Nuculoidea grandaeva (Goldf.) var. altaica Khalf.	—	—	—	—	+	—	—	—	—
Leda claviformis Khalf.	—	—	—	*	*	—	—	—	*
Ctenodonta unimoda Khalf.	—	—	*	—	*	—	—	—	—
Cleidophorus sibiricus (Khalf.)	—	—	—	—	*	—	—	—	—
Toechomya gutta (Dahm.) var. altaica Khalf.	—	—	—	—	+	—	—	—	—
Praemyophoria elongata (Beush.)	—	—	—	—	⊕	—	—	—	—
Praemyophoria elongata (Beush.) var. magna Khalf.	—	—	—	—	+	—	—	—	—
Glossites n. sp., cf. Gl. concentricus (Goldf.)	—	—	—	—	—	—	—	—	*
Elymella prima Khalf.	—	—	—	—	—	*	—	—	—
Leptodomella sibirica Khalf.	—	—	—	—	—	—	—	—	*
Cypricardinia cf. gratiosa Barr.	—	*	—	—	—	—	—	—	—
Cypricardinia cf. squamosa Barr.	—	*	—	—	—	—	—	—	—
Sphenotus longus Khalf.	—	—	*	—	—	—	—	—	—
Montanaria elliptica Khalf.	—	—	—	—	⊕	—	—	—	—

Symbols: ⊕ presence of a form identical with the Altaian one;
+ presence of a species represented in the Altaian fauna by a local variety;
* presence of a related form.

The fauna under analysis differs noticeably from the fauna of the Kondratiev Formation in its facies character; this is established from consideration of the components of this fauna that have a European geographic type. Among the representatives of the fauna of the Kondratiev Formation that have a European character, elements of the Bohemian and Rhenish facies types are present in approximately equal measure (see p. 59), which is why, in facies terms, we compare the deposits of the Kondratiev Formation with European deposits of the Erbsloch greywacke type, characterized by a mixed Bohemian–Rhenish fauna. In the fauna of the Medvedev…

Table 16

Names of forms	S₂	D₁¹	D₁²	D₁³	D₂¹	D₂²
Productella (?) sp.					⋯	⋯
Chonetes pseudobohemica n. sp.		⋯
Chonetes alata Khalf.		⋯
Leptaena bouei (Barr.)		—	—
Brachyprion nalivkini (Khalf.)	⋯	⋯	⋯	⋯	⋯	⋯
Brachyprion latus (Khalf.)			⋯	⋯
Levenea transversa n. sp.		⋯	⋯	⋯
Spirifer paucicostatus Khalf. var. mesoloba		⋯	⋯	⋯
Spirifer cf. assimilis Fuchs.		⋯	⋯	⋯
Cyrtina heteroclita (Defr.)		—	—	—	—	—
Newberria subparallela n. sp.					⋯	⋯
Phacops subcristata n. sp.		⋯			⋯	⋯
Pseudaviculopecten sp., cf. Ps. aviformis (Whidb.)					⋯	⋯
Actinopteria acuta Khalf.			⋯	⋯
Pteronitella subquadrata Khalf.		⋯	⋯
Modiola faba Khalf.				⋯
Mytilomorpha scalpellum (Khalf.)				⋯
Nuculoidea grandaeva (Goldf.) var. altaica				⋯
Lada claviiformis Khalf.			⋯	⋯	⋯	⋯
Ctenodonta unimoda Khalf.		⋯	—	⋯
Cleidophorus sibiricus (Khalf.)				⋯
Tcechomya gutta (Dahm.) var. altaica Khalf.				⋯
Praemyophoria elongata (Beush.)				—
Praemyophoria elongata (Beush.) var. magna				—
Glossites n. sp., cf. Gl. concentricus (Goldf.)						⋯
Elymella prima Khalf.		⋯
Leptodomella sibirica Khalf.					⋯
Cypricardinia cf. gratiosa Barr.		⋯
Cypricardinia cf. squamosa Barr.		⋯
Sphenotus longus Khalf.		⋯
Montanaria elliptica Khalf.				—

Symbols: — distribution of identical forms; ⋯ distribution of species represented in the Altai fauna by local varieties; ⋯⋯ distribution of closely related forms.

formations among its components that have a European geographic character, the Bohemian elements occupy a subordinate position, constituting only 20% of the forms of this part of the fauna; the remaining 80% consist of forms having a distinctly expressed Rhenish facies type. If to this we add that among the deposits of the Medvedev Formation containing fauna, medium-grained sandstones predominate, whereas in the Kondrat’ev Formation chiefly finer-grained varieties are developed, we shall have every reason to confirm in full, on the basis of an analysis of more extensive material, the conclusion that we had already reached on this question: “the deposits of Medvedev Log and Kondrat’evskaya Sopka are facies-different; the fauna of these deposits, while remaining endemic in its main mass and representing a peculiar type of mixture of European, native, and American elements, in its facies nature (and partly also in composition) approaches the mixed Rhenish-Bohemian faunas of Europe; at the same time the fauna of the Kondrat’evskaya

is similar to the fauna of the Grauwacke of Erbsloh, while the fauna of Medvedev Log approaches the normal Rhenish type” (Khalfin, 1940, p. 284).

Determining the age of the fauna of the Medvedev Formation presents certain difficulties and may be based partly on a general analysis of the fauna and on individual, very few, guide forms, but chiefly on an analysis of the general geological setting characterizing deposits with a leptodontelloid fauna in the northwestern part of the Altai.

Of the four forms that proved possible to identify with European species, Cyrtina heteroclita is stratigraphically indifferent; the other three indicate a Lower Devonian age for the fauna:

Leptaena bouei is widely distributed in the Lower Devonian deposits of Western Europe, specifically in the Siegenian and Lower Coblenzian stages; I have found no indications in the literature of the presence of this species in Upper Coblenzian deposits. On the contrary, Praemyophoria elongata and Montanaria elliptica point precisely to this upper stage of the European Eodevonian. The same is the stratigraphic position of the species Toechomya gutta and Nuculoidea grandaeva, which are represented here by local varieties. All these indications are, of course, of definite value, but it should not be forgotten that the above-mentioned Upper Coblenzian forms are represented in our fauna by single specimens. As for the stratigraphic indications of forms that are only close to one or another European and American species (Table 16), each such indication taken separately cannot be significant; but if they are sufficiently consistent for many forms, we are obliged to take them into account. In the present case, all the close forms (with the exception of five) are developed in the Eodevonian, for the most part in its upper horizons; i.e., the general character of our fauna is essentially Lower Devonian; but five close forms are distributed in the Mesodevonian (see Table 15). In comparison with the fauna of the Kondrat’ev Formation, it can be emphasized with complete certainty that the difference of the fauna under analysis consists in the predominance of Upper Coblenzian elements over Lower Coblenzian and Siegenian ones, and in the appearance—though of single occurrences—of Middle Devonian elements. Thus, from a comparison of the faunas of these two formations we arrive at the conclusion that the Medvedev Formation must be regarded as younger. And if we have found it possible to correlate the Kondrat’ev Formation with the Lower Coblenzian stage of Western Europe, then the Medvedev Formation should be considered as corresponding to the Upper Coblenzian stage. We shall now test this conclusion by a more detailed comparison of the paleontological and geological data relating to the two formations being compared.

In the fauna of both these formations I have identified and described 185 forms; of these, only three are common to both formations: Leptaena bouei, Cyrtina heteroclita, and Phacops subcristata. In addition, in the fauna of the Kondrat’ev Formation one specimen is identified as Leptodontella cf.? acuta, while in the Medvedev Formation one specimen of Leptodontella cf.? rotundata has been found; at the same time the species Leptodontella acuta has a mass development in the fauna of the Medvedev Formation, and the species Leptodontella rotundata is equally widespread in the deposits of the Kondrat’ev Formation. All the remaining forms (180 in number) occur either only in the Medvedev or only in the Kondrat’ev Formation. Thus, in the species composition of the faunas being compared there is clearly a profound difference. This difference becomes still more pronounced when we begin to compare the generic composition of the faunas under consideration; if we focus our attention only on the most important generic groups, we shall see that in most cases the genera, in

in large numbers widespread in the fauna of one of the formations are absent from the fauna of the other, or else are represented in these faunas by different species (the exception is the already noted Leptaena bouei). A comparison of the generic composition of the faunas being compared is given in Table 17.

Table 17

Names of genera	Kondratyev Formation	Medvedev Formation	Notes
Chonetes	many	many	no common species
Leptaena	many	few	common species L. bouei
Brachyprion	many	many	no common forms
Leptodontella	many	many	no common forms
Conchidium	none	many
Wilsoniella	many	none
Atrypa	many	none
Spirifer	very few	many	no common forms
Probolium	many	none
Phacops	many	very few	common species Ph. subcristata
Leiopcten	many	none
Tolmaia	many	none
Mytilarca	many	none
Myalinopterella	many	none
Ctenodonta	none	many
Ctenodontella	many	none
Toechomya	many	very few	no common forms
Praemyophoria	many	very few	no common forms
Paracyclas	many	none
Archaeocardium	many	none
Edmondia	none	many
Pleurodictyum	many	none
Gastropods	many	none

The table given above shows how substantial the differences are in the composition of the fauna of the formations being compared. This question was already considered by me earlier (Khalfin, 1940). The new data show that we have no grounds for introducing any changes into the conclusions then obtained:

“With all these differences, the same general character of the fauna is preserved for both formations—a mixed Rhenish-Bohemian-American type, with an endemic species composition, an uneven quantitative development of forms, and an uneven spatial distribution of the fauna in the form of biocoenoses, simple in composition, that existed in parallel within a single basin. This similarity in the general character of the faunas being compared in no way diminishes the significance of those profound differences in their composition which were noted above and which require interpretation.

In my preliminary report on the Devonian fauna of the Altai (1935), I was inclined to explain these differences by the above-characterized uneven distribution of the fauna within the basin, i.e., to assume that these differences between the faunas of the two given sequences have the same significance as the differences between the biocoenoses of individual beds within each of the given sequences. On the basis of a detailed study of the most important groups of our fauna (brachiopods, trilobites, pelecypods), which made it possible to form a sufficiently clear idea of its composition, I can no longer consider this explanation sufficient: by summing the fauna of individual beds (biocoenoses) in one and the other sequence, we obtain two faunas, connected by the same general character and by very few forms, and profoundly different in composition.

Let us see to what extent these differences may be due to differences of a facies and stratigraphic order.

In facies terms, the deposits of Medvedev Log and Kondratyev Sopka, as was clarified above, are different; let us try to establish the scale of these differences. Let us take as the starting point the fauna of the Kondratyev Formation; the composition of this fauna, in particular the abundance of brachiopods, trilobites, and pelecypods of the families Pterinopectenidae, Pterineidae, Ambonychiidae, etc., undoubtedly indicates that the salinity of the water of the corresponding basin was normal or close to normal. The fauna of Medvedev Log contains in its composition

very few trilobites, but the mass development of brachiopods and of the same pterinopectinids, pteriniids, etc., compels us to acknowledge that the salinity of the basin in which the deposits of the Medvedevka Formation accumulated was also normal or close to normal. Considering the composition of the fauna of the formations being compared, we have every reason to assert that there was no appreciable difference in the composition of the water of the basins in which these sequences were formed.

Turning to the question of the depth of the basin in which the faunas of interest to us lived, we note that the composition of the rocks indicates a greater deep-water character of the deposits of Kondrat’evskaya Hill in comparison with the deposits of Medvedev Log. However, the deep-water character of the deposits of the Kondrat’evskaya Formation is also relative: the composition of the fauna—the mass development of brachiopods, lamellibranchs, Phacopidacea, an abundance of bryozoans and some tabulates—indicates that the depths of the Kondrat’evskaya Hill basin were insignificant—probably within a few tens of meters. Taking the overall composition of the fauna of each of the compared localities, we are convinced that, bathymetrically, these faunas cannot have been substantially different.

Nor do we have any grounds for supposing that, with respect to water temperature, the basins of Kondrat’evskaya Hill and Medvedev Log possessed any differences.

Thus, we come to the conclusion that the existing facies differences between the deposits of Medvedev Log and Kondrat’evskaya Hill are insufficient to explain the profound differences in the composition of the fauna of these deposits.

We arrive at an analogous conclusion also with respect to stratigraphic differences: the faunas being compared are not synchronous, but close in age; the stratigraphic interval separating them is, possibly, within the limits of one stage, at most within the limits of two adjacent stages of the Lower Devonian. It is therefore not possible to explain by the difference in the stratigraphic position of these faunas such differences in their composition as, for example, the almost complete absence in the fauna of Medvedev Log of trilobites, richly and diversely represented in the fauna of Kondrat’evskaya Hill, or the disappearance in the deposits of Medvedev Log of such generic groups of pelecypods as Tolmaia, Leiopeten, Mytilarca, Myalinopterella, Paracyclas, Ctencdontella, which in the deposits of Kondrat’evskaya Hill occur in mass quantities (the same may be said also with respect to brachiopods, gastropods, and tabulates).

Thus, the differences in the composition of the fauna of Medvedev Log and Kondrat’evskaya Hill cannot be satisfactorily explained by stratigraphic or facies differences in the corresponding deposits. Having reached this conclusion, we naturally arrive at the only possible inference: that the profound differences in the composition of the faunas being compared were caused by the presence of some obstacle that almost completely disrupted the connection between these faunas. Considering the question that interests us from this point of view, we must at once reject the idea that the connection between the faunas was disrupted in space, i.e., that this obstacle had the character of a certain barrier separating the population of two basins. Against such an assumption speaks, first, the asynchrony of the faunas being compared; second, the sequence of Medvedev Log and the sequence of Kondrat’evskaya Hill are located in immediate proximity (about 10 km) to one another, while the very plan and character of the tectonics of Northern Altai exclude the possibility of supposing that both these sequences, or one of them, are allochthonous and have undergone considerable horizontal displacement.

It remains, therefore, to consider the question of a possible break between the faunas being compared in time. In fact, with considerable proximity in stratigraphic position and with an almost coincident geographic position of the formations being compared, the almost complete absence of continuity between the faunas of these sequences is striking: only Leptaena bouei, Cyrtina heteroclita, Phacops subcristata, and varieties of Leptodontella planuscula directly link the fauna of the formations being compared. We find the explanation of this phenomenon in the relationships of the deposits under consideration to the underlying rocks.

Both formations have at their base basal conglomerates lying directly on effusives of the Kuyagan Formation; the conglomerate occurring at the base of the Medvedev Log sequence has a thickness of not less than 40 m; beneath it there are no rocks corresponding to the Kondrat’evskaya Formation; evidently, they were either eroded before the deposition of the rocks of Medvedev Log. Thus, before us there emerges a picture of a break in deposition: the interval between the epochs of formation of the sequences of Kondrat’evskaya Hill and Medvedev Log corresponds to a certain phase of tectogenesis, which caused the emergence of the basin that had been populated by the fauna of the Kondrat’evskaya Formation. This emergence of the basin was evidently accompanied by the death of the greater part of its population, although it is possible that part of the latter emigrated in a direction as yet unknown. When this short-lived uplift was replaced by a new subsidence, which led to the new appearance in Northern Altai of a marine basin, this latter proved to be inhabited by a fauna completely different in composition. This fauna is, thus, not a product of the development of the preceding one, but is composed of new immigrants that settled the basin of Medvedev Log. And only very few forms of the fauna of the Kondrat’evskaya Formation—for example, the local leptodontellas, phacopsids, and the European Leptaena bouei and Cyrtina heterolita, which had appeared earlier in Altai—again appear in the basins of Medvedev Log, having survived somewhere through the period of desiccation of the North Altai basin.

In this form I envisage the relationship between the fauna of the Kondrat’evskaya and Medvedevka formations (Khalfin, 1940, pp. 284–286).

The conclusions from the exposition given above are as follows: the facies and stratigraphic differences between the deposits of the Kondrat'evka and Medvedevo formations are insufficient to explain the profound differences in the fauna of these deposits; the younger fauna of Medvedev Log, in its bulk, shows no genetic connection with the fauna of Kondrat'evka Hill, i.e., it is not the product of the evolution of this latter fauna; this is explained by the fact that the formation of the strata of Kondrat'evka Hill and of Medvedev Log was separated by a temporary drying-up of the Lower Devonian basin of Northern Altai; the sea that returned to the limits of Northern Altai at the very end of the Lower Devonian was populated by an immigrant fauna, substantially different from the fauna of the Kondrat'evka Formation.

The type section of the Medvedevo Formation is the section along Medvedev Log, which flows into the Bol'shaya Tikhaya River from the right, opposite the eastern end of the village of Aleksandrovka (Fig. 4); the standards of the formation are: a) the section in the upper reaches of Mordovskii Log, which flows into the Bol'shaya Tikhaya River from the right, two kilometers above the mouth of Medvedev Log (the basal conglomerate of the Medvedevo Formation); b) exposures along the left side of the valley of the Bol'shaya Tikhaya River, south of the village of Aleksandrovka (the upper horizons of the Medvedevo Formation beneath the Upper Silurian thrust over them).

IV. Undivided Lower Devonian

The Lower Devonian deposits of the Anui–Kuyagan geosynclinal zone, belonging to five different formations and embracing the stratigraphic interval from the Gedinnian through the Upper Coblenzian stages inclusive, have been characterized in detail above. However, these formations do not exhaust the composition of the Eodevonian of the Anui–Kuyagan zone. In the literature there are a number of indications of the presence of Lower Devonian deposits at several localities which I did not visit and from which I had no fauna at my disposal. Unfortunately, the information on these deposits is very fragmentary:

“The Lower Devonian (probably also its upper part) has its greatest distribution in the northwestern part of Altai, where it is known along the Anui River (near the village of Soloneshnoye), along the Peschanaya River (near the village of Bulatovo), near the village of Baranchi, and at other localities. Lithologically the Lower Devonian is expressed by limestones, calcareous sandstones, and shales; the fauna is likewise varied in different places, in places trilobitic (...near Baranchi), in places coral (near Bulatovo).” (Nekhoroshev, 1932a, pp. 17–18).

This is how the Lower Devonian of the Anui–Kuyagan zone is characterized in the summary by V. P. Nekhoroshev; it is not difficult to see that from this characterization we can extract very little to supplement the materials given above on the Lower Devonian of the area under consideration. It can only be said that, in addition to the formations studied by us, there are also deposits at several localities, represented by various facies and assigned to the Lower Devonian. The latter, however, is not always obvious, since lists of forms are not given. Somewhat more detailed information is available only for the Devonian deposits in the vicinity of the village of Soloneshnoye. The section of these deposits along Pashennyi Creek (a tributary of the Chernyi Anui River), according to V. P. Nekhoroshev (1932, pp. 19–20, 82–83), is drawn in the following form: at the top lie greenish sandstones and shales with Atrypa reticularis L., Spirifer sp., Phacops sp.; downward they are replaced by calcareous-clayey shales, and then by black limestones with a coral fauna (Favosites, Pachypora, Stromatopora, Amplexus altaicus Dyb.). Lower down, green calcareous and clayey shales again appear, with Phacops sp., Pleurodictyum cf. problematicum Goldf., Atrypa sp., Semicoscinium sp., and finally, at the base of the succession, limestones with Favosites and Pachypora occur. “The total thickness of the section cited is considerable and, in any case, is measured in hundreds of meters” (p. 1).

The section cited could be of considerable interest in certain respects, if its fauna had been studied at least somewhat satisfactorily. Unfortunately, the determinations of the fauna given by V. P. Nekhoroshev are so approximate that the question of the age of the deposits of the Pashennyi spring cannot be regarded as finally established.

The key point in this question is Pleurodictyum cf. problematicum. Representatives of the genus Pleurodictyum occur in large numbers as part of the fauna of the Kondrat’ev Formation, which is of age \(D_1^2\). They have also been found in the Lower Devonian deposits of the Cherepanovskii mine and the village of Akimovskoe in Rudnyi Altai. Thus, the assignment of the lower part of the section cited to the Lower Devonian cannot be in doubt; but a refinement of this determination within the Lower Devonian can be made only on the basis of a detailed study of the entire fauna.

The environs of the village of Soloneshnoe were studied later by a number of geologists (B. F. Speranskii, M. K. Vinkman); unfortunately, none of them succeeded in collecting a satisfactory fauna from the deposits of interest to us. I had occasion to examine the fauna found by M. K. Vinkman, and could only say that it consists of indeterminable fragments of impressions of brachiopod and pelecypod shells; from the lithological character of the rocks on which these impressions were preserved, I could satisfy myself that among the deposits of the environs of the village of Soloneshnoe there are some which very much resemble the rocks of the Medvedev Formation. In various ways, the imperfect organic remains mentioned, enclosed in these rocks, could belong to certain forms from the leptontelloid fauna. But it is quite obvious that establishment of the exact stratigraphic position of the deposits of the village of Soloneshnoe is possible only on the basis of the study of a more successfully collected fauna.

Likewise, the deposits of the village of Baranchi with trilobites, mentioned above, and the coral limestones of the village of Bulatovo cannot be correlated with any of the formations established by us without preliminary study of the fauna.

V. Scheme of the Stratigraphy of the Eodevonian of the Anui–Kuyagan Geosynclinal Zone

The tectono-stratigraphic scheme of the West Siberian Territory compiled by M. A. Usov (1936) was worked out in its various parts with different degrees of detail; this is explained by the fact that, at the time this scheme was compiled, M. A. Usov had at his disposal materials characterizing the various stratigraphic intervals with differing degrees of detail. With regard to the Devonian system, it may be said that M. A. Usov’s scheme gives in great detail the subdivision of the Middle Devonian, within which four phases of tectogenesis are distinguished; by contrast, the Lower Devonian is subdivided very schematically: it is represented by two formations, the Krekov and the Pesterev, which are separated, according to M. A. Usov, by a break corresponding to the Nassau phase of tectogenesis of the Rhenish province. Such a “simple” composition of the Lower Devonian in comparison with the Middle is, of course, explained not by the natural properties of the former, but by the fact that the stratigraphy of the Eodevonian of the Sayan–Altai region until recently had been studied quite inadequately; M. A. Usov had only data on the stratigraphy of \(D_1\) of the margins of the Kuzbass, which to a number of authors still appears very “simple” for the very reason indicated above—because of the poor degree of study of the Lower Devonian of Siberia in general and of the Kuzbass in particular.

Our study of the Eodevonian of Altai has made it possible to establish that the composition of the Lower Devonian in Siberia is no less complex than the composition of the Mid—

it. Within the Anui–Kuyagan geosynclinal zone we have established the presence of no fewer than four independent formations, separated by breaks; thus, within the Eodevonian of the Altai no fewer than three phases of tectogenesis are established. This is important not only for the stratigraphy of the Devonian of the Gorny Altai; first, despite the still very limited study of the Devonian deposits of Rudny Altai, within it one can already now outline the manifestation of certain phases of tectogenesis that we have established for the Anui–Kuyagan zone. There can hardly be any doubt that, with further study of the Eodevonian of the Sayan–Altai region, we shall find reflections of these phases in other districts as well.

One further preliminary remark: having established a series of breaks in the composition of the Eodevonian of the Altai, I apply local names to the corresponding phases of tectogenesis. It was indicated above that at present it is impossible to give an exact parallelization of our formations with individual stages and horizons of the European Devonian subdivision; for example, on the basis of all available materials, we must correlate the Kondrat’evskaya Formation with the Lower Coblenzian stage of the Rhenish Slate Mountains, but we cannot now say whether it corresponds to this entire stage or to some part of it. Nor can we be certain that in the future one more (or even more than one) formation, older or younger than the Kondrat’evskaya, but belonging to the same stage, will not be discovered in the Altai. Therefore we cannot be certain that the breaks and phases of tectogenesis established by us correspond exactly in time to the Western European ones. For this reason I prefer to refrain (in most cases) from using European names for the Siberian phases of tectogenesis, all the more because I consider them to be only a regional phenomenon.

The section of the Lower Devonian of the northwestern part of the Altai begins with the Solov’ikhinsk limestone of Gedinnian age. Next follows the Ganinskaya Formation, whose position is likewise quite precisely determined by its fauna: in age it corresponds to the Siegenian stage \((D_1^1)\) of the European subdivision \(D_1\). The fact that the Ganinskaya Formation (its Rensselerian horizon) lies directly upon Silurian rocks indicates the presence of a long break that preceded its deposition, during which the Gedinnian Formation (the Solov’ikhinsk limestone) in places underwent complete denudation. This break corresponds to a phase of tectogenesis that we shall call the Solov’ikhinsk phase. The Ganinskaya Formation is crowned by lagoonal deposits of the Paramfigenievo horizon, while the next younger Kondrat’evskaya Formation, developed in the neighboring Kuyagan district, begins with a basal conglomerate. A new break in sedimentation is revealed quite distinctly, separating these formations and corresponding to a certain new phase of tectogenesis, which we call the Ganinskaya phase. Parallel with the deposition, in the Anui–Ganino graben, of the marine formations \(SD\) and \(D_1^1\), in the Kuyagan district there accumulated the effusive-sedimentary (mainly, apparently, continental) Kuyagan Formation. If our assumption concerning the stratigraphic equivalence of the Ganinskaya and Kuyagan formations is confirmed by further investigations, then, bearing in mind the angular unconformity between the Kuyagan and Kondrat’evskaya formations, we shall have to recognize that the Ganinskaya phase of tectogenesis was accompanied by tangential movements that dislocated the pre-Coblenzian formations.

The question of the break between the Kondrat’evskaya \((D_1^2)\) and Medvedevskaya \((D_1^3)\) formations has already been considered by me (1940, p. 287), and for the corresponding phase of tectogenesis the name Kuyagan phase was proposed.

Putting into a table all the materials at our disposal on the Eodevonian of the Anui–Kuyagan zone, we obtain the following tectono-stratigraphic scheme:

Table 18

Indices	Formation	Horizons, formations, and phases of tectogenesis	Right-side note
$D_{1}^{3}$		Medvedevka Formation: conglomerates at the base; marly sandstones and shales, and sandy limestones with Leptodontella planuscula, Spirifer kopovini, Chonetes pseudobohemica, etc.	Undifferentiated deposits of the Anui–Kuyagan zone (Soloneshnoye, Barancha, village of Bulatovo, etc.).
		Kuyagan phase of tectogenesis	Undifferentiated deposits of the Anui–Kuyagan zone (Soloneshnoye, Barancha, village of Bulatovo, etc.).
$D_{1}^{2}$		Kondratyevka Formation: conglomerate at the base; marly sandstones; massive fine-sandy and clayey rocks with Leptodontella rotundata, Brachyprion speranskii, Probolium altaicum, Pleurodictyum, etc.	Undifferentiated deposits of the Anui–Kuyagan zone (Soloneshnoye, Barancha, village of Bulatovo, etc.).
		Ganin phase of tectogenesis
$D_{1}^{1}$	Ganin Formation	Paramnigenia Horizon: lagoonal greenish-gray sandstones with Amnigenia altaica, Laurskia attenuata, etc. Pseudotogatov Horizon: marly sandstones and shales with open-sea fauna—Leptodontella rotundata, Delthyris perlamellosa, Eospirifer pseudotogatus, etc. Rensseleria Horizon: marly and sandy limestones with Spirifer geyeri, Orthonychia acuta, etc.	Kuyagan Formation: continental sedimentary-effusive sequence with a marine horizon in the lower part.
		Solovikha phase of tectogenesis
$SD$		Solovikha limestones with Atrypa umbra, Atrypa comata, Atrypa insolita, Rhynchospirina formosa, etc.

Chapter II

The Middle and Upper Devonian of the Anuy–Chuya Trough

I. General Characteristics

In comparison with the Lower Devonian, the study of which proved to be a rather difficult and complex matter, the Middle and Upper Devonian of the Altai present considerably fewer difficulties for subdivision and correlation, both within the Altai and with deposits of other regions and countries that are equivalent in the stratigraphic sense. To a considerable degree this is explained by the fact that, in studying the Eodevonian of the Altai, we encountered distinctive faunal assemblages which had not previously been studied and which required much work and a long time to establish their nature and their stratigraphic position. With regard to the Middle and Upper Devonian fauna of the Altai, the situation is considerably simpler, and not only because this fauna, in its composition, is closer (more so than the leptodontellid fauna) to the usual Devonian faunas of Europe and America: as will be shown below, the fauna of \(D_2\) and \(D_3\) also possesses certain very distinctive features, the clarification of which required detailed study. But this study had already been carried out with respect to the Givetian–Upper Devonian faunas of Kuzbass when we began a detailed investigation of the Devonian of the Altai: in a number of my works devoted to the Devonian of the margins of Kuzbass (Khalfin, 1932; 1933; 1933a; 1935), I described and analyzed the fauna from various horizons of \(D_{2}^{3}—D_3\). When geological work expanded in the Altai and paleontological material began to arrive from the Middle and Upper Devonian formations, it became clear that they were characterized by the very same fauna that had been studied from the Devonian deposits of Kuzbass. This made it possible at once, and without particular difficulty, to determine the stratigraphic position of most of the faunistically characterized Middle and Upper Devonian formations of the Altai (Khalfin, 1935).

However, all that has been said above applies only to the Givetian and Frasnian deposits of the Altai; up to the present time the question of the Altai Eifelian remains quite unclear. This is explained to a considerable degree by the fact that the Eifelian faunas of Siberia have still not been studied; therefore, for the Altai at present we cannot indicate Eifelian deposits whose age would be precisely substantiated paleontologically.

Upper Givetian and Lower Frasnian deposits are widely developed in the Altai; they are distributed not only in those regions where Lower Devonian deposits have been encountered (the Anuy–Kuyagan zone and Rudny Altai), but are also present in the central and southeastern parts

of the Altai Mountains. Marine deposits younger than the Lower Frasnian are unknown in the Altai Mountains.

As was already noted above, the study of the Middle and Upper Devonian deposits of the Altai was greatly aided by the possibility of correlating them with the Devonian of Kuzbass, whose fauna had been studied earlier. However, there is also the reverse side of this question: the study of the Devonian of the Altai has made it possible, as we shall now see, to refine and detail certain elements of Devonian stratigraphy that are significant not only for the Altai but also for the entire Sayan–Altai region. The key to understanding the stratigraphy of the Givetian–Frasnian deposits of the Altai Mountains is the Malafeevka Formation, developed in the Kuyagan district, in the Anui–Kuyagan geosynclinal zone; it is characterized in detail below. Here it is sufficient to note the following: this formation embraces the Upper Givetian and Lower Frasnian deposits; field study of them enabled me to establish, within a single section of one conformable sequence, the position of the horizon with Spirifer cheehiel beneath the horizon with Spirifer disjunctus s. str. Thus the stratigraphic position of the most important Upper Givetian guide group of Siberia—the Spirifer cheehiel group—has been precisely determined; in our country it plays the role of the same stratigraphic indicator as Stingocephalus burtini does in other countries. These observations put an end to disputes over the stratigraphic position of the horizon with Spirifer cheehiel (the Chizhel or Dzhelov horizon); since deposits with Spirifer cheehiel are widely distributed not only in the Altai but also in other districts of the Sayan–Altai region, precise fixation of the stratigraphic position of the Dzhelov horizon is important not only for the stratigraphy of the Altai.

The study of the Malafeevka Formation also made it possible to establish another important stratigraphic detail, significant for the subdivision of the Middle Devonian of the Altai; namely, the section of the Malafeevka Formation consists (from bottom to top) of the following faunal beds:

\[ \begin{aligned} D^{3}_{2}\ &\left\{ \begin{array}{l} \text{beds with } Spirifer\ cheehiel\\ \text{beds with } Spirifer\ mucronatus \end{array} \right.\\[6pt] D^{1}_{3}\ &\left\{ \begin{array}{l} \text{beds with } Anthyris\ supraphalaena\\ \text{beds with } Spirifer\ disjunctus\ \text{s. str.} \end{array} \right. \end{aligned} \]

For the time being we cannot extend this succession of beds to the entire Sayan–Altai region; thus, in Kuzbass, apparently, Anathyris supraphalaena and Spirifer disjunctus appear together from the very base of \(D^{1}_{3}\). Likewise, we cannot yet divide the Upper Givetian deposits of Kuzbass and Minusinsk into beds with Spirifer cheehiel and beds with Spirifer mucronatus. But for the Altai this subdivision is of substantial importance, since it makes it possible to clarify certain confused relationships within the Middle Devonian. Thus the succession of faunal beds of the Malafeevka Formation established by us made it possible to reveal the structural character of the Devonian deposits of the Belgebash graben of Central Altai (Yu. Kuznetsov, 1939). Consequently, we can say that the Malafeevka Formation is a certain standard for the Givetian–Frasnian deposits of the Altai Mountains: with it we shall compare all the other Givetian–Frasnian deposits of the Altai.

We give a monographic description of the fauna of the Lower Devonian formations of the Altai Mountains; with regard to the Givetian–Frasnian deposits, one may for the time being confine oneself to a detailed characterization of their fauna, since it is entirely similar to the fauna of the corresponding Devonian horizons of Kuzbass—

which I have described in a number of works. The Upper Givetian deposits of the Altai Mountains are characterized by an assemblage of forms among which the group Spirifer cheehiel plays the most important role; therefore we call this entire fauna the cheehiel fauna, or the Chiel fauna. An equally important role in the Lower Frasnian deposits is played by anathyrids, in particular Anathyris supraphalaena (formerly identified with the European Lower Devonian Anathyris phalaena Phill.); this fauna likewise possesses a number of specific features in comparison with synchronous faunas of other countries, and therefore for it we also use the special name supraphalaena fauna, or Supraphalaena fauna. Below, a characterization will be given of the Chiel and Supraphalaena faunas of the Altai.

We shall review the Givetian–Frasnian deposits of the Altai Mountains by districts; at the same time we shall also consider those older continental and effusive formations that accompany the Givetian–Frasnian deposits and to which a Lower Devonian or Eifelian age is in part assigned. Thus, in the present chapter the presentation of materials on the Middle and Upper Devonian of the Altai Mountains will be given according to the following plan:

a) a brief consideration of the question of the Eifelian of the Altai Mountains;
b) a description of the Malafeev Formation as a certain standard section of the Givetian–Frasnian deposits of the Altai;
c) characterization of the Chiel fauna;
d) characterization of the Supraphalaena fauna;
e) the Devonian of the Korgon Range (Western Altai);
f) the Devonian of the central part of the Altai Mountains (the Belgebash and Kurota grabens);
g) the Devonian of the southeastern part of the Altai Mountains.

In this summary I shall rely mainly on personal observations (the Malafeev Formation), on my own determinations of the fauna, and on an analysis of published materials; all these sources allow me, with sufficient certainty, to outline the composition of the Middle and Upper Devonian deposits of the Altai Mountains. However, this review will not be exhaustive, since I do not have the opportunity to use a number of unpublished materials; furthermore, for reasons beyond my control, some collections of Altai Devonian fauna made in recent years have passed out of my hands, and I have not even had the opportunity to become acquainted with them. Nevertheless, I am convinced that, on the basis of the materials at my disposal, I can present the stratigraphy of the Devonian of the Altai Mountains in a sufficiently complete form—in any case, in a form that will illuminate this question more fully than has been done up to now.

All the Devonian deposits characterized below are confined to the Anuy–Chuya trough and to the local depressions associated with it.

II. On the Question of the Eifelian of the Altai

It cannot be considered accidental that Lower Devonian, Upper Givetian, and Lower Frasnian deposits are known to us in the Altai at many localities, whereas only the scantiest and rather indefinite information is available concerning Eifelian deposits. The almost complete lack of study of the Eifelian fauna of Siberia has only the significance that the Eifelian forms indicated by some authors from one or another locality in the Altai do not always speak with sufficient conviction in favor of the stated age of the corresponding deposits; but the weak development of the latter is an established fact, from which we shall have to draw certain conclusions.

Leaving for special consideration (p. 108) the Chagan-Uzun and Karagem formations of southeastern Altai, which probably are of Eifelian age and represent distinctive deposits of the Karagem inland sea, let us consider the available materials on the Eifelian deposits of other parts of the Anui–Chuya trough.

More or less definite indications of the presence of Eifelian deposits are available for the northern part of the Anui–Ganin graben. B. F. Speransky indicates the development of an Eifelian limestone formation near the village of Solovikha, immediately north of the latter, and also between this village and the middle course of the Ganin spring (Fig. 1). The age of this formation was established on the basis of the following faunal determinations made by K. V. Radugin: Coenites fructicosum Stein., Stromatopora sp., Archimedes sp., Calcalgae. In this small list there is only one determination to species; taking into account the poor state of knowledge of the Eifelian faunas of Siberia in general, it must be said that we can accept the conclusion as to the age of the limestones assigned by B. F. Speransky to the Eifelian only insofar as it was made by K. V. Radugin, the best specialist on the coral fauna of Siberia. It should be recalled, however, that it was precisely from the limestones developed immediately north of the village of Solovikha that M. P. Nagorsky supplied a brachiopod fauna, the study of which showed that it is of Gedinnian age (p. 20). This circumstance does not finally remove the question of the presence of Eifelian deposits in this area. But the need for additional careful field investigations and for additional study of the fauna is quite obvious, with the aim of finally resolving the question of the Eifelian of the Anui–Ganin graben and of distinguishing the limestones of different ages developed in this area—Chagyr \(S^{2}_{2}\), Solovikha \(SD\), Rensselaeriid \(D^{1}_{1}\), and possible Eifelian limestones.

Another area in which faunistically characterized deposits, probably of Eifelian age, have been found is the Kurota graben in the central part of Altai. This graben is filled with a complex assemblage of deposits (see p. 105), and, apparently, the presence within it also of marine Eifelian deposits may be regarded as established; these include, in particular, deposits of the limestone horizon encountered by K. V. Radugin¹ on the pass between the headwaters of the Tytkesken and Kaspa rivers (tributaries of the Katun River); this horizon is hereafter called the Tytkesken horizon. In this horizon were found stromatoporoids and bryozoans that remained undetermined, as well as representatives of the genera Darwinia and Heliolites; with respect to the latter genus K. V. Radugin notes that its representatives are similar to those from the Salair calcareous deposits, and indicates that “the most ancient visible beds of the Kurota graben apparently belong to \(D^{1}_{2}\).” There is every reason to regard this evidence with confidence; but it must be greatly regretted that the fauna of the Tytkesken horizon has not been studied in detail: the presence in Altai of faunistically characterized Eifelian deposits, as already noted, is a great rarity, and up to now the Eifelian fauna of Altai remains unknown to us even in a first approximation.

I know of no other areas of the Gorny Altai in which faunistically characterized Eifelian deposits have been established; exactly the same is true of the Eifelian of Rudny Altai.

With regard to the Gorny Altai, from the scanty materials available we may draw the following conclusions:

¹ See the footnote on p. 101.

1) the presence of faunistically characterized Eifelian deposits in the Altai Mountains may be regarded as established, although still requiring further confirmation;

2) the Eifelian deposits in the Altai Mountains have survived only in the form of very small patches, occurring much more rarely than the Upper Givetian and Frasnian deposits;

3) nevertheless, they show that formerly the marine Eifelian deposits were developed within the Altai over a more considerable area than the Lower Devonian: Eifelian deposits are known not only in the northwestern part of the Altai (the Anui–Kuyagan zone), but also in Central Altai (the Kurota graben);

4) the Eifelian deposits are overlain by Givetian deposits, in particular by faunistically characterized Upper Givetian deposits, which everywhere lie transgressively upon more ancient deposits; faunistically characterized Lower Givetian deposits in the Altai Mountains are not known.

All this presents to our imagination the following picture: at one time the Eifelian marine basin occupied a considerable area in the Altai. From the Anui–Kuyagan geosynclinal zone it extended, along the Anui–Chuya depression, in the form of a bay rather far to the southeast, into Central Altai. But after its retreat there followed a prolonged continental interval, during which the deposits of the Eifelian Altai sea were denuded almost completely. Thus, those fragments of Eifelian marine deposits that are now available for study testify to a certain, almost lost page in the Devonian history of the Altai. They deserve all the more attention; their further study must be organized in connection with the study of Eifelian deposits in other parts of the Sayano-Altai region, since at present it is precisely for the lower half of the Middle Devonian that we possess the most schematic and fragmentary information.

III. The Malafeev Formation

This formation, as was already indicated above, is a certain standard for the correlation of the Givetian–Frasnian deposits of the Altai Mountains. Deposits of the formation are developed in the Kuyagan district, in the upper reaches of the Tikhaya River, east of the village of Aleksandrovka, and along the Malafeev creek, a right tributary of the Gremishka River, which flows into the Peschanaya River near the village of Kuyagan (see Fig. 4). The Devonian rocks here form a syncline whose axis has a northwestern strike and plunges to the southeast. The general characteristics of the Malafeev Formation were given by me (1932, pp. 4–6) in the following form.

On the northeastern limb of this syncline (along the tops of the right tributaries of Malafeev creek) it may be observed that Devonian rocks lie transgressively (through a conglomerate) upon the effusive-sedimentary Kuyagan Formation (p. 44). Above the conglomerate are exposed greenish-gray sandy, clayey schists and argillites, not effervescing with HCl, and containing, among other brachiopods, large spirifers of the group Spirifer cheehiel Kon. The strike of these rocks is 295°, the dip is to the SSW at an angle of 55°. These are the lowermost horizons of the Malafeev Formation.

Higher horizons are composed of clayey schists having the same bedding and containing a numerous and diverse fauna of Middle Devonian brachiopods, but already without spirifers of the group Spirifer cheehiel. The section ends with an exposure situated above the very bed of Malafeev creek. Here a bed of greenish- and bluish-gray calcareous argillite is exposed, already containing a Lower Frasnian fauna, Anathyris supraphalaena. In this exposure the rocks have a strike of 290° and dip to the SSW at an angle of 52°.

The total thickness of the Middle and Upper Devonian rocks in the characterized section is not less than 750 m. All these rocks exhibit meridional jointing with vertical dip.

In the upper reaches of the Tikhaya River there is another section of the formation. Here the core of the syncline and its southwestern limb are exposed. In the core of the syncline (east of elevation 6.3 m, Kuchkovskii) [[unclear: text continues on next page]]

includes dark, bluish-gray argillaceous shales and gray argillaceous limestones with Spirifer disjunctus s. str. These rocks are extremely strongly shaly and can be broken apart by hand. They lie almost horizontally (with a dip of a few degrees to the N or NE).

The southwestern limb of the syncline, in lithological and faunal respects, fully repeats the northeastern limb (only the bed of calcareous argillite with Anathyris supraphalaena is not exposed). However, beneath the shales with Spirifer cheehiel the conglomerate is not found here, and in the southwesternmost limb several small disturbances are observed, expressed in abrupt changes in the attitude of the rocks of this limb over short distances. This is connected with the character of the southwestern boundary of the rocks under consideration; this boundary is tectonic: over the Middle Devonian rocks, from the southwest, rocks of the same Kuyagan formation are thrust, upon which \(D^{3}_{2}\) lies transgressively in the above-described section along the right tributaries of the Malafeev Creek.

The continuation of the characterized Devonian rocks to the northwest was not traced by the author. According to an oral communication from B. F. Speranskii, the syncline under consideration in this direction quickly closes or is truncated by some disjunctive fault. From the southeast, onto the Malafeev formation (and in general onto all rocks of the right bank of the Tikhaya River near the village of Aleksandrovka) are thrust rocks of the Upper Silurian limestone–phyllite unit.

For more detail on this disturbance see p. 64. For the plan and schematic section of the described syncline see Khalfin, 1935, figs. 1 and 2, pl. I.

The fauna of the Malafeev formation is diverse. It is decidedly dominated by brachiopods, represented by the families Spiriferidae, Athyridae, Camarotoechiidae, Dalmanellidae, Strophomenidae, and Productidae. Among them we encounter European, Asiatic and, lidne, American forms.

The lowest horizons of the formation, cropping out at the head of the Malafeev Creek and composed of fine-grained sandstones, contain a rather numerous brachiopod fauna. The most characteristic are large specimens of Spirifer cheehiel Kon. var. altaica. Along with these spirifers there occur Cyrtina heteroclita Defr., Productella spinulicosta Hall, Stropheodonta pseudasedla Khalf., and others.

In higher horizons a numerous fauna has also been found, in which Middle Devonian forms predominate, but Upper Devonian species already appear (although in very small numbers). Spirifer cheehiel is no longer encountered here. In its place, Spirifer mucronatus Hall is widely distributed; the Altai representatives of it are quite similar to typical American and German specimens of this species (Quiring, 1914), possessing a broad, undissected flat fold and the same weakly sinuous median sulcus. In addition to S. mucronatus, numerous Productidae occur (Productella spinulicosta Hall, Productella productoides Murch., Chonetes sp.); the Camarotoechiidae are also numerous (Leiorhynchus kellogi Hall, L. protractus Dav., and others), as are Strophomenidae ex gr. S. interstrialis Phill. and others. Along with the listed forms, two specimens were found belonging to spirifers of the group S. disjunctus Sow.

The next horizon, sharply distinct faunistically from the preceding one, is the horizon with Anathyris supraphalaena n. nom. and Anathyris peetzi Khalf.; both of these species are characteristic of the Lower Frasnian deposits of Siberia. Along with them occur Douvillina dutertrii Murch., Pterinea flabella Conr., solitary corals, and some others.

Finally, in the closure of the syncline, as already mentioned, shales with thin interbeds of limestone crop out, in which Spirifer disjunctus s. str. was found, characterizing the lower half of the Frasnian stage.

This brief review of the fauna of the Malafeev formation is quite sufficient to show that this fauna is quite ordinary for Western Siberia: deposits of different ages in the Kuzbass and the Minusinsk Basin contain, in general, a quite similar fauna.

Thus, in the Kuyagan district we have Upper Givetian and Lower Frasnian deposits, forming a unit about 800 m thick. In this unit the following horizons can be distinguished faunistically:

\[ D^{1}_{3} \begin{cases} \text{Bed with } *Spirifer disjunctus*\\ \text{Beds with } *Anathyris supraphalaena* \end{cases} \]

\[ D^{3}_{2} \begin{cases} \text{Beds with } *Spirifer mucronatus*\\ \text{Beds with } *Spirifer cheehiel* \end{cases} \]

In the described section of the Malafeev formation, one detail attracts attention, concerning the boundary between \(D^{3}_{2}\) and \(D^{1}_{3}\): with complete conformity in the attitude of the rocks, this boundary is marked by a rather abrupt change of facies. Namely, above and below the bed with Anathyris supraphalaena lie dark, thin-bedded argillaceous shales with an abundant fauna of spiriferids, dalmanellids, productids, and camarotoechiids. The bed itself with Anathyris

supraphalaena is composed of a markedly different rock—a very light, bluish-greenish, massive, strongly calcareous argillite with numerous atrypids.

Such a change of facies has, of course, its cause; let us note that in some localities of Altai (the Korgon Range) the Upper Zhivetian deposits, equivalent to the lower part of the Malafeev Formation, are not accompanied by the Lower Frasnian, as is the case in the section of the Malafeev Formation considered here. We see in this the expression of a certain upward movement of Altai, which took place at the boundary between \(D_2\) and \(D_3\) and corresponds to the Barsas phase of tectogenesis (Usov, 1936, p. 137). This movement was not significant and only partially brought above sea level the territory that had been occupied by the latter; in part, however, the marine regime continued to exist, primarily within the Anui–Kuyagan geosynclinal zone. But here too the indicated movement was reflected, causing the facies change noted above precisely at the boundary between \(D_2\) and \(D_3\). This circumstance might perhaps be used to divide the Malafeev Formation into two independent units; however, there is no break in sedimentation between the Middle and Upper Devonian parts of this formation, and therefore we refrain from such a division.

The Malafeev Formation and the Devonian deposits corresponding to it in other regions of Altai are characterized by the chechiel fauna in their Middle Devonian part and by the supraphalaena fauna in the Upper Devonian. Before proceeding to a further review of these deposits, we shall give a general characterization of the faunal assemblages mentioned.

The type section of the Malafeev Formation is the section along Malafeev Spring, the right tributary of the Tremishka River, which flows into the Peschanaya River above the village of Kuyagan.

IV. Characterization of the Chechiel Fauna of Western Siberia

All Upper Zhivetian deposits of the Gorny Altai are characterized by a rich and diverse fauna, in which the principal place belongs to the group Spirifer cheehiel; the Altai Chechiel fauna is part of a single, widely distributed Upper Zhivetian fauna of the Sayan–Altai system. I have already had occasion, in a special article (Khalfin, 1937), to characterize this fauna. But since the publication in which that article appeared had a very limited circulation, and since the Chechiel fauna plays a primary role in the Altai Devonian, I consider it necessary to give here a number of excerpts from the above-mentioned article, supplementing them with remarks that concern specifically the Devonian of Altai.

In Siberia three areas of distribution of the Chechiel fauna are known: the northern and northwestern margins of the Kuznetsk Basin, Altai, and the Minusinsk Basin.

The classic locality of the fauna of interest to us is the village of Lebedyanskoye, situated on the Mazalovsky Kitat River, near (to the west of) the town of Anzhero-Sudzhensk. Here spirifers of the group Spirifer cheehiel occur in enormous numbers, constituting the most conspicuous element of an altogether very rich and diverse brachiopod fauna. Their mass development is accompanied by diversity of species composition: in the Lebedyanskoye Devonian this group is represented by seven different forms. In general, in terms of the number and diversity of representatives, the Lebedyanskoye Devonian is apparently the only locality of the group Spirifer cheehiel of its kind. South and southwest of the village of Lebedyanskoye, fauna with spirifers of this group has been encountered at a number of points along the northwestern margin of the Kuznetsk Basin.

Over a considerably larger area than in the Kuzbass, Devonian deposits with the Chechiel fauna are developed in Altai: here the Upper Zhivetian are absent—

... deposits, which in their brachiopod facies would not contain spirifers of the Sp. cheehiel group and their usual associates. The first indication of the presence of Spirifer cheehiel together with Atrypa reticularis and Cyathophyllum cf. caespitosum in the Altai was made by P. Pilipenko (1915, p. 96) for the Devonian deposits of the Korgon Range (Western Altai). V. P. Nekhoroshev (1932, p. 63) described a section of Devonian deposits with the fauna of Sp. cheehiel along the Chuya River, below the mouth of the Belgebash River; this section was studied in greater detail by Yu. A. Kuznetsov (1939).

In the Northern Altai, Givetian deposits with cheehiel fauna are developed in the basin of the Peschanaya River near the village of Kuyagan; here they are represented by the Malafeev Formation described above. In western Altai this group has been found by a number of Siberian geologists in deposits forming part of the northern slope of the Korgon Range. In southeastern Altai, in the headwaters of the Chuya River and along its tributaries, abundant cheehiel fauna was collected by P. S. Krasnopeeva. K. V. Radugin discovered deposits with this fauna in the Kurota graben of Central Altai.

There can hardly be any doubt that, with further geological investigations in the Altai, the number of localities yielding the cheehiel fauna will increase; but the materials already available are sufficient to assert that the Givetian basin of the Anuy–Chuya trough was inhabited by a fauna in which the group Spirifer cheehiel played a prominent role.

The Minusinsk fauna with Spirifer cheehiel has long been known; in 1886 it was described by A. Stuckenberg. In this fauna the group Sp. cheehiel is present in an enormous number of specimens and occurs everywhere that limestones of the corresponding age are developed. Its classic locality is the village of Beyskoye, about 100 km southwest of the city of Minusinsk, and from the name of this village the fauna received the name “Beysk fauna.”

Turning to the Givetian deposits developed west of the Minusinsk–Kuznetsk–Altai region, we must first of all note the disappearance of the Spirifer cheehiel group already in Kazakhstan. The fauna of the Givetian deposits of Kazakhstan, unfortunately, has not been described, but the detailed lists of forms from these deposits given by N. G. Kassina (1930, pp. 78–90) do not contain the group of brachiopods that interests us. This group is likewise absent in Turkestan and in the Urals, and still more so in Europe. As a rough approximation, the western boundary of the distribution of the cheehiel fauna may be considered the 80th meridian east of Greenwich.

It is extremely difficult to say anything definite about the distribution of this fauna east of the Minusinsk depression, since the Devonian fauna of Eastern Siberia and the Far East has been studied quite insufficiently—or rather, has not been studied at all.

Regarding the distribution of the Spirifer cheehiel group beyond Siberia, the literature available to me contains no reasonably detailed indications. The first specimens of Sp. cheehiel, described by L. Koninck and E. Kayser, came from China, but were acquired by travelers in Shanghai pharmacies, since in China medicinal properties were attributed to fossils. Grabau (1923–24, p. 162) notes that “Spirifer cheehiel—typical Chinese form,” and A. N. Krishtofovich (1932, p. 270) writes that “in the Middle Devonian, in the Chinese basin, a distinctive fauna develops with such a representative as Sp. cheehiel,” but these authors do not provide data on the horizontal distribution of this species in China. A direct indication of the presence of Sp. cheehiel in the Givetian deposits of Yunnan is found in the work of J. Fromaget and E. Saurin (1930, p. 318). In America Sp. cheehiel has not been found.

Thus, two basins inhabited by a fauna with Sp. cheehiel are outlined—the Minusinsk–Kuznetsk–Altai and the South Chinese.

The richest and most diverse, and at the same time the most thoroughly studied, is the Chiele fauna from the village of Lebedyanskoye. Here, besides brachiopods, coelenterates and bryozoans are very widely distributed; mollusks and trilobites are considerably less numerous. The brachiopods of this fauna were described by me (1937), the corals by K. V. Radugin (1937); the remaining fauna has not been treated. We shall give a characterization of the Chiele fauna, beginning with the fauna from the village of Lebedyanskoye.

Within the brachiopod fauna from the village of Lebedyanskoye 75 forms have been established. The largest percentage (37%) is made up of new forms, in addition to which this fauna contains another 7 forms that are specifically Asiatic.

European forms play a very large role (30.9%) in the Lebedyanskoye fauna, which is characteristic also of the Devonian fauna of Asia in general; this circumstance has led some authors to assume an influx of European fauna into Asia throughout the entire Devonian period. For the Upper Givetian basin of Siberia this assertion cannot be accepted, and, as will be seen below, the abundance of European forms in the composition of the Chiele fauna of Siberia has another explanation. American species in the Lebedyanskoye fauna constitute 13.8% and are represented by such characteristic forms as Spirifer mesocostalis Hall, Schuchertella chemungensis Conr., Rhipidomella vanuxemi Hall, and others. Forms with universal distribution make up 7.5%, namely: Leptaena rhomboidalis Wilck., Schizophoria striatula Schl., Spirifer undifer Roem., Atrypa reticularis L., A. desquamata Sow.

The coelenterates of the Lebedyanskoye Devonian were studied by K. V. Radugin. He described 48 forms: 20 of them belong to Rugosa, 20 to Tabulata, and 8 to Stromatoporoidea. This fauna is striking in its peculiar character: of the 48 forms, 31 are new; in particular, K. V. Radugin established two new genera—Natalophyllum and Neoroemeria. In general, the coral horizons of the Lebedyanskoye Devonian lie below the brachiopod horizons; however, analyzing the coelenterate fauna, K. V. Radugin comes to the conclusion that it is of Givetian age and allows the possibility of an Upper Eifelian age only for the very lowest beds of the Lebedyanskoye Devonian.

The Altai Chiele fauna has not been described, but it has been precisely established that it has the same character. In Table 19 the composition of this fauna from various parts of the Gorny Altai is presented in comparison with the fauna from the village of Lebedyanskoye.

In the Northern Altai, spirifers of the group Sp. cheehiel are fairly numerous in the Malafeevo Formation and at times attain gigantic dimensions—up to 140 mm in width. The North Altai Sp. cheehiel are in all respects similar to the Lebedyanskoye forms, but the internal molds of the ventral valves in the former display certain peculiarities: the muscular boss in the Altai specimens is divided by a deep and narrow depression, whereas in the Lebedyanskoye specimens its surface is almost even and has only a very weakly expressed, broad and flat depression. This difference is maintained so consistently in all specimens, both large and small, that I have separated the Altai forms into a certain local variety—Sp. cheehiel var. altaica. Besides this form, in the Givetian deposits of the Northern Altai there is present Spirifer cheehiel var. alata Stuck.; some internal molds of dorsal valves, with their laterally compressed, pointed saddle, very much resemble Spirifer bidevexus Khalf. or Spirifer mirabilis Khalf.

Together with spirifers of the group Sp. cheehiel, the following forms occur:

    Productella spinulicosta Hall
        subaculeata (Murch.)

Table 19

No.	Names of forms	Lebedyan Formation	Korgon-Slovsk Formation	Belerebash Formation	Kurota Formation	Malafeev Formation	Kyzylshinsky Horizon
1	Chonetes coronata Conr.	+	+	?	−	−	−
2	Chonetes cf. subcancellata Reed	1	−	−	−	−	−
3	Productella subaculeata (Murch.)	+	+	−	+	+	+
4	Productella spinulicosta Hall	+	+	+	+	+	+
5	Productella productoides (Murch.)	−	−	−	+	+	+
6	Stropheodonta pseudasella n. nom.	⊕	+	+	−	+	+
7	Dictyostrophia reticularis (Khalf.)	+	−	−	−	−	−
8	Douvillina sp.	1	−	−	−	−	−
9	Leptaena rhomboidalis Wilck.	⊕	+	−	−	−	+
10	Schellwienella umbraculum (Schl.)	⊕	+	+	−	−	+
11	Schuchertella chemungensis (Conr.)	+	−	−	−	−	−
12	″ eifeliensis (Vern.)	⊕	+	+	−	−	+
13	″ subtetragona (Gür.)	+	−	−	−	−	−
14	Isorthis sibirica (Khalf.)	⊕	+	+	+	+	+
15	Rhipidomella vanuxemi (Hall.)	⊕	−	−	+	−	−
16	Schizophoria striatula (Schl.)	⊕	+	−	−	−	+
17	Kayserella ramosa Khalf.	+	−	−	−	−	−
18	Uncinulus korovini Khalf.	⊕	+	−	−	−	+?
19	″ (?) subsignatus Reed.	+	−	−	−	−	−
20	″ (?) concentricus Khalf.	1	−	−	−	−	−
21	Cryptonella planirostra Hall.	+	−	−	−	−	−
22	″ rhomboidea Khalf.	1	−	−	−	−	−
23	″ cf. jucunda Hall.	1	−	−	−	−	−
24	Trigeria lata Khalf.	1	−	−	−	−	−
25	Spirifer cf. cabedanus V. et A.	+	+	−	−	+	−
26	″ mesacostalis Hall.	+	+	−	−	−	−
27	″ cf. argentarius Meek	1	−	−	−	−	−
28	″ undifer Roem.	+	−	−	−	−	−
29	″ martianoffi Stuck.	−	+	+?	−	−	+
30	″ kussbassica Kas.	1	−	−	−	−	−
31	″ cheehiel Kon.	⊕	+	+	+	+	+
32	″ cheehi Kon. var. altaica Kh.	−	+	+	+	+	−
33	″ ″ alata Stuck.	+	−	−	−	+	−
34	″ bidevexus Khalf.	+	−	−	−	+	−
35	″ mesolobus Korovin	+	−	−	−	−	+
36	″ semicostalis Khalf.	+	−	−	−	−	+
37	″ mirabilis Khalf.	1	−	−	−	+?	−
38	″ cultrijugatus Khalf.	−	−	−	−	−	+
39	″ orthogonalis Khalf.	+	−	−	−	−	−
40	Delthyris altschedatiensis (Korovin)	⊕	−	−	−	−	−
41	″ robusta (Barr.)	+	−	−	−	−	−
42	Eoreticularia aviceps (Kays.)	1	−	−	−	−	−
43	Lamellispirifer mucronatus (Conr.)	−	−	+	+	+	−
44	Cyrtina heteroclita (Defr.)	1	−	−	+	+	+
45	″ ″ var. multiplicata Dav.	1	−	−	−	−	−
46	″ ″ var. intermedia Oehl.	+	+	+	+	−	+
47	Merista plebeia (Sow.)	+	−	−	−	−	−
48	″ lacryma (Sow.)	+	−	−	−	−	−
49	Meristella nasuta (Conr.)	+	−	−	−	−	−
50	″ yanischewskii Khalf.	1	−	−	−	−	−
51	Athyris subacuminata Khalf.	⊕	−	−	+?	−	−
52	″ concentrica Buch.	+	+	+	+	−	−
53	″ fultonensis Swall.	+	+	−	−	−	+
54	″ rugata Dav.	+	−	−	−	−	−
55	″ glassi Dav.	1	−	+	−	−	−
56	″ polita Hall.	1	−	−	−	−	−
57	″ gracilis Sandb.	1	−	−	−	−	−
58	″ circularis Khalf.	⊕	+	+	−	−	−
59	″ cf. triplezioides Oehl.	+	−	−	−	−	−
60	″ trapezoidalis (Peetz)	+	−	−	−	−	−
61	Anathyris resupinata Khalf.	+	−	−	−	−	−
62	″ simplex Khalf.	+	−	−	−	−	−
63	″ athyroides Khalf.	+	−	−	−	−	−
64	″ triloba Khalf.	1	−	−	−	−	−
65	″ helmersenii (Buch.)	+	−	−	−	−	−
66	Retzia nana Khalf.	+	+?	−	−	−	−
67	″ lopatini (Stuck.)	+	−	+	−	−	−
68	″ cf. prominula (Roem.)	+	−	−	−	−	−
69	″ kayseriaeformis Khalf.	1	−	−	−	−	−
70	Atrypa reticularis (Linn.)	⊕	+	+	+	+	+
71	″ desquamata Sow.	⊕	+	−	−	−	+
72	″ sinensis Kays.	+	−	−	−	−	−
73	″ tubaecostata Paeck.	+	−	−	−	−	−
74	″ spinosa Hall var. nana Khalf.	+	−	−	−	−	−

Productella productoides (Murch.)
Isorthis sibirica Khalf.
Schizophoria striatula (Schl.)
Cyrtina heteroclita (Defr.)
Spirifer bidevexus Khalf.
Spirifer cabedanus Vern. et Arch.
Athyris concentrica Buch
Fenestellidae
crinoid columnals,

and in the higher beds of the Malafeev Formation, where spirifers of the Sp. cheehiel group are very rare, Spirifer mesocostalis Hall, Spirifer mucronatus Conr., Atrypa reticularis L., Stropheodonta pseudasedla Vern., Leiorhynchus kellogi Hall, and others appear in large numbers. In the overwhelming majority, these forms are common to the Lebedyan fauna.

From Western Altai (the Korgon Range) I have a small collection of Givetian brachiopods, among which there are several specimens of typically expressed Spirifer cheehiel, as well as Spirifer cheehiel var. alata. They are associated with the following brachiopods: Leptaena rhomboidalis, Schellwienella umbraculum, Schizophoria striatula, Aulacella eifeliensis, Uncinulus korovini, Spirifer martianoffi, and others; the most widespread form is Spirifer martianoffi. In the Korgon D\(^3_2\), coelenterates are very numerous; pelecypods occur occasionally (Conocardium cuneus Hall, Cypricardinia lima Schnur).

In Southeastern Altai, besides the typical Sp. cheehiel, Spirifer semicostalis Khalf., Spirifer mesolobus Korov., and a certain local form named Spirifer cultrijugatifomis Khalf. have been found. Together with Sp. cheehiel in Southeastern Altai, rather diverse brachiopods have been found—Leptaena rhomboidalis, Schizophoria striatula, Isorthis sibirica, Productella spinulicosta, Productella productoides, Athyris concentrica, Atrypa reticularis, and others; as in the Korgon fauna, representatives of the species Spirifer martianoffi Stuck. are very numerous.

The Givetian fauna of the Minusinsk Basin was described by A. Stuckenberg; using this description and the small collection available to me, I can give the following characterization of the composition of this fauna. The most widespread species are Spirifer cheehiel and Spirifer martianoffi. The former is represented by the typical form and the variety alata; there is also Sp. bidevexus. Further, in this fauna occur Retzia lopatini Stuck., Emanuella takwanensis Kays., Athyris concentrica Buch, Spirifer schmidti Stuck., Atrypa reticularis L., productellids, a certain species of the genus Schuchertella or Streptorhynchus (“Streptorhynchus crenistria” of Stuckenberg), as well as Crania obsoleta Goldf. More detailed lists of the Minusinsk Devonian fauna are given in the summary by Ya. S. Edelstein (1932, p. 26).

Comparing the Givetian fauna from all the regions considered above, we must first of all note that this fauna is uniform in all these regions, connected not only by the presence of a distinctive group of spirifers, but also by a large number of other forms. Further, in this fauna there is a large number of local forms—up to 30% and more in the various regions. But alongside this, a very large percentage of the forms in the Siberian cheehiel fauna consists of European forms; moreover, the influence of the American fauna is also noticeable. It is important to note the absence in the fauna analyzed of such typical Givetian forms as Stringocephalus burtini, as well as Uncites gryphus.

The absence of these cosmopolitan Upper Givetian forms in the cheehiel fauna of Siberia, and, on the other hand, the complete absence of the Spirifer group

cheehiel west of the 80th meridian indicate the isolation of the Upper Givetian basin of the Sayano-Altai region from the seas of Europe, the Urals, and Central Asia, in which the influence of the Zaysan geosyncline is expressed (p. 121).

Alongside the above-noted features of similarity in the chyazelian fauna of the various regions, we must also note the existing differences, which are generally insignificant and apparently should be explained by facies causes; thus, Sp. martianoffi, very numerous in southeastern Altai, in the Korgon Range and the Minusinsk Basin, is very rare in the Lebedyanka Devonian and is completely absent in the Devonian of northern Altai (the Malafeevka Formation). Schellwienella umbraculum is widely distributed in the Lebedyanka and the Korgon Range and has not been found at other localities. Schizophoria striatula is absent in the Minusinsk Basin, etc. To illustrate these differences, the following table of distribution of the most common forms may be given:

Table 20

Species name	Lebedyanka	Northern Altai	Western Altai	Southeastern Altai	Minusinsk Basin
Sp. martianoffi	very rare	absent	widespread	widespread	widespread
Lept. rhomboidalis	widespread	absent	widespread	widespread	absent
Sch. umbraculum	widespread	absent	widespread	absent	present
Atrypa reticularis	widespread	rare	widespread	widespread	widespread
Retzia lopatini	rare	absent	?	rare	widespread
Ath. concentrica	widespread	absent	present	present	present
Pr. subaculeata	rare	widespread	rare	widespread	a closely related form is present

That these differences depend on facies differences is also confirmed by the character of the corresponding deposits and fauna.

The abundance, in the Siberian chyazelian fauna, of European forms at first glance appears to contradict the observation made above concerning the isolation of the Upper Givetian basin of Siberia from the Ural and Turkestan basins (and consequently from the European basin as well). However, closer examination of the European components of the chyazelian fauna provides an explanation for this seemingly paradoxical circumstance. Namely, analysis (which we shall not repeat here) of the vertical distribution of the European forms included in the chyazelian fauna shows that all of them could have penetrated into the Kuznetsk-Altai-Minusinsk basin in pre–Upper Givetian time.

This compels us to draw the following conclusions: the similarity of the chyazelian fauna with the European one is inherited from the Eifelian and, possibly, Lower Givetian epoch; the absence in this fauna of such cosmopolitans capable of the broadest dispersal as Str. burtini and Uncites gryphus, together with an abundance of indigenous species and especially of the group Sp. cheehiel, indicates that in Upper Givetian time the influx of European forms into the Siberian basin from Europe and Turkestan had ceased, i.e., that the former, in Upper Givetian time, was isolated from the latter.

Let us sum up. The Upper Givetian deposits of Siberia, in particular of Altai, are characterized by a fauna possessing highly remarkable distinguishing features of both negative and positive character. The former include the complete absence from it of the most widespread and popular guide forms of the Givetian division of the Mesodevonian—the species Stringocephalus burtini and Uncites gryphus, which occur in masses—

for example, in the synchronous deposits of neighboring regions of Central Asia. They are replaced by a distinctive group of spirifers, the best-known representative of which is Spirifer cheehieli; this group gives the fauna in question its most characteristic and distinctive features.

In its geographic type, the Chieh fauna in some respects resembles the Lower Devonian leptodontellid fauna: in it, local forms likewise play a significant role, European species are present in large numbers, and North American ones in smaller numbers. But the Chieh fauna is distributed much more widely geographically: the leptodontellid fauna is known to us only within the northwestern and western parts of Altai, whereas the Chieh fauna extends as far as southeastern Altai inclusive and along the margins of the Kuznetsk and Minusinsk basins, as well as in China.

Using the example of the cheehieli fauna, we are again convinced of the considerable distinctiveness of the Devonian organic world of Siberia; we shall now see that this distinctiveness is also preserved in the Upper Devonian, and thus, for \(D_2^3\) and \(D_3^1\), a quite definitely characterized Sayano-Altai zoogeographic province is revealed. Let us become acquainted with the composition of the population of this province in Lower Frasnian time.

V. Characterization of the Supraphalaena Fauna of Western Siberia

The fauna of the Lower Frasnian deposits of Siberia, as regards brachiopods, is sufficiently well known to us, chiefly, again, from the Devonian materials of Kuzbass (Khalfin, 1932; V. Khalfina, 1940). And, just like the Upper Givetian fauna, this fauna in the Altai Mountains has the same composition as in Kuzbass. The most characteristic feature of this fauna is the abundance in it of anathyrids, in particular the wide distribution of the species Anathyris supraphalaena, after which, for brevity, we shall call this fauna the supraphalaena fauna.

This fauna is in some respects substantially different from the Chieh fauna and, still more, from the leptodontellid fauna. First, the supraphalaena fauna, in its main mass, is a typical European fauna; this does not mean, of course, that local forms are absent from it. But neither the comparatively low percentage of the latter nor the isolated American species can obscure the entirely clear European type of this fauna. Moreover, in comparison with the Chieh fauna, this difference is deeper and more important than merely the different quantitative content of European forms in them: in the Chieh fauna, among its quite numerous European components, precisely the index species are absent: Stringocephalus burtini, Uncites gryphus, etc.; whereas in the supraphalaena fauna, among the European forms, it is precisely the most important index groups that are widely developed, for example—the Spirifer disjunctus group and the Spirifer zickzack group. Nevertheless, our Lower Frasnian fauna possesses certain features so distinctive that distinguishing it from synchronous European (and not only European) faunas appears both easy and necessary (we emphasize this difference from the European Lower Frasnian fauna, in particular, by giving it a special name).

Within the Lower Frasnian fauna of Siberia, the following groups are most widely distributed:

a) productellids, in particular—Pr. subaculeata Murch., Pr. arctirostrata Hall and Pr. spinulicosta Hall; of these, in the Givetian-Frasnian deposits of Altai the last is especially frequent;

b) stropheomenids from the group Stropheodonta asella Vern.—Douvillina dutertrei Murch.;

c) spirifers of the group Spirifer disjunctus = Cyrtospirifer Nal.; this important cosmopolitan group, in stratigraphic terms, is represented in the Suprafalaenian fauna by the species Spirifer disjunctus Sow., Spirifer tenticulum Vern., Spirifer subconоideus Khalf., to which, as a rare form, Spirifer archiaci Murch. is sometimes added;

d) spirifers of the group Spirifer zickzack = Gürichella Drev.; this group (together with the two preceding ones) most reliably determines the Lower Frasnian age of the Suprafalaenian fauna; here we find such typical forms as Sp. zickzack Roem., Sp. multifidus Scup., Sp. deflexus Roem., Sp. acutulus Khalf.

e) athyrids of the group Athyris concentrica Buch; the athyrids in this fauna are less diverse than in the Chiale fauna, but are very numerous;

f) peculiar athyrids, though vicariant with European species of athyrids, which I unite (Khalfin, 1946) under the new generic name Plicathyris and about which a few additional words will be said below;

Fig. 11. a—Plicathyris sibirica (V. Khalf.); \(D_3^1\), Western Siberia. b—Plicathyris ezquerra (V. et A.); \(D_1\), Western Europe. c—Plicathyris chachlovi Khalf.; \(D_3^1\), Western Siberia.

g) anathyrids, which are one of the most important groups of this fauna; we shall also speak of them further below;

h) a group of endemic ribbed athyrids, of which the most important are Retzia tschernyschewi Peetz, Retzia ussiensis Tolm. and Retzia korovini V. Khalf.

i) atrypids of the group Atrypa reticularis Linn. s. l.

Of the fossil groups listed above, the most important (in the sense of establishing the most typical features of the fauna under analysis) are the athyrids. In particular, many athyrids of the Suprafalaenian fauna have a superstitid character. Thus, representatives of the genus Plicathyris—Plicathyris sibirica V. Khalf., Plicathyris chachlovi Khalf. and certain others—are closely vicariant with European forms distributed in \(D_1\) and \(D_2^1\) (fig. 11); likewise, the anathyrids, which belong among the most—

Fig. 12. a—Anathyris phalaena (Phill); \(D_1\)--\(D_2^1\), Western Europe. b—Anathyris suprafalaena Khalf.; \(D_3^1\), Western Siberia.

—widespread forms of the Suprafalaenian fauna, have their closest analogues in Europe only among Lower Devonian forms (fig. 12). We dwell on the analysis of this question elsewhere (Khalfin, 1946); here it is enough to note that a distinctive feature of the Suprafa-

of the phalaenid fauna, sharply distinguishing it from all stratigraphically equivalent faunas, is the wide distribution in it of superstitid¹ elements, among which, first of all, are the anathyrids. There is no other Lower Frasnian fauna which in this respect would be similar to the supraphalaenid fauna; even in neighboring regions (Kazakhstan, Central Asia, China) anathyrids and plicathyrids are entirely absent from Upper Devonian (and generally from Devonian) faunas. Thus, we see that although the supraphalaenid fauna, in its composition, is a fauna of the European type, the composition of European forms in it is very distinctive: alongside typical Upper Devonian forms, elements no less typical of the European Lower Devonian are widely developed in the supraphalaenid fauna (the genera Anathyris and Plicathyris). Here we are once again convinced of the distinctive composition of the fauna of the Sayano-Altai zoogeographic province.

The supraphalaenid fauna characterizes the very lowest part of the Frasnian stage, usually called the phalaenid horizon (A. V. Tyazhnov), after the form that was formerly identified with the European Anathyris phalaena Phill.; as we have shown elsewhere,² however, it is more correct to separate this Upper Devonian Siberian form from the Lower Devonian European Anathyris phalaena and to call it Anathyris supraphalaena; in this connection we also replace the name of the corresponding horizon with supraphalaenid horizon. As detailed studies by V. K. Khalfina have shown (1940, p. 497), the supraphalaenid horizon may, on faunal grounds, be subdivided in turn into two parts: a lower one, which may be regarded as the base of \(D_3\) and which is characterized by the species Spirifer disjunctus Sow. s. str. and Spirifer sublaevigatus V. Khalf., and an upper one, in which Retzia korovini V. Khalf. and Anathyris tschernyschewi V. Khalf. with forms close to them appear in considerable numbers; Anathyris supraphalaena Khalf. and Spirifer ales Khalf. pass through both zones. This subdivision of the supraphalaenid horizon into two zones may be presented in the following table.

Table 21

Name of forms	Zones	Supraphalaenid horizon: Sublaevigatus zone	Supraphalaenid horizon: Retzia zone
Spirifer ales Khalf.		—	—
Spirifer sublaevigatus V. Khalf.		—
Spirifer disjunctus Sow. s. str.		—
Anathyris supraphalaena n. nom.		—	—
Anathyris tschernyschewi V. Khalf.			—
Retzia korovini V. Khalf.			—

This subdivision of the supraphalaenid horizon into two zones has so far been established for a single locality—in the vicinity of the village of Yaya-Petropavlovskoe (northern margin of Kuzbass)—and it would be desirable to verify it by bed-by-bed collecting of the fauna in other areas where deposits of the supraphalaenid horizon are developed; however, the materials available at present allow one to suppose that the indicated subdivision of this horizon (at least along the margins of Kuzbass) is persistent.

In the Gorny Altai we know only deposits of the lower zone of the supraphalenian horizon; they are represented, first, by the upper part of the Malafeev Formation in the Kuyagan district. Here the supraphalenian horizon is composed below of light-gray (bluish-greenish-gray) calcareous argillite, which upward is replaced by thinly laminated dark greenish-gray clayey shales. The fauna is typical: Anathyris supraphalaena Khalf., A. peetzi Khalf., Spirifer disjunctus s. str., S. ales Khalf., Sp. mesacostalis Khalf., Douvillina dütertrii Murch., and others. In the Terektin Range equivalent deposits are represented by the upper part of the Kara-Airy Formation (p. 107), and in southeastern Altai by the same upper part of the Chibit Formation (p. 111).

In conclusion, let us note that not all Lower Frasnian deposits of the Sayan-Altai region are characterized by the supraphalenian fauna: it characterizes only the most widespread group of facies, namely the brachiopod facies, of this age. Other facies of the Lower Frasnian deposits of the Sayan-Altai region are also known to us, for example the coral facies; the fauna of this facies has not been studied; it consists mainly of representatives of the genera Alveolites, Favosites, Phillipsastraea, Cyathophyllum; locally (in the Kuzbass) the coral facies is closely connected with the brachiopod facies. In addition, we know of the goniatite facies of Lower Frasnian deposits with Beloceras and Manticoceras intumescens; it has been established in Rudny Altai and along the northwestern margin of the Kuzbass. Finally, Lower Frasnian buchiola shales with Buchiola retrostriata have recently been discovered in Rudny Altai (Khalfin, 1946a). Thus, deposits of the corresponding age in the Sayan-Altai region are represented by very diverse facies, among which the supraphalenian fauna is only the most widespread and the most studied.

In the Gorny Altai there are no Devonian marine deposits higher than the supraphalenian horizon; therefore we need not dwell here on the characterization of the fauna of the Upper Frasnian and Famennian deposits of Siberia. Let us note only that the fauna of our Upper Frasnian deposits also possesses a number of distinctive features and is likewise abundantly characterized by representatives of the genus Anathyris, among which the native group Anathyris monstrum Khalf. plays the most important role.

After acquainting ourselves with the character of the fauna distributed in the Upper Givetian and Lower Frasnian deposits of Altai, we shall continue the review begun above with the description of the Malafeev Formation.

VI. Devonian of the Korgon Range

The first reliable information on the presence in Altai of deposits with the fauna Spirifer cheehiel pertains to the Middle Devonian of the northern slope of the Korgon Range; P. P. Pilipenko, in his well-known monograph (1915, p. 96), cites forms determined by M. E. Yanishevsky from deposits which we now call the Korgon-Elov Formation: Cyathophyllum cf. caespitosum Goldf., Spirifer cheehiel Kon. and Atrypa reticularis Linn. P. P. Pilipenko’s work also gives a petrographic description of the effusives of the Devonian formations of the Korgon Range.

In 1935 I processed the fauna collected by V. A. Kuznetsov and A. S. Mitropolsky; this processing allowed me to refine the age of the Devonian deposits of the Korgon Range, which I assigned to the Upper Givetian stage, and to establish the complete similarity of the Korgon fauna to the Lebedyan fauna (Khalfin, 1935, pp. 6–8).

The Givetian deposits of the Korgon Range, according to the data of V. A. Kuznetsov and A. S. Mitropolsky, lie transgressively on a complex ...

effusive-sedimentary sequence, the age of which may also be considered Devonian, but older than Givetian. V. A. Kuznetsov and A. S. Mitropol’skii call this sequence the variegated effusive-sedimentary Devonian sequence and divide it into two parts: the lower—green, and the upper—red sequence; the “red” sequence locally lies upon the “green” sequence, being separated from the latter by a horizon of conglomerates and tuff-conglomerates, while in places it rests directly on Silurian deposits. This indicates with sufficient certainty that the “green” and “red” sequences constitute two independent formations, separated by a tectono-denudational break. The name Korgon Formation may be retained for the “red sequence,” while the “green suite” may be called the Sibiryakov Formation, after Sibiryakov Spring (basin of the headwaters of the Kumir River), where this “green sequence” is developed rather widely and completely. Finally, the Givetian deposits, which transgressively overlie the Korgon Formation, are most fully developed in the middle course of the Korgon River and its left tributary, the Elovka River; henceforth we shall call these deposits the Korgon–Elovka Formation.

Thus, in the basin of the Korgon and Kumir rivers, deposits of the following three Middle Paleozoic formations are developed:

1. The Sibiryakov Formation—a sequence varied in composition, predominantly normally sedimentary; in the lower part it consists of interbedded green and lilac argillaceous shales, green and gray-green sandstones with acid effusives, their tuffs, and tuff-breccias. Higher up, sandstones begin to predominate over the other components of the formation. Finally, in the upper part, black argillaceous and carbonaceous shales and dense sandstones are developed, alternating with flows of acid effusives (quartz and albite porphyries). The Sibiryakov Formation rests unconformably on Silurian deposits and is also unconformably overlain by the Korgon Formation. The age of the Sibiryakov Formation cannot be precisely established and is possibly Lower Devonian or even Upper Silurian.

2. The Korgon Formation is composed chiefly of effusives and their pyroclastic associates. The effusives of the Korgon Formation are represented by acid varieties (quartz porphyries and quartz albitophyres), have red and lilac colors, and possess the character of subaerial formations; their thickness is 3–4 km. The Korgon Formation rests in places on the Sibiryakov Formation, in places on Silurian deposits, and is transgressively overlain by the Korgon–Elovka Upper Givetian Formation. This determines the upper age limit of the Korgon effusive formation: it is no younger than the Upper Givetian Stage. From comparison with the effusive formations of Central Altai, we regard the most probable age of the Korgon Formation as within \(D_2^1—D_2^2\), and correlate it with the Tel’bes Formation (Table 27, p. 133).

3. The Korgon–Elovka Formation, as a basal horizon, has a hundred-meter conglomerate composed of poorly rounded pebbles consisting mainly of porphyries underlying the conglomerate; the pebble sizes reach 50–60 cm in diameter; in addition to porphyries, white marmorized limestone and pink muscovite granite are rarely encountered among the pebbles. The conglomerates are replaced by a sandy-shale sequence about 300 m thick, in which several flows of acid effusives occur; these are the famous “Korgon jaspers,” described many times in the literature; the sandstones below are red, consist of material from the effusives of the Korgon Formation, and higher up become calcareous and acquire gray-green colors. In this effusive-sedimentary sequence, the first interbeds with fauna appear. Above follows a thick (up to 2 km) sequence of dark-gray sandstones, sandy limestones, and marly shales, in co—

the latter, effusives are already absent, and there are numerous beds with abundant coral and brachiopod fauna.

The fauna of the Korgon–Elovka Formation is characterized by the predominant development of coelenterates and brachiopods; the latter form a most typical complex of givetian fauna:

Chonetes coronata Hall
Productella subaculeata (Murch.)
Productella spinulicosta Hall
Leptaena rhomboidalis (Wilck.)
Stropheodonta pseudasella n. nom.
Schellwienella umbraculum (Schloth.)
Isorthis sibirica (Khalf.)
Aulacella eifeliensis (Vern.)
Schizophoria striatula (Schloth.)
Uncinulus korovini Khalf.
Spirifer cheehiel Kon.
Spirifer cheehiel Kon. var. alata Khalf.
Spirifer martianoffi Stuck.
Spirifer cabedanus Vern. et Arch.
Spirifer mesacostalis Hall
Cyrtina heteroclita (Defr.) var. intermedia Oehl.
Athyris concentrica (Buch)
Athyris fultonensis Swall.
Athyris circularis Khalf.
Atrypa reticularis (Linn.)
Atrypa desquamata Sow.
Conocardium cuneus Hall
Cypricardinia lima Schnur

The above list of fauna proves beyond doubt that the Korgon–Elovka Formation is stratigraphically equivalent to the Givetian part of the Malaya Formation. In facies terms, however, there is a considerable difference between them: the Malaya Formation, as already mentioned, is composed almost exclusively of argillaceous shales that do not react to HCl, whereas in the Korgon–Elovka Formation sandstones, calcareous-marly rocks, and benthogenic limestones predominate.

This difference in lithological composition is substantially supplemented by differences in the fauna. Of greatest interest is the abundance of coelenterates in the Korgon Devonian (in particular, colonial forms), whereas in the Middle Devonian of Malafeev Klyuch colonial coelenterates are completely absent, and only in the bed with Anathyris supraphalaena are solitary corals encountered as very rare specimens. Significant differences are also present in the composition of the brachiopod and pelecypod fauna of the Devonian deposits of the localities being compared.

The cited differences in lithological and faunal composition quite clearly indicate that in the Kuyagan district we have a deeper-water facies of the Middle Devonian than on the Korgon. We shall have to return to this circumstance below.

The Korgon–Elovka Formation shows a considerably greater similarity with the Lebedyan Formation, developed near the village of Lebedyanskoye (Anzhero-Sudzhensk district) on the northern margin of the Kuzbass. This applies both to the lithological composition and, especially, to the fauna. In addition to the fact that the Lebedyan Devonian is likewise rich in coelenterates and brachiopods and poor in mollusks and trilobites, there is a striking similarity (perhaps even

complete identity) of the brachiopod fauna of the Lebedyan and Korgon Devonian. Almost all brachiopods from the above list of the Korgon fauna occur in the Lebedyan Devonian, whereas many of them are absent from the coeval and geographically closer fauna of the Malafeev Formation.

Having emphasized the close similarity of the two faunas, I must also note the differences that exist between them. The circumstance that in the Lebedyan Devonian we know 75 species varieties of brachiopods, and in the Korgon–Elovka Formation 21, of course, still cannot serve to distinguish the Lebedyan fauna from the Korgon fauna: the latter has simply been studied less well and still awaits detailed collecting. An essential difference is the abundance, in some beds of the Lebedyan Devonian, of massive stromatoporoids, not characteristic of the Korgon \(D_3\). Comparing this circumstance with the more variegated lithological composition of the Lebedyan Devonian, with the more frequent alternation in it of clayey-marly, sandstone, and limestone beds, we must conclude that the Lebedyan Devonian, facies-wise close to the Korgon, represents deposits of an even shallower-water and less stable basin.

Thus, in the three localities being compared (Malafeev Klyuch, Korgon, Lebedyanka) we have three different facies of one and the same stratigraphic horizon:

1) Malafeev facies: lithological composition—a uniform clayey-shale sequence; fauna—abundance of Spirifer cheehiel var. altaica and Spirifer mucronatus, absence of coelenterates;

2) Korgon facies: calcareous sandstones and shales and coral limestones, in the lower part—interbedding with acid effusives; fauna—abundance of Spirifer cheehiel typ. et var. alata, Spirifer martianoffi, Leptaena rhomboidalis, coelenterates;

3) Lebedyan facies: variegated alternation of marly shales and sandstones, marls and limestones, coral and stromatoporoid limestones; fauna—abundance and diversity of spirifers of the group Spirifer cheehiel, various brachiopods, coelenterates, stromatoporoids.

For clarity, we present the comparison of these facies in the form of a table:

Table 22

Facies	Coral limestones	Stromatoporoid limestones	Effusives	Group Spirifer cheehiel	Spirifer martianoffi	Spirifer mucronatus	Productella spinulicosta	Leptaena rhomboidalis	Schellwienella umbraculum	Isorthis sibirica
Malafeev	−	−	−	+	−	+	+	−	−	+
Korgon	+	−	+	+	+	−	+	+	+	+
Lebedyan	+	+	−	+	−¹)	−	+	+	+	+

From this comparison we see that the facies being compared are linked by certain common forms—the group Spirifer cheehiel, Productella spinulicosta, Isorthis sibirica; it is obvious that these forms are the most eurybathic, since the facies differences of the formations being compared are determined primarily by the depth of the basin in which they were formed: the Lebedyan facies is the most nearshore, the Korgon somewhat deeper-water, and, finally, the Malafeev facies is a facies of the open sea. Each of them is characterized by certain

¹) One specimen was found, belonging to a special variety.

certain organic forms, whose distribution is apparently determined mainly by their stenobathic character. Thus, Spirifer mucronatus evidently preferred to settle in the deeper zones of the Upper Givetian basin; Spirifer martianoffi chose shallower-water areas, though not the most coastal ones, where massive bryozoans lived in abundance. On the whole, the Korgon and Lebedyan facies are closer to one another and differ substantially from the Malafeev facies; this is indicated both by their more similar lithological composition and by the large number of forms they have in common.

In the section along the Korgon, the Frasnian stage crowning the Devonian rocks of the Malafeev key was not found. This circumstance, it seems to me, we may rightly correlate with the fact that the rocks of the Korgon–Elovka formation are shallower-water deposits than the rocks of the Malafeev formation and, consequently, the Upper Devonian regression freed the area of the present Korgon from beneath sea level earlier than the Kuyagan area.

VII. The Devonian of Central Altai

In Central Altai, Devonian deposits have been preserved in separate grabens among older, predominantly Silurian, deposits. The Devonian deposits of two grabens have been studied most fully (Fig. 13):

Fig. 13. Principal localities of Devonian deposits of Central and Southeastern Altai. K—Kurota graben; B—Belgabash graben; Ka—Kara-Irtysh formation; At—Aktash formation; Chu—Chagan-Uzun formation; Kg—Karaem formation; Ak—Akkai member of the Chibit formation; Bu—Bugusuyas member of the Chibit formation; Yu—Yustyd formation.

a) the Kurota graben, which is elongated in a meridional direction from the area of the village of Ongudai to the area of the village of Shebalino, and

b) the Belgebash graben, which is situated to the southeast, in the lower course of the Chuya River, in the area of the village of Chibit.

In both of these grabens there are Upper Givetian deposits of the Malafeevo facies with a brachiopod fauna; in both grabens they unconformably overlie effusive-sedimentary formations that are also Devonian in age.

Somewhat apart stand the poorly studied Devonian deposits of the Terektin Range: in their facies type and in the presence not only of Upper Givetian but also of Lower Efranian deposits, they differ from the Belgebash and Kurota Devonian and approach the Devonian of the southeastern part of the Altai.

1. Devonian of the Belgebash Graben

The complex Belgebash graben is crossed by the Chuya River (a right tributary of the Katun) at a distance of about 45 km from the mouth of the latter; it is elongated in a meridional direction and along the Chuya River has a width of 15 km; the village of Chibit is situated at the eastern margin of the graben.

The composition and structure of the Belgebash Devonian were most fully characterized by Yu. A. Kuznetsov (1939), who determined its stratigraphy, facies character, bedding, and relationship to the surrounding formations. According to this author, the Devonian deposits of the Belgebash graben are gathered into tight folds of northwestern strike and are squeezed among more ancient (Silurian) formations, with which they have tectonic boundaries. The Devonian forms three synclinal folds, separated by anticlinal folds complicated by disjunctives, in the cores of which Silurian rocks crop out.

The section of the eastern (Belgebash) syncline was studied in greatest detail by Yu. A. Kuznetsov; from top to bottom it is as follows:

Lithology	Thickness
Black, weakly bedded limestones with interbeds of black shales and fine-grained sandstones	150–180 m
Coarse-grained sandstone, consisting of fragments of acidic effusives	1 m
Interbedding of dark-gray sandstones and limestones with Pachypora	15 m
Dark-gray platy limestones with a fauna of brachiopods, bryozoans, and tabulates (Spirifer mucronatus, Spirifer cf. martianoffi, Athyris concentrica, Hemitrypa devonica, Pachypora cervicornis var., etc.)	10.5 m
Dark-gray limestones with Hysterolites cheehiei	20 m
Black clayey calcareous shales	20 m
Gray-green sandstones and marls	25 m
Barren black and dark-gray limestones	120 m
Green marl	40 m
Gray coarse-grained sandstone	20 m
Lilac shales, sandstones, conglomerates, limestones	110 m
Foliated felsites and quartz porphyries (a disturbance is possible here)	50 m
Barren gray limestones	20 m
Dark-lilac shales with interbeds of lilac sandstones and limestones	360 m
Dark-lilac aphanites and green and lilac tuffs and agglomerates	150 m
Dark-gray and greenish-gray limestones and marls	300 m
Crumpled green and lilac felsites and felsite breccias	300 m

Tectonic contact with the Chuya Upper Silurian formation. Total thickness of the deposits, 1800 m.

Yu. A. Kuznetsov points to the presence in this section of two different complexes: the lower complex—effusives and variegated barren shales, sandstones, marls, and limestones interbedded with them; thickness about 1300 m; the deposits represent terrestrial eruptions and continental and lagoonal sediments; the upper complex—black and

gray limestones, shales, and sandstones with the usual Givetian fauna of the Upper Givetian stage; thickness—about 450 m.

Between the lower and upper complexes Yu. A. Kuznetsov (table 1, p. 87) established the presence of an erosional break; i.e., within the Belgébash Devonian we quite clearly distinguish two independent formations: the Upper Givetian, which it is convenient to call the Belgébash Formation, and a more ancient, effusive-sedimentary one, for which the name Belgébash–Chuya Formation may be proposed.

Along the strike to the northwest the composition of the Belgébash Formation changes rapidly: here it is represented mainly by gray shales with interbeds of limestones; “the facies conditions of sediment accumulation were very unstable” (Yu. Kuznetsov, 1939, p. 39).

In two other synclines of the Belgébash Devonian the composition of the rocks is different and, schematically, is represented as follows:

above—a thick unit of black and gray clayey shales;
in the middle part—gray and black calcareous-clayey shales and clayey limestones;
below—acid effusives, occurring in a diagenetic phase, interbedded with tuffs and red sandstones and shales.

In the upper shale unit a coral reef has been found with Phillipsastraea verneuili E. H., Spongophyllum (Endophyllum?) altaicum n. sp. (Radugin), Zaphrentis sp. In the middle limestone-clayey unit bryozoans and corals have been encountered: Striatopora altaica n. sp. (Radugin), Pachypora cervicornis var., Coenites crateroides n. sp. (Rad.), Syringopora of Middle Devonian type, Clathrocoilona (?) altaica n. sp. (Rad.). According to K. V. Radugin, all this fauna is of Middle Devonian age.

At present it is impossible with complete certainty to correlate these deposits with the deposits of the Belgébash syncline; the identical scheme of the sections—acid effusives below, normal marine rocks above—may speak in favor of the assumption that the lower effusive part of the deposits of the western synclines belongs to the Belgébash–Chuya Formation, and the upper, limestone-shale part to the Belgébash Formation. With such a correlation (accepted by Yu. A. Kuznetsov), within the deposits of the western synclines the upper part of the Belgébash–Chuya Formation, consisting of variegated shales, drops out. Yu. A. Kuznetsov believes that this is explained by deposition of the rocks of the western synclines in the open sea, whereas the deposits of the Belgébash syncline (except for the Upper Givetian) are lagoonal-continental; these differences also explain the different character of the effusives of the Belgébash–Chuya Formation: in the western synclines they have the character of green subaquatic formations, in the Belgébash syncline of lilac-red terrestrial ones. Such a correlation may be accepted as a first approximation, bearing in mind that further, more detailed study of the deposits of the western synclines may introduce substantial corrections into this comparison: in favor of this, for example, is the absence in the upper limestone-shale unit of the western synclines of Givetian fauna, which is abundantly represented in the Belgébash syncline; the possibility is not excluded that the deposits of the western synclines are of another age and belong to other formations.

The deposits of the Belgébash syncline are the most studied, a detailed section of which was given above. A detailed characterization of the Belgébash Formation was also given by V. P. Nekhoroshev (1932, pp. 62–64) under the name of the Berdybash marine beds (ib., p. 83), but in the interpretation of the section of these deposits there are profound disagreements between Yu. A. Kuznetsov and V. P. Nekhoroshev. Since the more recent investigations of Yu. A. Kuznetsov are also more detailed, in the views of V. P. Nekhoroshev, who observed the Belgébash Devonian only in

during the route investigations of the Altai, one might not have dwelt on it; however, V. P. Nekhoroshev supports his views on the character of the section that interests us by an analysis of the fauna, determined by him personally and by N. L. Bublichenko. Since my conclusions on the age of the fauna from various points of the Bel’gebash section diverge from the conclusions of V. P. Nekhoroshev, I must dwell on the interpretation of the Bel’gebash section proposed by V. P. Nekhoroshev.

Yu. A. Kuznetsov regards the Bel’gebash section as a large synclinal fold, complicated in its middle part by several folds of the second order. This construction is substantiated, in particular, by the regular repetition in the Bel’gebash section of beds with Spirifer cheehiel Kon. and beds with Spirifer mucronatus Conr., the stratigraphic relations between which were established by me in northwestern Altai (see above—the Malafeev Formation). The interpretation of the Bel’gebash deposits given by Yu. A. Kuznetsov is illustrated by his ideal section (Kuznetsov, 1939, p. 40), which is reproduced in Fig. 14.

Ideal section of the Middle Devonian at the mouth of the Bel’gebash River

Scale: 0–500–1000 m

Legend:

1. Shales of the green-violet formation
2. Effusive rocks
3. Gray and green-gray limestones and marls
4. Lilac shales and sandstones
5. Dark-gray dark limestones
6. Horizon with Hypothyris cheehiel
7. Horizon with Spirifer mucronatus
8. Black limestones with interbeds of shales and sandstones

Fig. 14. Copy after Yu. A. Kuznetsov (1939, p. 40)

V. P. Nekhoroshev, having noted the symmetrical arrangement of beds of similar lithological composition, nevertheless sees certain differences in the composition of the fauna of the western and eastern parts of the section, on the basis of which he comes to the conclusion that the Bel’gebash deposits form not an isoclinal fold, but “one continuous stratigraphic section” (Nekhoroshev, 1932, p. 64). V. P. Nekhoroshev divides this section into three parts: the upper—500 m thick, the middle—500 m thick, and the lower—300 m thick; these three parts are characterized by different faunas, and the total thickness of the “Berdybas marine beds” is determined as 1300 m.

As already indicated above, the “Berdybas marine beds” of V. P. Nekhoroshev correspond to the upper Bel’gebash complex of Yu. A. Kuznetsov, for which the latter assumes a thickness of about 450 m. Comparison of the sections given by these two authors is difficult, since the lithological composition of the section cited by them differs: according to Yu. A. Kuznetsov’s data, limestones predominate in the upper Bel’gebash complex in the section near the Chui River; according to V. P. Nekhoroshev’s data, the same section is characterized by the predominant development of sandy-argillaceous and argillaceous shales. Probably this discrepancy is to some extent explained by the facies instability of the Bel’gebash Devonian deposits noted by Yu. A. Kuznetsov; the presence of reference horizons characterized faunistically nevertheless makes it possible to compare the views of V. P. Nekhoroshev and Yu. A. Kuznetsov. This comparison is given in Fig. 15, in which, according to the data of Yu. A. Kuznetsov (1939)

pp. 37–39) part of the Belgebash section, and the position of the horizons distinguished by V. P. Nekhoroshev is indicated.

Further analysis of the relationships between the various parts of the Belgebash section must be preceded by a presentation of the data relating to the fauna of the Belgebash Formation. This fauna is abundant and varied; it belongs chiefly to brachiopods, bryozoans, and coelenterates. I studied the brachiopods from the collections of Yu. A. Kuznetsov.

Fig. 15. Schematic correlation of the Devonian horizons of the Belgebash graben according to Yu. A. Kuznetsov and V. P. Nekhoroshev: m—horizon with Spirifer mucronatus, c—horizon with Spirifer cheehiel (after Yu. A. Kuznetsov); n—lower, sr—middle, v—upper horizons according to V. P. Nekhoroshev.

The brachiopods of the Belgebash Formation, which I had for determination, are on the whole poorly preserved, owing to their considerable deformation; their determination in a number of cases presents great difficulties, but it is greatly facilitated by the possibility of direct comparison of the organic remains of the Belgebash Formation with the well-studied organic remains of the Malafeev Formation, analogous in stratigraphic and facies respects. Among the brachiopods collected by Yu. A. Kuznetsov, I have identified:

Chonetes hemisphaerica Hall
Productella spinulicosta Hall
Stropheodonta pseudassella n. nom.
Schellwienella umbraculum (Schl.)
Aulacella eifeliensis (Vern.)
Isorthis sibirica (Khalf.)
Spirifer cheehiel Kon.
Spirifer cheehiel Kon. var. altaica Khalf.
Spirifer mucronatus Conr.
Spirifer cf. martianoffi Stuck.
Spirifer ex gr. Sp. bouchardi Murch.
Spirifer cf. tenticulum Vern.
Cyrtina heteroclita (Defr.) var. intermedia Oehl.
Athyris concentrica Buch
Athyris circularis Khalf.
Athyris glassi Dav.
Retzia lopatini Stuck.
Atrypa reticularis Linn.

This list of brachiopods of the Belgebash Formation is quite sufficient for precisely establishing its stratigraphic position and facies type, and the bed-by-bed character of the faunal collections made by Yu. A. Kuznetsov makes it possible to establish the nature of the structure formed by the Belgebash Formation and the exact correlation of its horizons with the horizons of the Malafeev Formation.

The stratigraphic position of the Belgebash Formation is determined by the diagnostic Upper Givetian forms: Spirifer cheehiel typ. et var.,

Spirifer mucronatus, Isorthis sibirica. No more ancient elements have been found in this fauna, including the form that might correspond to that cited by V. P. Nekhoroshev under the name Spirifer cf. sulcatus Barrande; on the basis of the above list of forms, I accept that in the fauna of the Belgebash Formation there are not only no Lower Devonian forms, but, in general, this formation contains no horizons older than the Upper Givetian.¹ Likewise, apparently, Upper Devonian deposits are also absent from this formation: isolated specimens of spirifers of the Spirifer disjunctus group (in our list—Spirifer cf. tenticulum) appear, as was noted above (p. 81), in the horizon with Spirifer mucronatus of the Malafeev Formation, which still belongs to the Middle Devonian. Those black and dark-gray limestones that lie above the bed with Spirifer mucronatus and are exposed in the hinge part of the Belgebash syncline (Fig. 14) might belong to the lower part of the Upper Devonian. However, no Upper Devonian fauna has been found in them; judging from the section of the Malafeev Formation, the horizon with Spirifer mucronatus may have a fairly considerable thickness and, probably, in the Belgebash syncline it also includes these limestones. Thus, we arrive at the conclusion that the Belgebash Formation corresponds to the lower (Middle Devonian) part of the Malafeev Formation.

A bed-by-bed study of the fauna made it possible to establish that, in the Belgebash syncline, beds with Spirifer cheehiel and Spirifer mucronatus are repeatedly and regularly repeated (Fig. 15). Since their stratigraphic relationships were established in the Kuyagan district (p. 77), it appeared possible to establish the presence and character of folds, formed—

The fossil fauna of Western Siberia is distinctive and has many peculiarities; in particular, groups and forms are not infrequently encountered in it that occupy a different stratigraphic position from that which they occupy in other countries (for example, see above—on the superstitid elements of the supra-Frasnian fauna—p. 88). In the article published in the first issue of Izvestiya of the West Siberian Branch of the Academy of Sciences of the USSR (Khalfin, 1946), I discuss these questions in detail and give many examples showing the unfortunate consequences to which hasty stratigraphic conclusions lead when they are based on approximate and incomplete determinations of the Siberian fossil fauna. But if A. N. Churakov’s assertion concerning the presence in central Altai of a faunistically characterized Lower Devonian should be treated with great caution, then still more perplexing is this author’s assertion that deposits which V. P. Nekhoroshev (1932) called the “Berdy-Bash marine beds,” and Yu. A. Kuznetsov (1939) “the upper complex of the Belgebash Devonian,” belong to the Lower Devonian. Such an assertion is all the more surprising because this very coral (Thamnophyllum sp.) was found not in the eastern syncline (see above, p. 95), but in one of the western ones (see above, p. 96)—“near the mouth of the Yarbalýk”; moreover, “the conditions of occurrence of this suite were not studied by us” (Churakov, c. l., p. 137). Thus, the data presented by A. N. Churakov permit only raising the question of the possible presence of the Lower Devonian in one of the western synclines of the Belgebash graben. As for the Belgebash Formation, i.e., the deposits of the eastern syncline, whose fauna A. N. Churakov attempts to analyze, it is necessary to say once again the following about them: after I studied the fauna collected in them by Yu. A. Kuznetsov, and my conclusion was used and cited in the work of Yu. A. Kuznetsov (1939), the question of the Upper Givetian age of these deposits was decided definitively, and after this “all investigators assign the sediments of this sea to the Givetian stage of the Middle Devonian” (Churakov, c. l., p. 157), and only A. N. Churakov, “not being himself a paleontologist” (c. l., p. 137) and, as is shown by all his reflections on this question, not being at all familiar with the Devonian fauna of Siberia, adheres to a different point of view.

studied as the Belgebash Formation. In particular, it has been shown that the “lower” and “upper” horizons of V. P. Nekhoroshev are the limbs of the principal synclinal fold of the Belgebash section (Fig. 15).

The presence in the Belgebash Formation, alongside the Spirifer cheehiel group, of the species Spirifer mucronatus, with a definite relationship of their stratigraphic positions in this formation, emphasizes the great facies similarity between the Belgebash and Malafeev formations. I am inclined to assign them to a single (Malafeev) facies, although there are certain minor differences between them. These differences are as follows: the Malafeev Formation (in its Middle Devonian part) is composed of a monotonous clayey-slate sequence, whereas in the Belgebash Formation limestones play a significant role, especially in the southeastern part of the Belgebash graben. The interbedding of slates and limestones, and the presence of coelenterates in some limestone beds, indicate that the Belgebash Formation was deposited in a somewhat shallower and less stable part of the Upper Givetian basin than the Malafeev Formation. Related to this is also the occurrence, in some beds of the Belgebash Formation, of such brachiopods as Schelwienella umbraculum and Leptaena rhomboidalis (reported by V. P. Nekhoroshev), which characterize shallower-water facies (than the Malafeev) of the Altaian \(D_2^3\) (p. 93). However, the presence in the fauna of this formation of Spirifer mucronatus, not encountered in the shallow-water deposits of the Korgon and Lebedyan facies, brings the Belgebash Formation closer to the Malafeev. As we shall see later (p. 130), all these facies differences and similarities are explained by the character of the distribution of the Upper Givetian basin of Altai. Thus, the following characterization of the Belgebash Formation may be given. It is a normally sedimentary sequence consisting of an alternation of dark-gray slates and limestones; along the strike, the quantitative relationships between slates and limestones undergo considerable fluctuations; the formation is characterized by a Chudov fauna, permitting the recognition of a horizon with Sp. cheehiel and a horizon with Sp. mucronatus; in facies terms the Belgebash Formation is close to the Malafeev, being somewhat shallower-water.

The thickness of the Belgebash Formation, according to Yu. A. Kuznetsov, is only 450 m, i.e., considerably less than the thickness of the Malafeev Formation. It seems to me that this is a consequence of denudation of the upper part of the Belgebash Formation, and that its true thickness was probably more considerable (apart from the greater thickness of the Malafeev Formation, we are led to think so also by the considerably greater thickness of the Upper Givetian deposits of the neighboring Kurota graben).

The Upper Givetian age of the Belgebash Formation determines the upper age limit of the effusive-continental sequence of the Belgebash–Chuya Formation; in its composition and position it corresponds to the Korgon Formation (p. 91) and can be correlated with it.

2. Devonian of the Kurota Graben

The left bank of the Katun between the rivers Ursul and Sema for a long time was one of the least studied regions of Altai. V. P. Nekhoroshev’s journey scarcely touched this region, and on the schematic geological map of Altai compiled by this author (1932), undivided Lower Paleozoic (\(Cm + S\)) and Upper Silurian are shown here. K. V. Radugin deserves the credit for the detailed study of this region; to

unfortunately, the results of his investigations still remain unpublished.^1)

Within the indicated area, K. V. Radugin established the widespread development of Devonian deposits forming a tectonic wedge, named by K. V. Radugin the Kurota graben after the Kurota River, a left tributary of the Ursul River. This graben (fig. 13) has the outlines of a long wedge of NNW strike; in the south it embraces the middle course of the Ursul River for a distance of 30 km; in the north it wedges out on the Sema River above the mouth of the Chernaya Mayota River; the extent of the graben is more than 70 km; the southern boundary of the graben has not been established. The Devonian deposits of the Kurota graben constitute a thick and complex effusive-sedimentary sequence; at various points of the graben a fauna of brachiopods and coelenterates was found, which, unfortunately, has been studied quite inadequately; according to preliminary determinations these faunal data “indicate the Middle Devonian age of the entire sequence” (Radugin). Later K. V. Radugin subdivided the Devonian deposits of the Kurota graben in great detail, establishing in it, in particular, the presence of analogues of the effusive-continental formations of the Telbes district of Gornaya Shoria. Finally, detailed investigations by Yu. A. Kuznetsov (1939) covered the southern part of the graben; this author described the Devonian effusives and diabases and specified the relationships between the formations developed along the margins of the graben.

As the observations of K. V. Radugin and Yu. A. Kuznetsov have shown, the Kurota graben is of exceptional interest for the study of the Devonian of the Altai; over the considerable area occupied by this graben, several different continental and marine Devonian formations are developed, the relationships between which still cannot by any means be regarded as definitively established. The probable presence in this graben of faunistically characterized Eifelian deposits (p. 79), the presence in it of effusive-continental formations analogous to those of Gornaya Shoria, and also the presence of intrusions of Telbes age—are the most important elements of the geology of this graben. The characterization of the formations developed in it is given below on the basis of the materials of K. V. Radugin and Yu. A. Kuznetsov.

K. V. Radugin distinguishes the following formations in the composition of the graben (from top to bottom):

Kurota Formation;
Antropovka and Abramovka formations;
Middle Telbes Formation;
Ongudai Formation.

The formations are separated by breaks corresponding to phases of tectogenesis established in Gornaya Shoria; intrusive volcanism is associated with some of these phases (p. 105). The scheme presented does not include the deposits, also established by K. V. Radugin, of a formation containing the Tytkeskene horizon, apparently of Eifelian age (p. 79).

We shall begin the review of the Devonian formations of the Kurota graben with the oldest—

^1) In the collection Gorny Altai (Proceedings of the Oirot Complex Expedition of the Academy of Sciences of the USSR, vol. 1), an article by K. V. Radugin, “Geological Sketch of the Chemal Sheet,” was published, containing a description of the Devonian of the Kurota graben; I used the materials of K. V. Radugin and Yu. A. Kuznetsov (1939) in characterizing the Devonian deposits of this graben. In K. V. Radugin’s article the description of the Devonian of the Kurota graben is, naturally, more complete (in particular with respect to the red-colored formations and intrusions), but my interpretation of these materials is somewhat different. Thus, K. V. Radugin assigns the Tytkeskene horizon to the Kurota Formation, whereas it seems to me that it is considerably older; the subaqueous character of the effusives of the Kurota graben and the presence among them of interbeds with marine fauna substantially distinguish them from the Middle Telbes sequence of Gornaya Shoria, etc.

which are situated along the margins of the graben (and partly beyond the limits of the latter).

a) Karakudyur Formation

This formation was characterized in detail by Yu. A. Kuznetsov (1939); it forms a narrow belt along the eastern margin of the Kurota graben (in its southern part), but, without reaching the Ursul River, turns eastward at a right angle, crosses the Katun River as a narrow strip, and rapidly wedges out on the right bank of the latter. The formation is a variegated continental sequence 0.5 to 1 km thick, formed through the destruction of local rocks of Silurian and Cambrian age. At the base of the Karakudyur Formation lies a horizon of gray conglomerates; above follows an interbedding of red, lilac, and green sandstones and conglomerates; still higher—an interbedding of green and red clayey shales, to which gray and black sandstones and shales are locally added. The Karakudyur Formation forms simple and fairly gentle folds, but, being squeezed between steep reverse faults, it shows intense dislocation near the latter.

The age of the Karakudyur Formation is not precisely established: it lies transgressively on Lower Silurian formations and contains in its conglomerates pebbles of already phyllitized shales of the latter; on the other hand, it is cut by dikes of effusives of the Ongudai Formation (see below). K. V. Radugin considers this formation older than the Chui Formation \(S_2\). Yu. A. Kuznetsov (1939) notes the similarity of the Karakudyur Formation to the Sibiryachikha Formation of the Korgon Range (p. 91); it need only be observed that the latter contains acid effusives, whereas the Karakudyur Formation has no pyroclastic components.

Distribution: in addition to the Kurota graben, the Karakudyur Formation has been encountered along the right margin of the Belgebash graben (along the Chuya River, above the mouth of the Chibit River). In addition, this formation is developed on the watersheds of the Mek and Yarlu-Airy rivers and of the Chibit and Korumdu-Airy rivers (Kuznetsov, 1939, p. 35).

b) Ongudai Formation

This formation is developed along the margins of the Kurota graben in its southern part and accompanies the Karakudyur Formation in its eastern (Katun) branch. In this eastern part, along the Kaincha River (a left tributary of the Katun), Yu. A. Kuznetsov observed the occurrence of the Ongudai Formation in the core of a syncline complicated by disjunctives, in whose limbs occur rocks of the Karakudyur Formation. On the other hand, the Ongudai Formation is cut by dikes of quartz porphyries, which are feeder channels of Devonian intrusions.

The Ongudai Formation is mainly pyrogenic, and K. V. Radugin deserves credit for distinguishing these effusives from the Cambrian and Kurota ones. The petrographic composition of the Ongudai effusives, their distribution, and their mode of occurrence were studied in detail by Yu. A. Kuznetsov.

The effusives of the Ongudai Formation are of intermediate basicity; they are green and lilac porphyrites, at times with abundant phenocrysts of pyroxene or only plagioclase, more rarely amygdaloidal and aphanitic; they always display strong fissility. These effusives represent subaerial eruptions (Kuznetsov, 1939, p. 35), the flows of which are interbedded with sandstones, conglomerates, and shales—

the deposits, but these clastic formations are of subordinate importance; their green-lilac colors are characteristic.

There is no information on the thickness of the Ongudai Formation. K. V. Radugin provisionally correlates the Ongudai Formation with the lower part of the Telbes Formation of Gornaya Shoria. However, despite all the variability that characterizes pyroclastic strata, we can establish certain differences between the Ongudai Formation and the lower suite of the Telbes Formation: 1) in the latter, clastic components predominate, whereas in the former they play an entirely subordinate role; 2) the effusives of the Ongudai Formation are more basic. I am more inclined to agree with the opinion of Yu. A. Kuznetsov (1939, p. 36), who noted the similarity of the Ongudai Formation to the effusive part of the Lower Devonian Kuyagan Formation.

c) Effusive and continental deposits of the Kurota graben

The Karagudzhur and Ongudai formations are developed partly along the margins of the Kurota graben and partly beyond its limits; within the graben itself there occurs a complex assemblage of effusive, continental, and marine deposits, which Yu. A. Kuznetsov (1939) regarded as a single effusive-sedimentary sequence, while K. V. Radugin divided it into a number of independent formations. Leaving aside for the time being the reliably marine Devonian of the Kurota graben, let us consider the effusive and continental deposits. They are represented, first, by a thick (up to 4 km) sequence consisting essentially of acidic effusives: felsites, quartz porphyries, more rarely felsite-porphyries and quartz albitophyres; porphyrites are very rare (Kuznetsov, 1939, p. 42). Subordinate to these effusives are tuffaceous sandstones and shales, among which, locally (on the Chue River, near the mouth of the Tuenta River), beds of marly limestones with marine fauna occur (Pachypora, Favosites cf. forbesi).

K. V. Radugin sees in this effusive sequence an analogue of the middle part of the Telbes Formation, in which he (1936, p. 58) observed, in Gornaya Shoria along the Mrassu River, the development of acidic effusives. It should be noted that the Gornaya Shoria effusives with which K. V. Radugin correlates the effusives of the Kurota graben have a thickness ten times smaller and are of a different character: the Telbes Formation in Gornaya Shoria consists of purely continental formations, whereas the Kurota effusives, according to Yu. A. Kuznetsov, who studied them, represent “essentially submarine eruptions” (Kuznetsov, s. l., p. 44). The presence, noted above, of interbeds with marine fauna within the Kurota effusive sequence also speaks in favor of this. Only study of the latter, as well as clarification of the relationships between the Kurota effusive sequence and the Eifelian deposits encountered in the northern part of the graben (see below), will make it possible to determine precisely the age of the Kurota effusive formation and to parallelize it with the deposits of other regions. For the reasons set forth above, I do not consider it convenient to retain for this formation the name “Middle Telbes Formation” proposed by K. V. Radugin; and, since the term Kurota Formation was assigned by K. V. Radugin to Upper Givetian marine deposits, the name Kurota–Ursul Formation may be proposed for the pyroclastic sequence under consideration.

Thus, by the name Kurota–Ursul Formation we understand a thick (up to 4 km), essentially pyroclastic sequence composed of acidic effusives, to which very insignificant ...

a significant role is played by clastic rocks, but among the latter there are locally encountered argillaceous limestones with a still unstudied fauna of coelenterates.

K. V. Radugin established, within the Kurota graben, along the left bank of the Kurota River, a special continental formation, which he tentatively correlates with the Antropovo Formation of Gornaya Shoria. This formation has at its base a conglomerate, the pebbles of which consist of effusives of the Kurota–Ursul Formation; above follows an interbedding of gray sandstones and red shales, and still higher—stratified porphyrites and their tuffs. The thickness of this formation, which we shall designate as the Antropovo (?) Formation, is measured at only a few meters or tens of meters, but in the pebbles of its basal horizon K. V. Radugin observed relict tectonostructures and red weathering crusts. Thus, the presence has been established of a break separating the Antropovo (?) Formation from the Kurota–Ursul Formation. K. V. Radugin has indications of the presence in the Kurota graben also of the Abramovo (?) Formation in its dike facies.

г) Eifelian marine formation of the Kurota graben

As was already noted above, in the northern part of the Kurota graben, near its eastern margin, in the upper reaches of the Tytkesken River, K. V. Radugin discovered a limestone with coral fauna, apparently of Eifelian age (p. 79). The composition of the formation into which the Tytkesken horizon enters has not been established, nor has the relation of this formation to those described above; it is known only that they are certainly older than the Upper Givetian Kurota Formation (see below), since, in the opinion of K. V. Radugin, the coelenterates of the Tytkesken horizon are probably Lower Eifelian. At present it is hardly possible to determine precisely the position of the Tytkesken horizon in the stratigraphic column of the Kurota graben. If it is accepted that the Kurota–Ursul and Antropovo (?) formations correspond to the Telbes group of effusive-continental deposits of Gornaya Shoria, we shall have to regard the formation of the Tytkesken horizon as more ancient, corresponding to some extent to the Karachkino Formation of the Kuzbass (Usov, 1936, table II). At the same time there is no need to place the Kurota–Ursul Formation entirely in the Givetian Stage: it may prove to be partly or wholly Eifelian (if, of course, the Lower Eifelian age of the Tytkesken fauna is confirmed). In assigning the indicated place to the Tytkesken horizon in the section of the Kurota Devonian, we are fully aware that a detailed study of its fauna, as well as of that fauna which is encountered here and there in the Belgebash–Chuya Formation, may substantially alter the stratigraphic relations between them.

д) Kurota Formation

Within the Kurota graben, marine normally sedimentary deposits are widely developed; they are represented chiefly by argillaceous shales, which are interbedded with limestones, sandstones, and intraformational conglomerates. These deposits rest unconformably on the Kurota–Ursul Formation and are characterized by the brachiopod fauna usual for Upper Givetian deposits of Siberia. This fauna has been found at various points of the Kurota graben and has not yet been subjected to detailed treatment. But it contains such forms as Spirifer cheehiel typ. et var. altaica, Spirifer mucronatus, Productella spinulicosta, and others, constituting the usual fauna already considered by us more than once.

association of forms. The composition of the fauna and the predominantly argillaceous-schist character of the Kurota Formation indicate its equivalence, in stratigraphic and facial respects, to the lower part of the Malofeyevka Formation. But, as in comparing the latter with the Belgebash Formation (p. 100), we must note here that that part of the Upper Zivetian basin in which the rocks of the Kurota Formation were deposited was less stable than the more northern (Kuyagan) part; this is indicated by the presence, within the Kurota Formation, of interbeds of sandstones and conglomerates. The latter, moreover, indicate the presence nearby of a mountainous shore, which, during the deposition of the rocks of the Kurota Formation, at times underwent uplift and subsidence: the former were accompanied by the transport into the neighboring marine basin of coarse-clastic material, which formed interbeds of conglomerates amid the argillaceous-schist sequence of this formation. These pulsations were probably reflections of those tectonic movements that took place during the formation of the complex sequence of the Kurota graben and were accompanied at times not only by effusive but also by intrusive volcanic activity.

e) Devonian intrusions of the Kurota graben

In the work of Yu. A. Kuznetsov (1939) there are interesting data on the principal intrusive rocks of the Kurota graben, which are of Devonian age; these are diabases, forming numerous, sometimes very thick (up to 300 m) sills lying among the clay shales of the Kurota Formation and dislocated conformably with the latter: “the diabase sills were folded into modern folds together with the enclosing sedimentary sequence” (Kuznetsov, op. cit., p. 55). In addition to diabases, acid intrusives also occur within the Kurota graben: they are represented by alkaline granites, constituting an original intrusive formation “for which no analogues have yet been found in Altai” (Kuznetsov, op. cit., p. 56). These granites form a series of small bodies within the Kurota graben; Yu. A. Kuznetsov considers them genetically connected with the acid effusives of the Kurota–Ursul Formation.

It is not my task to give even the most cursory review of the Devonian intrusions of Altai; for me it is important only to note that the manifestation of the Telbes diastrophic cycle in Altai was expressed not only in the dislocation of the corresponding formations, but was also accompanied by the emplacement of intrusions. Examples of the Telbes intrusions of Altai are the above-mentioned diabases and riebeckite granites of the Kurota graben, and also, apparently, the Shebalino adamellite pluton, situated nearby, within the Seminsky Range, near the village of Shebalino (Radugin).

ж) Stratigraphy of the Kurota Devonian

Bringing together all the materials set forth above on the Devonian of the Kurota graben, we obtain the following composite section from top to bottom:

Main intrusion of the Kurota graben, which produced diabase sills among the deposits of the Kurota Formation.

Kurota Formation \(D_2^3\): clay shales with interbeds of sandstones, limestones, and intraformational conglomerates; typical index fauna: spirifers of the group Sp. cheehiel, Sp. mucronatus, Productella spinulicosta.

Break

Antropovskaya (?) Formation \(D_2^2\): bedded porphyrites, interbedding of gray sandstones and red shales, conglomerate at the base.

Intrusion of alkaline granites in the southern (and northern?) part of the Kurota graben.

Kurota-Ursul Formation \(D_2^1—D_2^2\): acidic effusives, to which clastic rocks, playing an insignificant role in the composition of the formation, are subordinate; thickness—up to 4 km.

Break.

Formation with the Tytkeskensk horizon \(D_2^1?\): a marine formation containing limestones with a coral fauna, presumably of Lower Eifelian age.

Long break.

Ongudai Formation \(D_1^1?\): a substantially pyroclastic sequence, consisting of effusives of medium basicity and subordinate lilac-green sandstones and shales.

Break.

Karakudjur Formation \(S_2—D_1?\): a variegated sedimentary sequence, consisting of interbedded shales and sandstones with a conglomerate at the base.

As already noted above, the position of the Tytkeskensk horizon in this scheme is not precisely determined. Likewise, the position of the alkaline granites also requires further clarification; we placed them below the Antropovskaya and Kurota formations only on the grounds that Yu. A. Kuznetsov (1939, p. 56) describes their contact effect on the effusives of the Kurota-Ursul formation, and at the same time this author, who made a special petrographic study of the magmatic rocks of the Kurota graben, considers the alkaline granites to be genetically connected with the effusives of the Kurota-Ursul formation. It is possible, however, that they are also younger, if one takes into account that in Gornaya Shoriya an intrusion of alkaline syenites is known, corresponding to the Abadam phase of tectogenesis.

Fig. 16. Schematic correlation of the sections of Devonian deposits of the Kurota (k) and Belgebash (b) grabens.

The correlation of the Devonian of the Kurota and Belgebash grabens is shown schematically in Fig. 16. The Upper Devonian in the Kurota graben has not been established.

3. Devonian of the Terektinsky Range

Within the Terektinsky Range, Devonian deposits were discovered by A. S. Egorov (1936) recently. They represent a narrow,

an intermittent belt of deposits, elongated almost latitudinally, resting as a basal conglomerate on Cambrian porphyrites and truncated along the northern boundary by a tectonic contact with the Silurian formations. The Devonian deposits here are represented only by sedimentary rocks, in part red-colored, and contain, in several horizons, fauna which, unfortunately, has remained unstudied up to now. A section of these deposits was described by A. S. Egorov for the watershed ridge (Fig. 13) between the headwaters of the Kara-Airy rivers (a tributary of the B. Katanda River) and the Chernaya (a tributary of the Chendek River); the Devonian formation, which may be called the Kara-Airy formation, has a thickness of more than 500 m and consists (from top to bottom) of the following rocks (after A. S. Egorov):

Rock	Thickness
Yellow marly limestones with a fauna of brachiopods and crinoids (horizon c)	35 m
Yellowish-gray calcareous sandstone	15 m
Red calcareous sandstones	200 m
Yellowish-gray calcareous sandy-argillaceous shales with thin interbeds of limestone	60 m
Gray, platy limestones, marly in the upper part; fauna of brachiopods and corals (horizon b)	65 m
Gray calcareous sandstone with plant impressions	19 m
Dark-gray and black limestones with a fauna of brachiopods (horizon a)	107 m
Yellowish-reddish fine-pebble conglomerates—visible thickness	35 m
Total thickness	> 530 m

The attitude of the rocks: strike—latitudinal, dip to the N, 70–80°; along the strike the Devonian rocks (with interruptions) have been traced westward to the headwaters of the Kaznakty River, where conglomerates and red-colored sandstones predominate (apparently only the lower members of the formation occur here).

In the article by A. S. Egorov (ref. 1, p. 74) very scanty data are given on the fauna: from horizon a—Spirifer mucronatus Cong. and Stropheodonta aff. concava Hall; from horizon b—Stropheodonta aff. diitertii Murch. and Dalmanella aff. tioga Hall—(determinations by L. N. Kraevskaya); on the basis of these determinations, horizon “a” was assigned to the Givetian stage, horizon “b” to the Frasnian.

In its character and in the presence of Lower Frasnian deposits, the Kara-Airy formation is similar to the Devonian of the southeastern part of Altai.

VIII. Devonian of the southeastern part of the Gorny Altai

First of all, let us note within what limits we here understand the southeastern part of Altai: the boundary between it and the central part of the Gorny Altai is drawn by us, approximately, along a line crossing the Chuya River east of the village of Chibit and the Argut River below the mouth of the Ingur River; on the map (Fig. 13) it is shown by a dotted line. This boundary is entirely conventional, but for a review of the Devonian deposits it is convenient, since to the northwest and to the southeast of it the composition and character of the Devonian deposits differ substantially.

The Devonian deposits of the southeastern part of Altai, as accepted within the indicated limits, are represented by two different types of formations corresponding to different stratigraphic intervals: a) black shales and limestones, intensely dislocated and regionally phyllitized, with very poorly preserved Middle Devonian fauna—the Kara-Kem and Chagan-Uzun formations; b) red-colored effusive-sedimentary sequences, weakly dislocated and unmetamorphosed, containing in limestone and marly interbeds an abundant fauna of Upper—

of the Givetian and Frasnian stages—the Bugusun, Ak-Kaya, Yustyd, and other formations.

Deposits of the second type have two areas of development within Southeastern Altai: 1) in the upper reaches of the Chuya River—in the basins of the Bugusun and Yustyd rivers they form broad fields, within which the Devonian formations occur relatively undisturbed; the Ak-Kaya Formation, developed farther west (Fig. 13), along the western margin of the Chuya Steppe, has a similar mode of occurrence; 2) along the middle course of the Chuya River, in the basin of its right tributaries, on the southern slope of the Kurai Range—here the Devonian formations have been preserved only as fragments squeezed in tectonic wedges among older deposits; the tectonic conditions in these wedges are often extremely complex.

The review of the Devonian deposits of Southeastern Altai given below is based chiefly on materials available in the literature. I considered it necessary to bring these materials together in order to achieve the greatest possible completeness in the correlation of the Devonian deposits of Altai that I have undertaken, and also because these materials, scattered through a number of different works, are usually very schematic in character and only when linked with the data set out above on the Devonian of other parts of Altai do they acquire a more definite character. Finally, some of the published materials require critical revision, again in connection with their comparison with the available data on the Devonian of other districts of the Sayano-Altai region and other parts of Altai. In carrying out this work I was unable to make use of unpublished materials, which, of course, to a certain extent affected the completeness of my summary; likewise, some paleontological collections gathered from the Devonian deposits of Southeastern Altai proved inaccessible to me, and I had to be satisfied with the scanty paleontological data available for them in published materials (mainly from determinations by L. N. Kraevskaya).

1. Deposits of the Karagem Inland Sea

In Southeastern Altai, in the basin of the Chagan-Uzun and Kara-Gem rivers, there are very distinctive Middle Devonian deposits, the like of which we do not know in other parts of Altai; they are grouped under the names Chagan-Uzun and Karagem formations.

The Chagan-Uzun Formation is developed within a tectonic depression having an almost latitudinal strike and coinciding with the basin of the Chagan-Uzun River (a left tributary of the Chuya River). A detailed description of this formation has not been published, but in brief characterizations it is outlined rather clearly by various authors; I quote: “Its complex of black limestones, black argillaceous and sandy-argillaceous shales, black siliceous shales, black conglomerates, etc., is distinctive” (Speransky, 1937, p. 134). “The rocks of this formation are strongly dislocated and schistose. In the limestone horizons there occurs, in poor preservation, a fauna of brachiopods and corals of Middle Devonian age” (V. Kuznetsov, 1937, p. 113). “In our area the formation is represented by typical black and gray argillaceous shales, finely interbedded with similar calcareous and marly sandstones... Occasionally deformed organic remains of poor preservation are encountered. In one case it was possible to identify Spirifer cf. cuspidata var. humilis Scup., ranging from \(S_1\) to \(D_2^1\). K. V. Radugin identified from here Pachypora cervicornis” (V. Kuznetsov, 1939, p. 314). Prof. M. K. Korovin (1933, pp. 346–347) noted that the Chagan-Uzun Formation is of special interest in comparison with deposits of the ty-

of the modern Black Sea deposits; we shall return to this indication by M. K. Korovin below.

The Karagem Formation was established by the investigations of F. N. Shakhov (1933, pp. 18–19); it is developed in the basin of the Karagem River (a tributary of the Argut River) and is composed of intensely dislocated rocks that have undergone regional metamorphism. The formation has the following composition: in the lower part gray marbled limestones predominate, which, with considerable recrystallization, become white; in the upper part the formation is composed of massive greenish calcareous sandstones and black phyllitized shales displaying intense cleavage. The limestones, sandstones, and shales are connected with one another by gradual transitions. The rocks of the Karagem Formation often show strong impregnation by pyrites. In the limestones, “very poorly preserved remains of organic formations” were found (ibid., p. 18).

The organic remains found in the limestones of the Karagem Formation have not been studied. Therefore the question of the age of this formation remains open, and different authors are inclined to assign to it very different ages. F. N. Shakhov notes the great similarity of this formation (in lithological respects) to the Silurian strata of neighboring districts; other authors consider the Karagem suite to be a direct westward continuation of the Chagan-Uzun Formation, to which a Middle Devonian age is assigned. In this connection the following remarks must be made: a direct transition along strike from the Karagem Formation into the Chagan-Uzun has not been traced, since between the areas of their development there “remained a geologically unilluminated belt” (Shakhov, 1933, p. 3). On the other hand, one cannot fail to note certain differences in the lithological composition of the formations being compared: alongside black shales, gray limestones and greenish-gray sandstones play a large role in the Karagem Formation; thus, the black color of the rocks, so characteristic of the Chagan-Uzun Formation, is not so fully maintained in the rocks of the Karagem suite. It may be, however, that these differences are merely of facies character, which is especially probable given the close proximity and the coincident strike of both formations. Lacking data for a more complete comparison of their lithological composition, I retain both formation names, although it may be that in the future they will prove to be united under one of them.

The age of these formations cannot be regarded as precisely established; in this respect we can be guided only by the indications of the authors cited above concerning the presence in the Chagan-Uzun Formation of a poorly studied Middle Devonian fauna, probably of pre–Upper Givetian age. An approach to refining the age of the Chagan-Uzun Formation may be made by comparing it with other Devonian formations of Altai. Let us note, first, that the Upper Givetian deposits developed nearby are less strongly dislocated, are not phyllitized, and contain characteristic representatives of the Chialian fauna.

Lower Devonian marine deposits are known only far to the northwest, in the Kuyagan-Anui zone. The most probable stratigraphic interval within which the Chagan-Uzun Formation could fit is the interval of the Eifelian–Lower Givetian stages. Eifelian marine deposits are known in the northwestern and central (Kurota graben) parts of Altai; in the Kurota graben they appear to be less metamorphosed and have a different composition (Tytkesken coral limestone).

The facies differences of the Chagan-Uzun Formation (if an Eifelian age is assigned to it) from the Eifelian deposits of Northwestern and Centـ

of Central Altai can be explained by means of paleogeographic analysis, which, however, because of the poor study of the Altai Eifelian, is of a purely preliminary character. It was indicated above that in Lower Eifelian time, within Central Altai, a deep marine bay extended from the northwest, from the limits of the Anui–Kuyagan trough; it was connected with the open sea, represented a normal marine basin, and was inhabited by a normal-marine fauna (tentaculitids). Farther to the southeast, in the basin of the Chagan-Uzun—Karagem rivers, there was an inland marine basin (we shall call it the Karagem inland sea), which had a very limited connection with the Eifelian bay of Central Altai. In its character the Karagem sea, in the opinion of M. K. Korovin, was similar to the present-day Black Sea, as is indicated by the character of the black rocks composing the Chagan-Uzun Formation. At present, with the Chagan-Uzun Formation poorly studied, it is impossible to outline in any detail the regime and history of the Karagem sea; one can only suppose that in its shallow-water areas there originally lived a normal marine fauna (brachiopods and tentaculitids). The diagonal bedding and wave-surf marks observed in places in the rocks of the Chagan-Uzun Formation (Kuznetsov, 1939, p. 314) indicate the presence in it also of coastal deposits.

It is possible that later, after the Lower Eifelian sea withdrew from the limits of Central Altai (and the Anui–Kuyagan zone?), the Karagem basin still existed for some time as a completely isolated sea-lake, in which the rocks composing the Chagan-Uzun and Karagem suites continued to be formed. But by the beginning of the Upper Givetian transgression, which also encompassed Southeastern Altai, the Karagem basin had not only been drained, but its plastic deposits had also been dislocated during one of the phases of the Telbes diastrophic cycle. The rather intense metamorphism (phyllitization) of the deposits of the Chagan-Uzun and Karagem formations is due to local conditions, since “it has the character of dislocation metamorphism, clearly connected with a zone of disjunctive disturbance…” (V. Kuznetsov, 1939, p. 315).

2. Deposits of the Upper Givetian transgression

These deposits are widely developed along the margins of the eastern part of the Chuya steppe, partly along its western margin and, in the form of remnants, along the southern slope of the Kurai Range, along the middle course of the Chuya River. They are denudation remnants of a Devonian cover, lying on various Lower Paleozoic and Precambrian strata that had been eroded before the deposition of the Devonian formations. These Devonian deposits are characterized by the presence of a thick basal conglomerate at the base, an abundance of effusives and tuffs in the lower part, and variegated sedimentary formations in the upper part; interbeds of limestones usually have a subordinate significance, but in the limestones at a number of points an abundant marine fauna of the upper Givetian stage and lower Frasnian has been found. These Givetian deposits are known in the literature under the name of the Chibit Formation (Krasnopeeva, 1935). Local expressions of the Chibit Formation are the Bugusun suite (Nekhoroshev, 1932, pp. 85–86; Krasnopeeva, 1935, pp. 67–68) of the headwaters of the Chuya River and the Ak-Kaya suite (Krasnopeeva, op. cit., p. 68; V. Kuznetsov, 1937, pp. 113–114) of the basin of the Chagan-Uzun River. The composition of the Chibit Formation is subject to local variations and, apparently, at different points different horizons of it have been characterized faunistically. Thus, I had occasion to examine a small collection

brachiopods (Khalfin, 1935, p. 10), derived from the basin of the Chagan-Uzun River and consisting of a typical complex of forms of the supraphalaena fauna: Anathyris supraphalaena, Anathyris peetzi, Douvillina dutertrii, Productella subaculeata—a typical association of the very lowest beds of the Frasnian stage. P. S. Krasnopeeva (1935, p. 68) also indicates from the Chibit Formation Spirifer verneuili, and V. A. Kuznetsov (1937, p. 114)—Spirifer archiaci; if only these identifications are correct, then within the Ak-Kaya Formation there are horizons of the Frasnian stage that are higher than anywhere else in Gorny Altai. This circumstance would be of great importance for certain paleogeographic conclusions; however, I have definite grounds for refraining from these conclusions until I have personally examined the fauna of the Ak-Kaya Formation.

More ancient deposits occur within this formation in the basin of the upper reaches of the Chuya River (the Bugusun Formation); here the Chibit Formation contains an Upper Givetian horizon with a very abundant and very typical chialevo fauna. I have at my disposal fauna from a certain horizon of the Bugusun Formation, which is exposed in the Kizylshin gorge (in the lower course of the Bugusun River); this Kizylshin horizon of the Chibit Formation is characterized by the following fauna:

Productella subaculeata (Murch.)
Productella spinulicosta Hall
Productella productoides (Murch.)
Leptaena rhomboidalis (Wilck.)
Schellwienella umbraculum (Schl.)
Stropheodonta pseudasella n. nom.
Stropheodonta cf. interstrialis (Phill.)
Aulacella eifeliensis (Vern.)
Schizophoria striatula (Schl.)
Uncinulus korovini Khalf.
Camaratoechia sp.
Spirifer cultrijugatiformis Khalf.
Spirifer cheehiel Kon.
Spirifer cheehiel Kon. var. semicostalis Khalf.
Spirifer cheehiel Kon. var. mesoloba Korovin
Spirifer martianoffi Stuck.
Cyrtina heteroclita (Defr.)
Cyrtina heteroclita (Defr.) var. intermedia Oehl.
Athyris concentrica (Buch)
Atrypa reticularis (Linn.)
Atrypa desquamata Sow.

The most extensive quantitative development in the Kizylshin fauna is shown by Spirifer cheehiel and Spirifer martianoffi; in stratigraphic position and facies type the Kizylshin horizon is equivalent to the Korgon-Yelovka Formation (p. 91); the composition of the fauna and the petrographic composition (including the presence of effusive components) oblige us to assign the deposits of the Kizylshin horizon to the Korgon facies of the Upper Givetian stage of Altai (p. 93).

But within the Bugusun Formation there are also higher, namely Lower Frasnian, horizons, which I cannot characterize in the same detail as was done above for the Kizylshin horizon, since I did not have at my disposal fauna from this upper part of the Bugusun Formation. P. S. Krasnopeeva (1935, p. 68) indicates from this upper part Spirifer ex. gr. Sp. tenticulum Vern. and Rhynchonella ex gr. Rh. cuboides Sow. In the work of D. V. Nalivkin

(1938), who described the Bugusun fauna, cites such typical Lower Frasnian forms as Anathyris supraphalaena, Hypothyris venustula, Productella arctirostrata, Spirifer aff. tenticulum, and others. It may be regarded as established that within the Bugusun Formation there are not only Upper Givetian deposits, but also Lower Frasnian deposits with a supraphalaenid fauna. Thus, in stratigraphic composition the Bugusun Formation is identical with the Malafeevka Formation, but has a different facies character. Incidentally, it should be noted that between the Upper Givetian and Lower Frasnian parts of the Bugusun Formation there is apparently a certain erosional break (Krasnopeeva, p. 68). D. V. Nalivkin (p. 1), on the basis of the above-mentioned Lower Frasnian forms, assigns the entire Bugusun Formation, including the Kyzylshin horizon with its typical chielevoi fauna, to the Upper Devonian; the composition, distribution, and relationships of the chielevoi and supraphalaenid faunas have been clarified and characterized to such an extent that it seems unnecessary to us to offer any additional considerations to prove the erroneousness of this conclusion by D. V. Nalivkin.

In addition to the Chibit Formation, with such local manifestations of it as the Bugusun Formation and the Ak-Kaya Formation, Devonian deposits of a different character occur in southeastern Altai; they are known in the literature under the name of the Ustyd Formation (Krasnopeeva, 1935). This formation differs sharply from the Chibit Formation; it consists of greenish-gray and black sandstones and clayey shales with rare interbeds of limestones; at the base of the formation there is a conglomerate with quartz pebbles. In the section along the Ustyd River (headwaters of the Chuya River), P. S. Krasnopeeva (1935, p. 69) notes the presence, in the lower part of the Ustyd Formation, of the Givetian Sp. mucronatus and Sp. martianoffi among brachiopods, and Fenestella tscheremschanka among bryozoans; in the upper part of the formation, where red-colored sandstones also appear, the Upper Devonian Spirifer bouchardi and Spirifer verneuili are present.

Apparently, the faunistically characterized deposits in the headwaters of the Chuya and Bashkaus rivers, discovered by N. N. Smirnova, belong to the Ustyd Formation:

Lithologically, at the base of the sequence the rocks of \(D_2\) are represented by thin-bedded, easily splitting into separate slabs, bluish marly shales containing a brachiopod fauna, with interbeds of coarse quartz-feldspathic sandstones. The upper horizons of this sequence are enriched with interbeds of friable sandstones.

In addition, horizons of light-green sandstones and lilac clayey shales appear. Already at the very northern margin of the Kokorya and Chuya steppes there appear thin interbeds of light-gray limestones, abundantly containing a fauna of bryozoans and corals.... The entire \(D_2\) sequence is gathered into more or less gentle folds of latitudinal or northwestern strike. Dip angles vary from 45° to 80°.... Along its northern boundary, black shales and sandstones (\(D_2\)) are in contact with a green metamorphic sequence \(S_1\) (?). Disjunctive disturbances have been traced in several places. They have a strictly persistent latitudinal strike and are sharply expressed even in the relief; moreover, it can be established that the bed of black \(D_2\) shales dips beneath the green sequence at an angle of 70° to the north. Along the southern boundary this sequence is immediately overlain by Quaternary deposits” (Khalfin, 1935, pp. 8–9).

The brachiopod fauna collected by N. N. Smirnova in this sequence is very small and monotonous, being represented exclusively by spirifers. The dominant form is Spirifer martianoffi Stuck., showing no differences from the Korgon representatives of this species. Besides it, there is only Spirifer mucronatus Conr. No Upper Devonian elements have been found in this fauna. On the other hand, the presence of only the just-mentioned Upper Givetian forms excludes the possibility of stratigraphic identification (see V. Kuznetsov, 1939, p. 314) of the sequence characterized here with the Chagan-Uzun Formation, unless this latter also is assigned to the Upper—

Givetian age, which at present appears unlikely. The relations between the Yustyd and Chibit formations remain unclear; the fauna of the Yustyd Formation must be reworked anew and in greater detail on the basis of more extensive collections.

3. The Aktash Formation

Not only Carboniferous, but also Famennian and even Upper Frasnian marine deposits are unknown in the Gorny Altai. It is therefore understandable what interest was aroused by A. S. Mukhin’s report (1936) on his discovery of marine Carboniferous deposits in southeastern Altai. These deposits are developed along the southern slope of the Kurai Range; they are “represented by small tectonic bodies, sharply truncated along a large latitudinal or northwestern thrust zone... the total length of such an intermittent belt of Permo-Carboniferous reaches 50 km” (Mukhin, 1936, p. 67). These deposits have been studied in greatest detail 18 km east of the village of Chibit (Fig. 13); here, in the system of the Yarnu-Airy River, along its tributary Aktash, A. S. Mukhin observed, among argillaceous shales with Noeggerathiopsis aequalis and Aneimites lopatini (determinations by Prof. V. A. Khakhlov), a bed of limestone, often pinkish in color, with an abundant brachiopod fauna of very good preservation. At the same time, special observations “confirmed the normal interbedding of the bed of faunistically characterized limestone with productive shale-sandstone formations” (Mukhin, op. cit., p. 70).

If, in this case, Permo-Carboniferous continental deposits with cordaites are indeed interbedded with marine brachiopod limestones, this is of exceptional interest, far exceeding the scope of local Altai geology. It would seem that this brachiopod fauna should have been subjected to careful and complete study; unfortunately, this work, carried out by L. N. Kraevskaya, was performed quite unsatisfactorily. For so responsible a case, L. N. Kraevskaya’s determinations yielded the following list of fauna:

Rhynchospira sp.
Retzia sp.
Ptychospira (?) sp.
Acanthospira aciculifera (Rowley)?
Brachythyris aff. peculiaris (Schum.)?

In this list, out of five names, three are only generic and three are accompanied by question marks; in addition to this meager list, it is further stated that in this fauna “some forms resemble the Upper Devonian Spirifer conoideus and Spirifer tenticulum, but study of their internal structure showed that they possess either a septum or a pseudosyrinx, which compels one to refrain from assigning them to the genus Spirifer” (Mukhin, op. cit., p. 69). It is not surprising that from these “determinations” follows the corresponding conclusion: neither Devonian nor Carboniferous (“more likely Lower Carboniferous than Upper Devonian”—Mukhin, op. cit., p. 69).

To the above it remains to add that A. A. Saukov (1937, p. 172), according to determinations by E. Soshkina, cites from the same locality and, evidently, from the same limestone:

Spirifer aff. archiaci Murch.
Spirifer aff. disjunctus Sow.
Retzia tschernyschewi Peetz var. β Khalif.

The spirifers from this list are typical Upper Devonian forms; Retzia tschernyschewi var. β was established by me in the Lower Frasnian deposits of the Kuzbass (Khalfin, 1932, p. 22).

Were it not for A. S. Mukhin’s categorical statement that the limestones with this fauna occur conformably within the shales with cormophytes, I would, without hesitation, have assigned these limestones (on the basis of E. Soshkina’s determinations) to the Chibit Formation. At present, however, we can only note a phenomenon that has not yet been explained—the occurrence of limestone with Upper Devonian brachiopods within continental rocks with Noeggerathiopsis aequalis and Noeggerathiopsis tchirkovae. A full and detailed study of the fauna collected by A. S. Mukhin will greatly assist in resolving this question¹.

Chapter III

Correlation and Paleogeography

(Summary)

In this chapter we shall attempt to summarize the material set forth above on the Devonian deposits of the Altai.

In Chapters I and II there are a number of particular stratigraphic schemes relating to the Devonian deposits of different parts of the Altai; here we give a stratigraphic correlation of these deposits (Table 23), explaining it with brief comments. On the other hand, we shall summarize those observations made in the preceding chapters with regard to the Devonian history and geography of the Altai. These generalizations cannot be exhaustive—primarily because in the preceding account we considered the Devonian deposits only of the Anui–Chuya depression. The Devonian of the Rudny Altai remains unexamined, as do the Devonian deposits of that graben which forms the southern continuation of the Kuznetsk basin and passes west of Lake Teletskoye (on the maps in Figs. 19 and 20 it is shown by oblique hatching). Our study of the Devonian deposits and Devonian fauna of the Anui–Chuya depression has yielded much material for clarifying and refining the stratigraphy of the Devonian of the Rudny Altai, in particular its Lower Devonian deposits, characterized by leptodontellid fauna. The continuation of the present work is devoted to the Devonian of the Rudny Altai. Therefore we shall return in the future to questions of correlation and paleogeography of the Devonian of the Altai, when we shall be able to do so with greater completeness; in particular, we do not consider it expedient to include here paleogeographic maps, which would require more extensive explanations in the part concerning the Rudny Altai.

Only for the convenience of the reader do we provide two such maps (Figs. 19 and 20): they make it possible to see the position of those geographic elements of the Altai that are mentioned in the text. Let us note that these are only schemes, depicting the general plan of the geography of the Altai in the corresponding age, but not the exact position of the boundaries of basins. As for those Devonian formations of the Rudny Altai that are mentioned in Table 23, for their brief explanation we give several excerpts from the “Dictionary of Stratigraphic Terms of the Devonian System of the Sayan–Altai Region,” compiled by us.

Our review of the Devonian deposits of the Altai would be incomplete if we did not attempt to correlate them with the Devonian deposits of other regions of the Sayan–Altai area; this correlation is given in Table 27. The study of the Devonian deposits of the Altai (as can, in part, be seen from Table 27) substantially supplements our ideas about the composition of the Devonian system of Siberia. On the basis of all the materials considered above, in conclusion we propose a new composite stratigraphic scheme of the Devonian of the Sayan–Altai region (Table 28), in which we give paral-

…zation of marine and continental formations and horizons, and notes all phases of the Telbes tectogenesis cycle known at the present time.

1. Correlation of the Devonian Deposits of Altai

In the preceding chapters the factual material relating to the Altai Devonian is set forth, and a stratigraphic and facies analysis is given of the various Devonian formations of Altai. Table 23¹ presents a stratigraphic summary of the Devonian system of Altai. This summary is detailed and reliable to varying degrees in its different parts; it is not always possible to parallelize the formations of the different regions of Altai with complete confidence.

The greatest detail and reliability characterize those parts of our stratigraphic summary of the Devonian of Altai whose development is based on a sufficiently complete and detailed study of the fauna. This applies, first of all, to the Lower Devonian of the Anui–Kuyağan zone, and then to the deposits of the upper parts of \(D_2\) and the lower parts of \(D_3\). In Rudny Altai the reference stratigraphic localities are the Losikha limestone for \(D_1\), and the Goniatite and Nikolaevka horizons for \(D_3^1\). But, of course, in our stratigraphy of the Devonian of Altai there are still many doubtful and schematic elements. This applies first of all to the Eifelian deposits: as has already been noted above, it is precisely the Eifelian fauna of Altai that has been studied most poorly; therefore both the stratigraphic position of the Eifelian formations in our scheme and their correlations are preliminary in character. The stratigraphy of the Lower and Middle Devonian of Rudny Altai is poorly developed; the position of the Batun, Akimovka, Murzinka, and Kuryinsky formations requires clarification on the basis of a more detailed study of their fauna; further investigations in this field will, it must be supposed, introduce substantial additions and corrections into our scheme.

Likewise, further confirmation (or correction) is desirable for the stratigraphic position and correlation adopted by us for the effusive formations of the Lower (Kuyağan–Ongudai) and Middle (Korgon–Belgebash-Chuya–Kurota–Ursul) Devonian. Finally, with respect to those stratigraphic intervals for which the absence of deposits is indicated in our scheme, the following must be noted: in a number of cases these intervals will subsequently be filled, of which I have no doubt; the absence of certain formations in these segments of our scheme is due to three causes: 1) in a number of cases the corresponding deposits are indeed absent in one or another part of Altai; 2) in other cases they simply have not yet been discovered; 3) finally, at times they have been established, but remained unknown to me (I have already noted that some unpublished materials were not used by me), or the information about them is too uncertain (for example, the red-colored deposits in the upper reaches of the Kodrin River, a tributary of the Katun, which, according to K. V. Radugin, may be Upper Devonian).

The present state of knowledge of the Devonian fauna of Altai is such that in a number of cases it does not provide the general stratigraphic scheme with the necessary paleontological evidence in all its parts. At the same time, however, the material accumulated on this question is so considerable that, without coordination and critical analysis of it, further work would have to encounter substantial difficulties. If the stratigraphic scheme proposed by me, being only one of the sta—

¹ Tables 23, 27, and 28, without commentary, were published in 1942 in the collection of theses of the scientific-technical conference dedicated to the 25th anniversary of the Great October Socialist Revolution (Tomsk Polytechnic Institute).

Table 23

Correlation of Devonian Deposits of the Altai

Units of the international stratigraphic scale	Southwestern Altai (Rudnyi Altai, basin of the Uba and Ulba rivers)	Western Altai (Korgon Range and northern part of Rudnyi Altai; basins of the upper reaches of the Charysh and Alei rivers)	Northwestern Altai (Anui–Kuyagan zone; basins of the Peschanaya and Anui rivers)	Central Altai (basin of the middle course of the Katun River)	Southeastern Altai (basin of the middle and upper course of the Chuya River)
DC Etrenskian stage	Tarkhan Formation: clayey shales with a fauna of mixed Devonian–Carboniferous type (Spirifer disjunctus Sow., Spirifer tornacensis Kon. et al.).	Absent	Absent	Absent	Absent
D32 Famennian stage	Tarkhan–Ulba Formation: basic tuffs, sandstones, and clayey shales with Productus ex. gr. Pr. praelongus Sow., Spirifer aff. archiaci Vern. et al.	Absent	Absent	Absent	Absent
D31 Frasnian stage	Break? Nikolayev tectogenesis phase.	Absent?
D31 Frasnian stage	Effusive tuffaceous complex (supra-Nikolayev, Borovlyanskaya, Chudakskaya formations). Nikolayev horizon: limestones with Hypothyridina cuboides, Spirifer zickzack et al. Effusives and tuffs. Tonatytov horizon: red limestones with Manticoceras intumescens, Beloceras et al.	Bukholov horizon: black shales and sandstones with Buchiola retrostriata et al. Break—Barzaska tectogenesis phase. Korgon–Yelovka Formation: dark-gray sandstones and marly shales; interbedding of acid effusives with sandstones and shales; at the base a conglomerate; typical Chizha fauna.	Malafeyevka Formation: gray and greenish-gray clayey shales with subordinate beds of sandstones; at the base, conglomerate. Strata with Spirifer disjunctus s. str. Strata with Anathyris supraplana. Strata with Spirifer mucronatus. Strata with Spirifer cheehieli.	Absent	Chibit Formation: variegated sequence composed of interbedding of acid and basic effusives with various sedimentary rocks; at the base a conglomerate. In the upper part, a superhorizon fauna; in the lower (Kyzyl-Shin) horizon, typical Chizha fauna. Rostov Formation: dark-gray shales and sandstones—a locally pronounced analogue of the Chibit Formation (?)
D23 Upper Givetian stage	Undifferentiated effusive-sedimentary sequence. (Talovka Formation of the Shemonaykha–Lokot district.)	? Kurya limestones. Murzinka Formation: limestones, sandstones, conglomerates; fauna: Leptothyrillum sp., Hypothyridina implexa, Camarophoria subteragona.	Break in sedimentation.	Kurota and Belge-Bash formations: dark-gray shales and limestones with beds of sandstones and intraformational conglomerates; typical Chizha fauna (beds with Spirifer cheehieli and beds with Spirifer mucronatus). Break—Antropovka tectogenesis phase. Antropovka (?) Formation: brecciated porphyrites, gray sandstones and red shales, basal conglomerate (continental deposits).
D22 Lower Givetian stage	Undifferentiated effusive-sedimentary sequence. (Talovka Formation of the Shemonaykha–Lokot district.)	Break—Telbes tectogenesis phase, accompanied by intrusion of alkaline granites. Korgon Formation: red and lilac quartz porphyries and albite porphyries, accompanied by their pyroclastic equivalents (subaerial formations). Akimovka Formation: sandy and marly limestones and calcareous sandstones with Ambocoelia, Metaplasia, Chonetes minuta et al.	Break in sedimentation. Augite and plagioclase porphyrites and their pyroclastic equivalents. Break—Akimovka tectogenesis phase. Eifelian limestones with Solovikhinia, Coenites fructicosum et al.	Belge-Bash–Chuya (subaerial) and Kurota–Kursai (subaquatic) formations: acid effusives alternating with sandstones, shales, and limestones. Tytkesken horizon of the Kurota graben: coral limestones.	Break in sedimentation.
D21 Eifelian stage		Break—Medvedev tectogenesis phase.			Chagan-Uzun and Karagem formations: phyllitized black shales, black sandstones, black limestones and conglomerates; more rarely gray sandstones and limestones; poor fauna of brachiopods and corals.
D13 Upper Koblenzian stage	Undifferentiated deposits of various facies with leptocoeliid fauna. Ridder Formation with Phacops altaica, Athyris undata, Spirifer sibiricus et al.	Batun Formation (partly): shales, sandstones, and limestones with Spirifer paucicostatus et al. Deposits of the Cherepanovo mine with Pleurodictyum.	Medvedev Formation: greenish-gray marly shales and sandstones, unschistose limestones; at the base a conglomerate; leptocoeliid fauna: Leptodontella planuscula, Spirifer korovini, Conchidium celsiseptosum et al. Break—Kuyagan tectogenesis phase. Kondatyevka Formation: massive thin-bedded and clayey rocks; at the base a conglomerate; leptocoeliid fauna: Leptodontella rotundata, Probolium altaicum, Pleurodictyum sp. et al.	Absent	Absent
D12 Lower Koblenzian stage	Undifferentiated deposits of various facies with leptocoeliid fauna. Ridder Formation with Phacops altaica, Athyris undata, Spirifer sibiricus et al.	Batun Formation (partly): shales, sandstones, and limestones with Spirifer paucicostatus et al. Deposits of the Cherepanovo mine with Pleurodictyum.	Break—Ganin tectogenesis phase.	Absent	Absent
D11 Zlichovian stage	Losikha limestone with leptocoeliid fauna: Leptodontella rotundata, Leptaena bouei, Schuchertella altaica, Delthyris perlammellosa et al.	Kurya–Lokot limestones with a fauna of the Bohemian type—Stropheodonta stephani, Chonetes verneuili et al. Deposits of Zmeinogorsk with leptodontellid fauna.	Ganin Formation. Paramonigeniev horizon: lagoonal deposits with Aminigenia altaica, Laurskia attenuata et al. Leptodoratov horizon: marine marly limestones and shales with Leptodontella rotundata, Delthyris perlammellosa, Eospirifer pseudohastatus et al. Rensseleriid horizon: limestones with Rensseleria, Spirifer geyeri et al. Kuyagan Formation: strata of mixed effusive-sedimentary and sedimentary rocks in the lower, middle, and upper horizons; green and lilac porphyrites.	Ongudai Formation: pyroclastic continental sequence composed of effusives of intermediate composition and subordinate lilac and green sandstones and shales.	Absent
SD Zhedinian stage		Break—Solovikha tectogenesis phase. Talovka and Borovushka limestones with coral fauna of mixed Silurian–Devonian type.	Solovikha limestone with fauna of the Bohemian type: Atrypa umbra, Atrypa comata, Atrypa insolita et al.
Cm + S		Erian folding	Erian folding	Erian folding	Erian folding
Cm + S		Silurian and Cambrian formations	Silurian and Cambrian formations	Silurian and Cambrian formations	Silurian and Cambrian formations

...in the study of the Devonian of Altai, proves useful in the further development of a more detailed and more refined stratigraphy of this region,—I shall consider the task before me accomplished.

For clarification of the Devonian formations of Rudny Altai mentioned in Table 23 and below in the text, some excerpts are given from the above-mentioned stratigraphic dictionary of the Devonian of the Sayan-Altai region.

Akimovka Formation—Endourova, 1938—$D_2^1$, Rudny Altai.
Syn.: Murzinka Formation—Aleksandrov, 1939.

Under the name A. f., T. I. Endourova distinguished deposits developed north of the village of Akimovka along the right bank of the Talovka River; they are represented by sandy and clayey limestones and marly sandstones, lying undisturbed, with the formation of gentle brachyfolds. The fauna of the A. f. has no close analogues among other Altai faunas; it is characterized by the presence of new species of the genera Metaplasia and Ambocoelia and by an abundance of chonetids, among which T. I. Endourova cites Chonetes minuta Goldf. and Chonetes coronata Cong.

Age—presumably Eifelian; the A. f. is overlain by the Murzinka Formation.

Village of Akimovka (east of the village of Kuryinskoe, northern part of Rudny Altai).

Tschetch G. G. Trans. Geol. Part of the Cabinet, vol. VI, issue 1, pp. 62–65, 1907. Description of the deposits of the A. f.; faunal lists (determinations obsolete), the age of which is accepted as Koblenzian.

Aleksandrov A. I. Trans. I Siberian Conference on the Study of Productive Forces, vol. II, 1940, p. 323. Brief characterization of the A. f., which the author calls the Murzinka Formation.

Baklakov Formation—Baklakov, 1937—$D_1$, Rudny Altai.

Composition from bottom to top: clayey shales, sandstones, marly limestones; in the latter the fauna is: Spirifer paucicostatus Khalf., Chonetes sarcinulata Schl., Atrypa reticularis Linn. and several others, as well as Calymene sp., Pachypora sp., Pleurotomaria sp. Age—Lower Devonian, presumably Koblenzian.

The B. f. lies transgressively on Silurian deposits and is unconformably overlain by the Murzinka Formation (see).

Rudny Altai, basin of the left tributaries of the Charysh River (Loktevka—Kokuyka—Talovka rivers).

Baklakov M. S. Probl. Sov. Geol., 1937, No. 4, p. 350. Establishment of the formation, its brief characterization, age, relation to adjacent formations.

Borovikovskaya Suite—Dannikovich, 1938—$D_3$, Rudny Altai.

Tuffs and lavas of quartz keratophyres, to which various other effusives and variegated tuffaceous sandstones are subordinate. Thickness—900 m.

See Devonian effusive-sedimentary complex of Rudny Altai.

Borovushka Limestone—new name—SD, Rudny Altai.

Coral limestones with interbeds of sandstones, lying, apparently, with a concealed unconformity on a suite of marly shales, presumably of Silurian age. They contain a coral fauna in which abundant Devonian-character components predominate, while some other components (Spongophyllum cf. sedgwicki, Heliolites decinies McCoy n. var.) are Upper Silurian.

Age presumably Gedinnian; probably, the B. l. is a stratigraphic analogue of the Talovka (see) and Solov’yakha (see) limestones.

Vicinity of the settlement of Borovushka, northern part of Rudny Altai.

Baklakov M. S. Probl. Sov. Geol., 1937, No. 4, p. 349.

Bukhiolovy Horizon—new name—$D_3^1$, Rudny Altai.

Dark-gray, almost black marly-clayey shales with a fauna of pelecypods and gastropods, occurring among red limestones; buchiolas predominate: Buchiola retrostiata, Buchiola cf. conversa, Buchiola altaica n. sp., as well as Posidonia mesacosatlis, Lunulicardium sp.

The B. h. is a stratigraphic equivalent of the goniatite horizon (see).

Northwestern part of Rudny Altai (area of Lokot’ station), Gryaznukha brook, west of the settlement of Razdol’noe.

Khalfin L. L. Izv. Zap.-Sib. Branch Acad. Sci. USSR, geol. ser., 1946, issue 1.

Goniatite Horizon—Nozdreev, 1940—$D_3^1$, Rudny Altai.

The thickness and composition of the G. h. vary greatly along strike; chiefly—lavas and tuff-lavas of andesitic porphyrites, dark clayey shales, and subordinate quartz porphyrites. In the G. h., mainly in its upper part, small lenses (from several cm to 1.5 m thick) of red ocherous limestone with a rich fauna of brachiopods, corals, and mollusks are scattered; especially characteristic are the goniatites: Manticoceras intumescens, Manticoceras cordatum, Beloceras multilobatum, and others. Age—lower part of the Frasnian stage. The characterization of the G. h. is given according to the data of V. A. Nozdreev.

Rudny Altai, area of the Nikolaevsky mine.

Bublichenko N. L. Materials on the Geology of Rudny Altai, 1939, p. 72.

Zmeinogorsk sericite slates—Petts, 1907—D₁, Rudny Altai.
The Z. s. s. are characterized by a Leptodontella fauna and probably are of Zingan age. See Losikha limestone.
Petts G. G. Trudy geol. chasti kab., vol. VI, 1907, p. 199; gray sandstones with interbeds of limestones; fauna of brachiopods and pelecypods. The Z. s. s. are regarded as a stratigraphic and facies analogue of the Spiriferensandstein of the Harz and Eifel.

Kuryan limestones—Petts, 1897—D₃²–³, Rudny Altai.
Dark- and light-gray coral limestones occurring among yellowish- and greenish-gray slates and sandstones with imprints of lepidophytes. In the limestones there is a rich, chiefly coral, fauna: Cyathophyllum caespitosum, C. vermiculare, Phillipsastrea ananas, Alveolites suborbicularis, etc. The K. l. were assigned by Petts to the upper parts of the Stringocephalus stage, but, apparently, they are older than the Middle horizon (see). A revision of the identifications of the fauna is necessary.
Vicinity of the village of Kuryanskoe in the northern part of Rudny Altai.
Petts G. G. Tr. SPB obshch. est., vol. XXVIII, issue 1, pp. 236–237, 1897. Lists of fauna, determination of the age of the K. l.
Petts G. G. Tr. geol. chasti kab., vol. VI, issue 1, 1907, pp. 62–66, 207–209. Characterization of the K. l. and their enclosing rocks; list of fauna, its age.
Bublichenko N. L. Bolshoi Altai, vol. II, 1936, p. 87. Position of the K. l. in the stratigraphic column of Rudny Altai.

Losikha limestone—new name—D₁; Rudny Altai.
Light-gray marly limestones with an abundant leptodontellid fauna: Leptodontella rotundata, Leptaena bouei, Schuchertella altaica, Delthyris perlamellosa, etc.
Stratigraphic analogue of the Ganya Formation (see).
Rudny Altai, vicinity of the village of Losikha (Verkh-Ubinskoe).
Bublichenko N. L. Izv. geol., vol. XLIV, no. 10, 1927. Description of some brachiopods of the L. l.; the age of the fauna is determined as Lower Eifelian.

Murzin Formation—Aleksandrov, 1939. See Akmovka Formation.

Murzin Formation—Baklakov, 1937—D₂², Rudny Altai.
Homonym—Murzin Formation—Aleksandrov, 1939.
Composition from bottom to top: conglomerates, sandstones, and limestones. In the pebbles of the conglomerate there is a fauna of Middle Devonian amphipores and actinostromes; in the limestones—Leptoinophyllum sp., Hypothyris implexa (Sow.), Camarophoria subtetragona Schn., Atrypa aspera Schl., and some others; on the basis of this fauna the age of the M. F. is determined as Lower Givetian.
The M. F. lies transgressively on deposits of the Akmovka (see) and Batun (see) formations; the relation of the M. F. to the Kuryan limestones (see) has not been clarified.
Northern part of Rudny Altai, basin of the left tributaries of the Charysh River, east of the village of Kuryanskoe.
Baklakov M. S. Probl. Sov. geol., 1937, no. 4, p. 350. Establishment of the M. F., its relation to the Batun Formation, composition, fauna, age.
Petts G. G. Tr. geol. chasti kab., vol. VI, issue 1, 1937. Some incidental remarks on deposits in the area of development of the M. F.

Nikolaev horizon—Bublichenko, 1936—D₃¹, Rudny Altai.
Composition—predominantly clayey slates. Among them is a bed of white and pink limestone 2–4 m thick with an abundant and varied fauna; especially numerous are brachiopods, the composition of which is characterized by a mixture of Frasnian (Hypothyris cuboides, Spirifer zickzack, etc.) and Givetian (Spirifer curvatus, Spirifer undifer, etc.) forms.
The age, apparently, is within the limits of the lower half of the Frasnian stage.
Left bank of the Uba River, area of the Nikolaev deposit and southwest of it.
Danilovich V. N. Izv. Ak. Nauk, geological series, 1938, no. 2, pp. 184–185. Lists of fauna; age—transitional from D₂ to D₃.
Bublichenko N. L. Mater. po geol. Rudnogo Altaya, 1939, pp. 72–73. Lists of fauna; age—base of D₃.

Ridder Formation—new name—D₁, Rudny Altai.
Syn.: Kryukov limestones—Bublichenko, 1936.
Composition of the formation from bottom to top: acid tuffs, clayey and marly slates with interbeds of limestones, red-green basic tuffs, clayey and marly slates; thickness—about 1 km.
The R. F. occurs as an island of weakly dislocated and unmetamorphosed rocks among metamorphic deposits of the porphyroid suite (see) and the Beloubinskaya suite (see).
The fauna is diverse: Phacops altaicus Tschern., Bronteus sibiricus Tsch., Proetus oehlerti, Anarcesfes lateseptatus Beyr., Meristella ypsolon Barr., Atrypa undata Defr., etc.
The age of the R. F. is Lower Devonian, presumably Upper Coblenzian.
Rudny Altai, Ridder.

Chernyshev F. N. Izv. Geol. Kom., vol. XI, 1893, pp. 199–240. Description of the fauna (fauna of the Kryukov mine), determination of the Lower Devonian age of the R. f.

Bublichenko N. L. Bolshoi Altai, vol. II, 1936, pp. 86–91. The deposits of the R. f. are assigned to \(D^1_2\) and are correlated with the “Losikha horizon” (see).

Kurek N. N. Materials on the geology of Rudny Altai, 1939, pp. 37–38, 55–56. Characterization of the composition of the R. f.; the deposits of the R. f. are regarded as a part of the porphyroid suite (see) and the Beloubinsk suite (see) that escaped dislocation.

Talovskaya suite—Danilovich, 1938—\(D_1\), Rudny Altai.
Alternating gray and yellow shales and quartz keratophyres and tuffs; thickness—1300 m.

See the Devonian effusive-sedimentary complex of Rudny Altai.

Talovsky limestone—new name—SD, Rudny Altai.
Gray and dark-gray coral limestones, occurring as a small outlier on the right bank of the Talovka River (left tributary of the Charysh River), opposite the settlement of Murzinsky, north of Akimovka village. Characterized by a mixed Silurian-Devonian fauna: Favosites gothlandica, F. hemisphaerica, Roemeria sp., Cyathophyllum hexagonum, and others.

The age is presumably Gedinnian; probably a stratigraphic analogue of the Borovushka limestones (see) and the Solovikha limestone (see).

Aleksandrov A. I. Proceedings of the Conference on the Study of the Productive Forces of Siberia, vol. II, 1910, pp. 322–323.

Tarkhan suite—Nekhoroshev, 1939—DC, Rudny Altai.
Syn.: Tarkhan suite (in part)—Nekhoroshev, 1925 and 1937.
Composition: greenish-gray clayey shales with calcareous interbeds, thickness 600 m; the fauna of the T. s. has a mixed Devonian–Carboniferous character, with predominance of Devonian elements (Spirifer cf. verneuili and Productus cf. praelongus) in the lower part (brachiopod unit) and with predominance of Carboniferous elements (Spirifer tornacensis and others) in the upper part (retenoporinid unit).

The T. s. conformably overlies the Tarkhan-Ulba suite (see) and is conformably overlain by the Bukhtarma suite \(C_1\).

Rudny Altai, basin of the Ulba rivers (near the village of Tarkhanskoye) and Malaya Ulba.

Nekhoroshev V. P. Izv. Geol. Kom., vol. XLIV, 1925. Characterization of the T. s., establishment of an intermediate position between \(D\) and \(C\); the upper part of the Tarkhan-Ulba suite (see) is included in the T. s.

Nekhoroshev V. P. Stratigraphic Dictionary of the USSR, p. 198, 1937. Literature.
Nekhoroshev V. P. Materials on the geology of Rudny Altai, 1939, pp. 10–14. Clarification of the extent of the T. s.; a very detailed section of it, lists of fauna; the T. s. is assigned to \(C_1\).

Tarkhan-Ulba suite—new name—\(D_3\), Rudny Altai.
Syn.: Tarakhan suite (in part)—Nekhoroshev, 1925,
        ”         ”         ”         1937.

An effusive-sedimentary unit, consisting from bottom to top of basic tuffs and tuff-conglomerates, magnetite sandstones, sandstones and shales with Spirifer ex gr. Sp. disjunctus, paleandesites and their tuffs, sandstones with Spirifer cf. archiaci and Productus aff. praelongus, dark clayey shales; a large part (middle) of the T.-U. s. (with a thickness of about 700 m) is unknown. The total thickness of the T.-U. s. is not less than 1350 m.

The age of the lower part of the T.-U. s. is not precisely established; the age of the upper part is Famennian.

Rudny Altai, Ulba River, near the village of Tarkhanskoye.

Nekhoroshev V. P. Izv. Geol. Kom., vol. XLIV, 1925, p. 789.
Nekhoroshev V. P. Stratigraphic Dictionary of the USSR, p. 198. 1927.
Nekhoroshev V. P. Materials on the geology of Rudny Altai, 1939, pp. 7–10. Detailed section of the T.-U. s., preliminary lists of fauna, establishment of age.

Chudaika suite—Danilovich, 1938—\(D_3\), Rudny Altai.
Quartz keratophyres and their tuffs, greenish-gray clayey shales and tuffites, thickness—1700 m.

See the Devonian effusive-sedimentary complex of Rudny Altai.

2. Paleogeography of Altai (Devonian Period)

The compilation of materials on the Devonian deposits of Altai that we have carried out makes it possible to establish certain important features of the geological history of this region during the Devonian period. Of course, not for all parts of Altai and not for all ages of the Devonian period can we reconstruct the physico-geographical environment with the same degree of detail; here it is poss—

But it would be necessary to repeat everything that was said above on this matter in characterizing our summary stratigraphic scheme. With sufficient detail, we can outline the regime and history only of the Devonian basins of the Anui–Chuya depression. At the same time, we must, of course, remember that the Devonian geography of Altai is part of the Devonian geography of the entire Sayan–Altai region, and some questions concerning the former cannot be resolved without taking into account and analyzing broader materials relating to the Devonian system of the Sayan–Altai region as a whole. And as regards the development of a detailed paleogeography of the Sayan–Altai region, very little has yet been done. Finally, there is one more very unfavorable circumstance that hampers the resolution of certain questions of the Devonian geography of Altai: throughout the entire Devonian (and not only Devonian) history of Altai, a powerful influence was exerted by that geosynclinal marine basin (we shall call it the Siberian Sea) which lay to the north and northwest of Altai and whose deposits are almost everywhere concealed from observation beneath a thick cover of Cenozoic deposits of the part of the West Siberian Lowland adjoining Altai; only far to the north, near the town of Kamen, in the Kolyvan–Tomsk folded zone, and along the northwestern margin of Kuzbass do the sediments of this extensive marine basin emerge from beneath the cover of the latest loose deposits. But the final resolution of a number of questions connected with marine transgressions into Altai and with faunal migrations is impossible at present, and will hardly be possible in the future, until more or less complete information is obtained on the geological composition of the basement of the parts of the West Siberian Lowland adjoining Altai.

For the convenience of the further exposition, we must briefly dwell on certain questions of the tectonic structure of Altai. In considering in the present study one particular question of the geological composition and geological history of Altai, we, of course, shall not set ourselves the task of illuminating from any new point of view, or of characterizing on the basis of already known materials, the general plan of the tectonic structure of Altai and its individual structural elements: we shall touch only upon those of them that have a direct bearing on the distribution of Devonian deposits and on the history of their formation. In this sense we shall first of all dwell on the most important, from our point of view, element of the Altai tectonic structure, which will appear repeatedly in our further exposition: I mean a fairly mobile zone that crosses the Gorny Altai from northwest to southeast, passing from the basin of the Anui and Peschanaya rivers through the basin of the Ursul River into the basin of the Chuya River; it is quite clearly expressed already on the map of Gorny Altai compiled by V. P. Nekhoroshev in 1927 and appended to the description of his route observations in Gorny Altai (Nekhoroshev, 1932). During the Devonian period this zone was characterized, in the main, by downward movements; it served as the principal route of Devonian transgressions into Altai, and the most important localities of faunistically characterized Devonian deposits of Altai are associated with it. We shall call it the Anui–Chuya trough, or the Anui–Chuya depression¹. The Anui–Chuya trough, at least during the Lower Devonian and in its northwestern part, had a geosynclinal nature and accumulated sediments of enormous thickness (p. 14). The Anui–Chuya depression has the character of a narrow strait, most constricted within Central Altai and somewhat widening—

…closing toward the southeast; but it opens especially widely to the northwest, in the direction of the Siberian Sea.

The northeastern margin of the Anui–Chuya downwarp is formed by the Kurai–Katun mountain system, which extends northward beyond the limits of the Altai. On the southwest this downwarp is bounded by the Tigirek–Belukha massif (Usov, 1936, p. 47); the northwestern continuation of the latter is the massif (probably less ancient) lying in the basin of the middle course of the Charysh River. Throughout the entire Devonian period, this Charysh–Tigirek–Belukha mountain system separated the Anui–Chuya downwarp from the shelf zone of Rudny Altai, beyond which, farther to the southwest, lay the Zaisan geosynclinal downwarp. On the other side, the Kurai–Katun mountain system separates the Anui–Chuya downwarp from that eastern depression which was mentioned above and which is a southward continuation of the Kuznetsk basin.

Let us pause preliminarily on one further question directly related to our topic. V. P. Nekhoroshev (1934; 1935) established the existence in the Paleozoic of the Zaisan geosynclinal basin, which at one time separated the epicontinental seas of Rudny Altai and Kazakhstan; the Zaisan geosyncline is quite definitely revealed from the Middle Devonian onward. We, however, consider its existence in still earlier times beyond doubt, since we disagree with V. P. Nekhoroshev’s opinion concerning the age of the metamorphic deposits of this geosyncline. This geosynclinal basin undoubtedly connected in the northwest with the Siberian Sea and played a major role in the Devonian history of the seas of the Sayan–Altai region. A very interesting analysis of the geological setting characterizing the Zaisan geosynclinal zone enabled V. P. Nekhoroshev (1935, p. 236) to establish that, in the Zaisan geosynclinal basin, we are dealing “with a deep downwarp (as is evidenced by the deposition of silty material that produced black shales), devoid of organic life, evidently because of insufficient ventilation of the depths of this downwarp by bottom currents, analogous to modern deep depressions deprived of connection with deep oceanic currents.”

One of the most important consequences of the Erian folding in the Altai was a decisive regression of the sea, which by the end of the Silurian period had freed from its cover almost the entire territory of the present-day Altai. Our information on the Gedinnian deposits of the Altai is very fragmentary, but we know that in the Gedinnian age, along the northwestern margin of the Altai, there was a marine basin, probably in the form of two gulfs—the Solovikha (Anui–Kuyagan zone) and Talovka (Rudny Altai) gulfs. These gulfs were connected with the open Siberian Sea; calcareous sediments were deposited in them. In the Talovka gulf coral reefs were widely developed, whereas in the Solovikha gulf living conditions were unfavorable not only for coelenterates (which are almost completely absent here), but also for other groups: this is indicated by the impoverished character of the fauna of the Solovikha limestone. Probably, parallel with the formation of the latter, to the east and southeast of the Solovikha gulf, in a lagoonal–continental setting, clayey shales of the lower part of the Kuyagan Formation were deposited; perhaps the moment of a short-lived expansion of the Solovikha gulf to the southeast coincided with the Gedinnian age as well, as a result of which we have a limestone interbed in the shale sequence of the Kuyagan Formation. The remaining territory of the Altai in the Gedinnian age probably constituted a mountainous region.

In the following Siegenian age we observe an expansion of the basin situated in the northwestern part of the Altai; however, this Siegenian basin is not a direct expansion of the Gedinnian one: between the Ge…

between the Dniestrian and Zigen ages, the northwestern part of Altai (and, perhaps, all of Altai) underwent a certain short-lived uplift. It entailed the regression of the Zhedin sea from the confines of Altai, and during the continental break that followed, the deposits of this sea were to a considerable extent denuded: the Zigen deposits (the Ganin Formation, the Zmeinogorsk deposits with the leptodontellid fauna, the formation that includes the Losikha limestone) lie directly upon older formations; moreover, for example, in the northern part of Rudny Altai this superposition of Zigen deposits on pre-Devonian rocks pertains to a territory that had previously been occupied by the Zhedin Talovka Gulf of the Siberian Sea. The Zigen transgression followed the routes of the Zhedin gulfs, and likewise the Zigen Altai basin is represented by two gulfs which (since they arose independently of the Zhedin ones) should be called by special names, for example—the Ganin Gulf and the Zmeinogorsk–Losikha Gulf.

We have traced the history of the Ganin Gulf fairly well. Initially, limestones were deposited in this gulf, but they were heavily contaminated by an abundant influx of detrital material; this latter circumstance had an unfavorable effect on the Bohemian-type fauna inhabiting this basin, which is usually found in purer limestones. When the influx of terrigenous material increased still more, and clastic (though also calcareous) rocks began to be deposited in the Ganin Gulf, this oppressed fauna was completely displaced by a new one, immigrating into the Ganin basin, evidently, from the confines of the Siberian Sea. The settlement of the Ganin Gulf by the new population proceeded gradually, and we are able to date precisely the moment (the perlamellose zone of the pseudotogatov time of the Zigen age) when the genus Leptodontella first appeared in it, accompanied by its usual associates (Leptaena bouei, Schuchertella altaica, Leiopecten rectangularis, etc.). Thus, in the Altai Lower Devonian sea there appeared a leptodontellid fauna, which was subsequently to play such an outstanding role. We do not know where this fauna arose and developed—probably somewhere farther north, within the Siberian Sea, in the territory now occupied by the loose cover of the West Siberian Lowland; but we can trace the subsequent history of this fauna fairly completely.

In the Zigen age the Ganin Gulf was a geosynclinal basin: this is indicated by the two-, and possibly even three-kilometer thickness of the Ganin Formation, consisting of the deposits of this basin. However, the Ganin Gulf was not a deep-water basin: the leptodontellid fauna, which flourished in this gulf, is an association of benthic organisms indicating a basin depth of no more than a few tens of meters. In pseudotogatov time the Ganin Gulf was broadly connected with the open sea; later it became shallow, reef-forming coelenterates settled in it in large numbers, and still later the shoaling of this gulf led to the formation, in its place, of lagoonal basins that already had only a very limited connection with the Siberian Sea. This, naturally, was accompanied by the emigration of the marine inhabitants of the Ganin Gulf, whose place in the newly arisen lagoonal basins was taken by a very peculiar, unique paramnigenian fauna (see p. 38), consisting almost exclusively of pelecypods.

We have grounds to suppose that, simultaneously with the deposition of marine and lagoonal rocks in the Ganin basin, to the southeast of it, within the present-day basin of the Peschanaia River, intense volcanic activity was taking place: here there accumulated effusive-tuffaceous rocks composing the upper part of the Kuyagan Formation. Another

The known center of extrusive volcanism of the Zigen age is Central Altai, in the vicinity of the village of Ongudai; here, likewise in a continental setting, there accumulated a pyroclastic-sedimentary sequence consisting of effusives of intermediate basicity and lilac-green sandstones and shales (the Ongudai Formation).

The Zmeinogorsk–Losikha bay was also inhabited by a leptodontellid fauna containing a number of forms common to the fauna of the Ganino bay.

It was pointed out above that by the end of the Zigen age the Ganino bay underwent radical shallowing. Analysis of other Lower Devonian formations of Altai shows that this shallowing was the first manifestation of a certain new phase of tectogenesis, which we have called the Ganino phase. We cannot at present say whether the manifestation of this phase was limited only to a simple upward movement of northwestern Altai and its desiccation, or whether it was accompanied by tangential diastrophism. In any case, between the Zigen and Lower Kobylen ages we established the presence of an interruption in sedimentation and of a continental regime, which was soon replaced by a new transgression of the sea, proceeding again along the old routes. This transgression is marked by a conglomerate at the base of the Kondrat’evka Formation. But within the Eodevonian we recorded yet another moment of manifestation of tectonic movements: the boundary between the Lower and Upper Kobylen ages is marked by a new desiccation of northwestern Altai and a new marine transgression, the deposits of which are represented by the Medvedevka Formation (p. 62), while the tectogenetic phase that preceded its deposition has been named by us the Kuyagan phase (p. 74).

A detailed study of the Kondrat’evka and Medvedevka formations allows us to give a bionomic characterization of the Lower Devonian basins of Northwestern Altai and to trace the history of the fauna that inhabited them. We shall note preliminarily that throughout the Eodevonian, beginning with the Zigen age, the marine basins that successively replaced one another retained certain common features: each time, rocks of one and the same character were deposited in them—thick sequences of predominantly clastic deposits, namely marly sandstones and shales and sandy limestones of greenish and yellowish-gray color; each time a leptodontellid fauna settled in them, preserving its general characteristics, although changing its composition; and the geosynclinal setting was also preserved, ensuring great thicknesses of these Lower Devonian formations: the total thickness of the Zhedin, Zigen, and Kobylen deposits of the given region is determined at a figure on the order of 7–8 km (this calculation does not include the effusive-sedimentary Kuyagan Formation). For the peculiar Lower Devonian deposits of the northwestern part of Altai, briefly characterized above and described in Chapter I, we apply the name Altai type of the Eodevonian (p. 13), and the geosynclinal region of their accumulation we call the Anui–Kuyagan geosynclinal zone.

We have traced above the history of the Ganino bay from its origin to its final freshening and shallowing. Before the freshening of the Ganino basin, the leptodontellid fauna that inhabited it emigrated, but later returned twice again to the limits of Northwestern Altai together with the return of the sea in the Lower Kobylen and Upper Kobylen ages. Each time, notable (at times considerable) changes occurred in the composition of the leptodontellid fauna, which will be considered by us below. But these changes could not entail the loss by this fauna of its basic features: it continued to remain endemic in its species (and partly also generic) composition, while at the same time containing a considerable number of forms closely vicariant with European and American species.

The composition of the leptodontellid fauna shows that the Kondrat’evka and Medvedevka basins possessed water of normal salinity and were not deep: the abundance of trilobites, and among them such typical benthic forms as dalmanitids (Probolium altaicum), the abundance of brachiopods and pleurodictyids, and the abundance and composition of pelecypods—all confirm this characterization of the Koblenzian basins of Altai. Of course, there were also known differences between the Kondrat’evka and Medvedevka seas; the former was somewhat deeper in those parts of it that are known to us.

The regime of these basins and the conditions of existence of the leptodontellid fauna are established most fully from analysis of the Medvedevka Formation, whose section we have studied in detail (pp. 62 ff.). In it one of the characteristic features of our fauna stands out with particular clarity—the uneven quantitative development of its components in general and their uneven distribution in the various beds of the section of the Medvedevka Formation; thus, in outcrop IX (Fig. 10) of this section, impressions of the valves of chonetid shells literally cover some bedding surfaces completely, leaving no free areas and partly overlapping one another. We can clearly picture for ourselves, on the floor of our Lower Devonian basin, a corresponding area covered with a layer of chonetid shells, which evidently lived as communities analogous to oyster banks. In similar fashion, on other bedding surfaces, mass accumulations are observed of impressions of shells of brachiopods, leptodontellids, spirifers, conchidiids, ctenodonts, and edmondiids; together with the chonetids we obtain seven genera that lived in masses on separate areas of the basin floor in which the rocks of the Medvedevka Formation were being deposited. Often in a single outcrop we observe a succession of forms developed in mass quantity in individual, often adjacent, beds; thus in outcrop X impressions of leptodontellid shells occur in masses, but in the lower part there is a bed filled with impressions of spirifer shells, and still lower—a bed with an equally large number of impressions of brachiopod shells; in outcrop IX, in its upper and lower parts, enormous numbers of impressions of chonetid shells are observed; but in one bed of the middle part chonetids are rare, whereas conchidiids occur in great quantity.

“In other words, almost every fauna-bearing bed possesses its own special, very simple biocenosis; these biocenoses often differ greatly even in two adjacent beds; some biocenoses appear several times in the section, but without any regularity or sequence that might lead one to suppose the presence of repetition of beds caused by tectonic reasons. From this we may conclude that the individual benthic forms in our basin formed communities, a kind of bank, consisting of one or two (more rarely, a larger number of) species; these communities migrated within the basin, apparently depending on changes in environmental conditions. In the linear vertical section of the sedimentary sequence there is revealed before us a picture of a certain area of the basin floor, occupied at different times by these various communities migrating within the basin. Thanks to such distribution of organisms during their existence and of their remains in the sedimentary sequence, the biocenoses of individual beds are only integral parts of the single fauna that inhabited the given basin, and not successive faunas replacing one another in the process of evolution or of colonization of the basin by way of repeated immigrations.

Accumulations of organic remains within each bed represent true biocenoses; the complete preservation of the shells that yielded the impressions, and the presence of opened but not disarticulated shells (Pseudaviculopecten limatus, Cleidophorus sibiricus, chonetids), undoubtedly indicate that the shells were buried at the place where the animals lived and were not subjected to post-mortem transport; the areas of the Medvedevka basin inhabited by our fauna did not have strong currents, and the bottom layers of water in them were not affected by surface agitation.” (Khalfin, 1940).

This basin, however, was not deep, at least at the beginning, when the lower, fauna-bearing part of the Med—

the Medvedevo Formation; this is stated quite definitely by the composition of the fauna. In this basin there took place intensified, complex, and variable sedimentation, which entailed, on the one hand, a motley alternation of terrigenous deposits of the basin, and, on the other, repeated migration within the basin of the biocenoses inhabiting it; precisely the unstable regime of sedimentation, subject to frequent fluctuations, is, in our opinion, the reason that induced the benthic inhabitants of the basin to undertake repeated resettlements within its limits. To complete the bionomic characterization of the basin, let us recall the coral and bryozoan limestones forming thin interbeds in the upper horizon of the fauna-bearing part of the Medvedevo Formation (p. 64); their presence and character make it possible to establish that in certain parts of this shallow-water basin there existed coral and bryozoan reefs, which were partly destroyed by surf, and fragments of colonies, falling to the bottom, were cemented by the terrigenous material being deposited.

The predominance in the upper part of the section under consideration of clayey rocks, completely devoid of organic remains, indicates that over time the regime of the basin changed radically. The characterization of the Medvedevo basin given above may, in its main features, be extended also to the Kondrat’evo basin.

Let us turn to consideration of the following question: the peculiarities of the leptodontellid fauna allowed me, even in my initial characterization of the Devonian of the Altai, to express the opinion that this fauna lived under conditions of substantial isolation (Khalfin, 1935).

In examining this question in greater detail, we shall try to clarify the nature of this isolation, i.e., we shall consider the question—did the leptodontella fauna live in an isolated basin, or is its isolation based on some other geographical circumstances? Against the first assumption (existence in an isolated basin) there are very weighty objections: by the character of development of its individuals, the leptodontellid fauna is normal, not only showing no features of an oppressed condition, but, on the contrary, compelling us to regard the conditions of its existence as optimal for the groups composing it. This is expressed both in its diversity, and in the mass quantitative development of its various components, and in the normal, usually large, sizes of individuals. Thus, dalmanitids (Probolium altaicum) reach 15 cm in length, while, for example, Crotalocephalus sternbergi is considerably larger than representatives of this species from the German Hercynian, the Carnic Alps, and Turkestan; our specimen of this species is, in its dimensions, comparable to the Bohemian (i.e., the largest) crotalocephalids. Likewise, Cheirurus strabo in our fauna is three times larger than representatives of this species from the Turkestan Eodevonian. Among our pleurodictyids there are not infrequent specimens whose corallites reach a centimeter in diameter, i.e., they belong to the largest among representatives of the genus Pleurodictyum. Our Tolmaia squamosa belongs to the group of the largest Devonian pterineids. The examples cited are all the more indicative because they are taken from various types of invertebrates and because Probolium altaicum, Pleurodictyum, and Tolmaia squamosa enjoy mass quantitative development in our fauna. In general, an abundance of large specimens of the forms composing it is characteristic of the leptodontellid fauna. It remains to add that all of them are typical marine organisms, and if optimal conditions existed for their existence, this means that the Nizhne-Devonian Altai basin, inhabited by the leptodontellid fauna, was a normal marine basin with normally saline water.

On the other hand, as was noted above and analyzed in detail in the description of the formations, within this fauna there are a number of forms identical with European and American ones, and an even greater number of forms undoubtedly related to them.

Thus, we arrive at the conclusion that the basin inhabited by the fauna of the Kondrat’evka Formation was a normal marine basin, and that this fauna, despite all its endemic character, in a number of cases shows connections with the European and North American fauna. This means that the Lower Devonian Altai basin at the time of deposition of the rocks of the Kondrat’evka Formation had a broad connection with the system of seas of the northern hemisphere, and the endemic character of the fauna of the Kondrat’evka Formation was not due to the closed nature of this basin. Nevertheless, there were certain barriers that hindered the free dispersal of the leptodontellid fauna. Along with the examples cited in their proper place (p. 57), showing that many components of this fauna have a genetic connection with European and American forms, our fauna also contains such groups for which no fairly close analogues can be indicated in the fauna of other regions and countries. These include, first of all, the genus Leptodontella, whose name we apply also to this entire fauna; likewise endemic is the genus Wilsoniella, with its exceptionally distinctive internal structure. Among pelecypods, similarly strictly local groups are the genera Myalinopterella and Ctenodontella. Evidently there were causes that did not allow these genera to pass beyond the limits of the Altai basin; in this respect, a comparison of our fauna with the Lower Devonian fauna of Kazakhstan is very indicative: there, under the same facies conditions, a different fauna is present (without Leptodontella and other endemic Altai forms). This fairly precisely determines the location of one of the obstacles to the dispersal of our fauna—namely, between the Western Altai and northeastern Kazakhstan. We believe that this obstacle was the Zaisan deep-water basin discussed above, whose isolating role for the fauna of the Middle Devonian and Lower Carboniferous had been established earlier (Nekhoroshev, 1935; Khalfin, 1938). There were also obstacles on the routes of communication between the leptodontellid fauna and the fauna of North America; we cannot yet say anything definite about them, but they too were not absolute, since some American forms proved capable of penetrating into our Altai basins.

Repeated migrations of the Lower Devonian fauna, now appearing in the Altai basins and now leaving them, led to the result that usually, in the composition of the fauna that returned again to a given basin, we each time find many entirely new components that had been absent from the fauna of the preceding basin. Somewhere beyond the limits of the Altai, the process of development of this fauna took place, interrupted repeatedly by invasions of various groups from the European and American seas. In the Altai Lower Devonian basins, however, we see only individual stages of this process, very weakly connected with one another; this creates the impression of the cryptogenic character of each fauna newly appearing in the Altai basin of one or another age. We observe only isolated forms that link the faunas of the different Eodevonian formations of the Altai; in Tables 24 and 25 are listed the identical and closely related forms by which the faunas of different horizons and formations are connected; the most important of these are the genus Leptodontella, the species Leptaena bouei and Cyrtina heteroclita.

With the passage of time, in the process of repeated migrations and exchange of populations with the seas of Europe and America, the geographical type of the leptodontellid fauna also changed; the principles for establishing the geographical type of the fauna and the geographical groups adopted by us are indicated above on

Table 24

Names of forms	Solovikhinsky horizon	Gania Formation: Rensselerian horizon	Gania Formation: Pseudotogatov horizon, Teniola zone	Gania Formation: Pseudotogatov horizon, Perlamellose zone	Gania Formation: Paraminigev horizon	Kondratyev Formation	Medvedev Formation
Atrypa supramarginalis	·······	·······
Levenea sp.-Leveneataeniolata		·······	·······
Leptaena bouei		·······	·······	·······		·······	·······
Cyrtina heteroclita		·······	?	·······		·······	·······
Leptodontella rotundata				·······		·······	·······
Atrypa lorana			·······	·······		·······	·······
Leiopecten rectangularis				—		·······

Table 25

Forms	Solovikhinsky horizon	Gania Formation: Rensselerian horizon	Gania Formation: Pseudotogatov horizon	Kondratyev Formation	Medvedev Formation
Atrypa supramarginalis	mut. α	mut. β	—	—	—
Genus Levenea	—	sp. indeterm	sp. taeniolata	?	sp. transversa
Brachyprion	—	—	aff. latus aff. naliwkini	sp. speranskii	sp. latus sp. naliwkini
Genus Leptodontella	—	—	sp. rotundata	sp. rotundata	sp. planuscula
Schuchertella altaica	—	—	forma typica	cf. forma typica	var. minor
Genus Chonetes	—	—	aff. rectispina	sp. rectispina	—
Deltchyris perlamellosa	—	—	forma typica	var. altaica	—
Nuculoidea lodanensis	—	var. altaica	sp. ex gr. N. lodanensis	var. altaica	—
Praemyophoria latifrons	—	—	forma praecedens	forma typica	—
Genus Tolmaia	—	—	sp. ex gr. T. squamosa	sp. squamosa	—

p. 21. In the description of each formation, a characterization of the geographic type of its fauna has been given; bringing all these data together, for the entire aggregate of the Lower Devonian faunas of northwestern Altai we obtain Table 26 (see next page).

From this table we see, in particular, that the quantitative ratio between European and American elements in the Lower Devonian fauna of Altai changes over the course of time. Thus, for example, the number of American elements in this fauna at first gradually increases, reaches a maximum in Pseudotogatov time, and then sharply decreases; this, of course, reflects certain paleogeographic features of the Eodevonian, not yet established by us, since we do not know the route by which faunal exchange took place between the Altai and North American seas. The change in the geographic type of our fauna is clearly shown in the diagram in Fig. 17.

Table 26

Horizons and formations	Eu	Am	En	Co	Total number of forms
Medvedev Formation	30% (4/19)	8% (0/6)	58% (44)	4% (0/3)	76
Kondratyev Formation	40% (5/26)	5.7% (0/4)	53% (41)	—	76
Paramonireev Horizon	—	—	90% (9)	10% (0/1)	10
Pseudotoryn Horizon	37.5% (3/6)	21% (2/3)	33% (8)	8.5% (0/2)	24
Rensselaeria Horizon	33% (4/4)	17% (1/4)	50% (12)	—	24
Solovikha Horizon	44% (7/5)	7.5% (1/1)	41% (11)	7.5% (0/2)	27

Parallel with the change in geographic type, the facies type of the Altai Lower Devonian fauna also changed, which is reflected especially clearly in the change in the ratio, within its composition, between elements of the Bohemian-Uralian (Hercynian) and Rhenish types (Fig. 18). In general, over the course of the Eodevonian there is a gradual transition of the Altai fauna

Fig. 17. Change in the geographic type of the fauna over the course of \(D_1\)
(for explanation of the indices, see p. 21)

from a purely Bohemian type (Gedinnian age) to an almost purely Rhenish type (Upper Koblenzian age).

Thus, the leptodontellid fauna characterizing the Eodevonian of the Altai type, despite all the changes noted above, continues throughout the entire Eodevonian to preserve an endemic species composition and a number of very distinctive features that sharply distinguish it from synchronous faunas

other regions and countries. We are entitled to conclude that it characterizes a certain Altai zoogeographic province of the Eodevonian.

The Eifelian history of the Altai is least known to us. If the Lower Eifelian age of the Tytkeskensk limestone and limestones developed near the village of Solov’yikha is confirmed, this will mean that the beginning of Eifelian time in the Altai was marked by a significant transgression, advancing from the Anui–Kuyagan zone to the southeast, into Central Altai. By this time, within southeastern Altai, in the basin of the Kara-gem and Chagan-Uzun rivers, a local depression had arisen which, probably in connection with the transgression just noted, became filled by the sea. This inner

Fig. 18. Change in the facies type of fauna during \(D_1\)

Kara-gem basin had limited communication with the Siberian Sea and in its character may have resembled the modern Black Sea; in it were deposited the black rocks of the Chagan-Uzun and Kara-gem formations, whose characteristics were given in the preceding chapter (p. 108). The subsidence of the Altai, with which the Lower Eifelian transgression characterized above is associated, was short-lived and, apparently still within the Eifelian epoch, was replaced by uplift, caused by some special phase of tectogenesis that is difficult to correlate with any of those previously established.

As a result of this uplift, the sea apparently completely left the territory of the Altai, and throughout the second half of the Eifelian and the first half of the Lower Givetian it was land, washed from the north and northwest by the Siberian Sea and from the southwest by the Zaisan geosynclinal basin; it is possible that for some time a relict Kara-gem lake-sea still existed. This entire interval of time in the Altai is characterized by very intense effusive activity. It is highly characteristic that this activity was confined mainly to certain parts of the Altai, which soon thereafter were filled by the sea. These are, first, the Anui–Chuya depression, along which the Lower Eifelian transgression had also developed; along this depression there was a series of centers of effusive volcanism, and in places (for example, in the Kurota graben) the thickness

the pyrogenic-clastic formations of this time reaches an enormous thickness (up to 4 km). Effusive activity was no less intense in the southwest, within the Rudny Altai; finally, a third area of intensive volcanism is associated with the territory of the Korgon Range, where the effusive Korgon Formation likewise reaches a thickness of 4 km. This volcanic cycle is characterized chiefly by acid varieties of effusives, although in places (for example, in the Anui–Kuyagan zone) it is also represented by more basic rocks. It is possible that at times, in some of the above-mentioned areas of effusive volcanism, brief marine incursions occurred; thus, apparently, such transgressions from the Zaisan geosyncline extended over part of the Rudny Altai; there are indications that the Kurota–Ursul effusive formation (p. 103) is also subaqueous and in some interbeds even contains marine fauna, i.e., it is possible that during the course of this volcanic cycle some brief marine ingression took place even within Central Altai. But, in the main, the effusive formations of this cycle have the character of subaerial formations, and the marine episodes we have noted are only secondary details in the history of Altai during the Upper Eifelian and Lower Givetian ages.

Within the Lower Givetian age falls the time of manifestation of a new phase of tectogenesis, which we correlate with the Telbes phase; its manifestation in Altai was also accompanied by intrusive volcanism, an example of which may be the intrusions of alkaline granites of the Kurota graben, which are genetically connected with the effusives of the cycle characterized above (Yu. A. Kuznetsov, 1939). The second half of the Lower Givetian age was marked by a certain local subsidence of the northern part of the Rudny Altai, where at that time a small bay arose, accumulating calcareous sediments that subsequently yielded the rocks of the Murzinka Formation. In Central Altai at this time, in places, there occurred an accumulation of red-colored continental deposits corresponding, probably, to the Antropovka and, possibly, Abramovka formations of Gornaya Shoria (p. 104).

A new important moment in the geological history of Altai corresponds to the Upper Givetian age: this age was marked by the most extensive of all Devonian transgressions of Altai. This transgression developed over the Anui–Chuya depression that had formed earlier, and the sea reached the headwaters of the Chuya River (Fig. 19): this Anui–Chuya sea is known to us quite well. In the west it formed two bays—the Korgon and the Terekta; it was inhabited by a chiyelian fauna and was characterized by a considerable diversity of facies (p. 93). Along its shores rose mountains created by the Telbes phase of tectogenesis.

The deepest-water part, naturally, was the northwestern part of this sea, from which the transgression began; the deposits of this part of the Anui–Chuya sea are predominantly clayey and constitute the Kuyagan facies of this basin (p. 93). The same facies (with minor variations) characterizes the axial part of the basin also within Central Altai; here, however, the mountains apparently approached the very shore of the sea, and brief pulsations of this part of Altai not infrequently caused the formation of conglomerates, which in places interbed here the clayey and calcareous sediments of the Anui–Chuya sea. Another facies type of sediments characterizes the Korgon bay and the southeastern part of this sea. These sediments are, in general, more shallow-water; limestones play a major role in them, and, moreover, in these parts of the sea—at least during the first half of the Upper Givetian age—waning effusive activity continued. The facies oscillations noted above are very sensitively reflected by the fauna inhabiting the Anui–...

sko-Chuya sea with fauna. These changes in the composition of the fauna, as well as a more detailed characterization of the fauna of the Anui-Chuya sea, are given in Chapter II, in the description of its deposits.

It is noteworthy that at the time when the Anui-Chuya zone of Altai underwent a significant subsidence and was filled by the sea, to the west, within the limits of Rudny Altai, no subsidence is observed: here Upper Givetian deposits with a chizel fauna are entirely absent. To suppose that they were completely destroyed here by denudation, or have not yet been discovered, is impossible, since nearby, in Gorny Altai, they have been preserved—

Fig. 19. Schematic geographical map of Altai for Upper Givetian time

—preserved in very many places and are known to us from a larger number of localities than any other Devonian deposits. We are justified in concluding that the formation in the central part of Altai of the Anui-Chuya trough was accompanied not by subsidence, but rather by uplift of the southwestern margin of Altai.

The boundary between \(D_2\) and \(D_3\) in Altai is marked by a very weak and transient upward movement (the Barzas phase of tectogenesis of M. A. Usov), which was immediately followed by a new subsidence, this time also involving the marginal parts of Rudny Altai. The uplift that took place at the very end of the Upper Givetian age led to the drying out of only some shallow-water marginal parts of the Anui-Chuya sea, for example, the Korgon Gulf (p. 94); apparently, the short-term drying also affected the

the southeastern part of the sea (p. 112). In its axial part, however, this movement was marked only by a rather abrupt change of facies at the boundary of \(D_2\) and \(D_3\) (p. 81).

The subsidence of Altai, coinciding with the beginning of the Frasnian age, restored the Anui–Chuya basin (Fig. 20), approximately within its former limits (with the exception of the Korgon Gulf); but this basin existed only during the Lower Frasnian time; its population was a typical suprasaliniferous fauna. Parallel to it, along the western margins of Rudny Altai, there were small gulfs sharply different from the Anui–

Fig. 20. Schematic geographical map of Altai for Lower Frasnian time

Chuya Sea. Thus, within the northern part of Rudny Altai there was a small gulf in which, along with limestones, black silty sediments were deposited, forming buchiolite shales similar to the Domanik deposits of the Urals; naturally, this basin too was inhabited by a fauna entirely different from the suprasaliniferous fauna. Farther south lay another gulf (the Nikolaevsk Gulf), which was characterized by an entirely different regime: here vigorous submarine outpourings of lava took place, alternating with short intervals of quiescence. These intervals of quiescence correspond to the deposition of limestones, now occurring as lenses among effusive-tuffaceous rocks. During such lulls in volcanic activity, the Nikolaevsk Gulf was populated from the Zaisan Sea by a diverse fauna, among which goniatites are especially characteristic—Manticoceras intumescens, Beloceras multilobatum, and others.

At the boundary between Early Frasnian and Middle Frasnian time, the marine stage in the history of the Altai Mountains comes to an end; corresponding to this is its general uplift and the final regression of the sea from its limits. This uplift took place within the Frasnian age and, clearly, corresponds to a certain special phase of tectogenesis, which we have named the Malafeev phase. Only Nikolayev Bay continued to exist after the general uplift of the Altai noted above; but from the limits of this bay, too, the sea apparently withdrew even before the end of the Frasnian age; in any case, in the Famennian age there was no sea at the site of Nikolayev Bay.

The final stage in the Devonian history of the Altai is represented by a transgression that came from the Zaisan geosyncline and embraced part of the Rudny Altai. The basin that arose here as a result of this transgression proved, in some of its parts, to be very stable and existed for a long time.

Judging from the composition of the fauna, it must be recognized that the Middle and Upper Devonian basins of the Altai (in contrast to the Lower Devonian ones) had broad communication with contemporaneous basins situated in other parts of the Sayan–Altai region. There is neither the possibility nor the need here to discuss questions of the Devonian geography of this entire region, but it should be mentioned that the connection noted above between the Altai basins and the basins of the Kuznetsk and Minusinsk depressions was effected through that extensive geosynclinal zone which received from B. F. Speransky the name of the Ob–Zaisan geosyncline, and within which the Zaisan syncline of V. P. Nekhoroshev constitutes one of the segments (the southwestern one). The Ob–Zaisan geosyncline bordered, from the west, northwest, and north, the complex Sayan–Altai continental mass during the Devonian period; separate segments of this geosynclinal zone are the Zaisan syncline, the Paleozoic deposits of the town of Kamen on the Ob River, and the Kolyvan–Tomsk folded arc. All the internal depressions of the Sayan–Altai region (Minusinsk, Kuznetsk, and Anui–Chuya) were connected with the Ob–Zaisan geosyncline, which also fed the repeated transgressions that invaded these depressions at different times. In accordance with the tasks set, we have traced the history during the Devonian period of only one of these depressions—the Anui–Chuya trough—touching only incidentally, when necessary, on the basins of the Rudny Altai, which were local bays of the Zaisan geosynclinal basin.

Such, in brief outline, is the history known to us of the Altai during the Devonian period. There is no doubt that further study of the Devonian deposits of the Altai and of the Sayan–Altai region as a whole will introduce many additions and corrections into the schemes of Devonian paleogeography and the history of the Altai that we have sketched.

3. Correlation of the Devonian of the Altai with deposits of other parts of the Sayan–Altai region

In proceeding to establish stratigraphic analogues of the Devonian formations of the Altai characterized by us in the preceding chapters, we must consider separately the question of correlating the latter with the marine and continental Devonian deposits of various districts of the Sayan–Altai region.

Marine Devonian deposits are most fully developed, apart from the Altai, along the margins of the Kuzbass, where they have also been studied sufficiently well. Therefore, naturally, the comparison of the Altai and Kuzbass Devonian deposits is of the greatest interest. This comparison is not equally easy to make for the deposits of the lower and upper halves of the Devonian: marine Devonian

deposits of Kuzbass, beginning with the Upper Givetian and higher, are well known to us. A sufficiently detailed subdivision of them is available for the northeastern and northwestern margins of Kuzbass, and the separate stratigraphic units are characterized by a fauna that has been studied quite fully (Tyazhnov, 1936; Khalfin, 1932; 1933; 1935; Khalfina, 1940). To this it must be added that, facially, they are often close to one or another of the Altai formations and are characterized by the same fauna (Chizhev and supraphacoidal faunas). Therefore we can without difficulty establish (Table 27) stratigraphically equivalent deposits of the northeastern and northwestern margins of Kuzbass and of Altai.

The situation is considerably more complicated with the lower half of the Devonian: these deposits, developed (in a marine facies) along the southwestern margin of Kuzbass (the northeastern margin of Salair), have been studied much less, and, as a rule, differ substantially in facies from the synchronous deposits of Altai. This applies especially to the Eifelian stage: even in the most recent summary on the Devonian of northeastern Salair by V. I. Yavorskii (1938), only facies (four in number) are indicated for the Eifelian deposits; but there is no doubt that these facies (at least in part) are not of the same age. Thus, there can hardly be any doubt that the facies of conchidium limestones belongs to a younger horizon than the facies of argillaceous limestones with Calceola sandalina. Likewise, the Lower Devonian of northeastern Salair is subdivided schematically, only into two stages—the “Gedinnian” and the “Coblenzian,” and their fauna has not been described and is known only from lists (Yavorskii, p. 1). These lists allow one to state with confidence that a more detailed study of the fauna will provide grounds for a more detailed subdivision of these deposits as well: within the “Gedinnian” stage of V. I. Yavorskii there are, apparently, both Gedinnian and Siegenian deposits; in exactly the same way, further studies must be assigned the task of subdividing the Coblenzian deposits of northeastern Salair into Lower and Upper Coblenzian. For the present, only a schematic correlation of the Eodevonian of Altai and Kuzbass can be given.

The correlation of the Altai Devonian with the deposits of the northeastern and northwestern margins of Kuzbass presented in Table 27 is sufficient also for the parallelization of the Altai Devonian with synchronous deposits of other regions of the Sayan-Altai region (in those cases, of course, where the fauna of the latter has been studied). Thus, it is evident that the Beisk formation of the western Sayan is equivalent to the Kyzylshin horizon of southwestern Altai, to the Belgebash and Kurota formations of Central Altai, etc. In exactly the same way, the Chingis suite of the Orda region (Kraevskaya, 1936) evidently corresponds to the Nikolaev horizon of Rudny Altai, etc.

Considerably more difficult is the parallelization with the Altai Devonian deposits of the continental Devonian formations, widely developed in some parts of the Sayan-Altai region. Difficulties here are of three kinds: first, difficulties arising from the sharp facies difference between the deposits being compared; second, difficulties due to the fact that the continental Devonian deposits of the Sayan-Altai region are very poorly characterized faunistically and floristically, and often are completely mute in the paleontological sense; third, the organic remains found locally in these deposits (eurypterids, ostracoderms, fishes, plant remains, mainly psilophytes) have either not been studied, or have as yet been studied very poorly, and usually date the corresponding formations only approximately. Therefore the correlation of the continental and marine Devonian deposits of the Sayan-Altai region, given in Table 27, cannot be regarded as final; and if, in general, it proves possible, this is only because the continental Devonian formations in some areas of their development have been subjected to detailed field and petrographic study. This applies first of all to the continental Devonian of Mountain Shoria (Usov, 1936; Baturin—

Table 27

Correlation of Devonian Deposits of the Sayano-Altai Region

Indices	Rudny Altai	Anui–Chuya trough of Gorny Altai	Northeastern margin of Kuzbass	Northwestern margin of Kuzbass	Northeastern Salair	Gornaya Shoriya	Minusinsk Basin and Western Sayan
DC	Tarkhan Formation	Absent	Upper red-colored unit	Upper red-colored unit		Absent	Minusinsk Formation
D₃²	Tarkhan–Ulba Formation	Absent	Pre-Longus horizon	Upper green shales. Limestone of Kosoi Utes		Absent	Turan Formation
D₃¹	Nadinikolaevskaya effusive Formation	Absent	Monstrous horizon	Intermediate unit	Absent	? Absent	Turan Formation
D₃¹	Nikolaev horizon	Absent	Middle red-colored unit	Glubokinsky limestone	Absent	Variegated unit	Turan Formation
D₃¹	Goniatite and buchiola horizons	Upper part of the Malayaevka and Chibit formations	Supraphalene horizon	Pozharishche unit. Lower green shales.	Absent	Supraphalene horizon	Turan Formation
D₂³	Kokuiskaya effusive-tuff Formation	Lower part of the Malayaevka and Chibit formations; Korgon–Elovskaya, Belgebash and Kurota formations	Lower red-colored unit	Sandstones of the village of Askol’d	Absent	Sandstones with Bothrodendron	Beisk Formation
D₂³	Kuryinsk limestone; Murzinsk Formation	? Abramovka Formation	Barzas Formation	Chizhel horizon (beds with Spirifer cheehiel—Lebedyanskaya Formation)	Absent	Absent	Beisk Formation
D₂³	Kuryinsk limestone; Murzinsk Formation	? Abramovka Formation	? Effusive-tuffaceous unit of the Barzas district		Absent	Abramovka and Karatag formations?	Pechenovka Formation
D₂²		Antropovka Formation			Indospirifer horizon	Antropovka and Orton formations	Tashtyp Formation
D₂²		Antropovka Formation	Absent		Haskotrilos horizon	Upper unit of the Telbes Formation (after M. A. Usov)	? Pyrenean beds
D₂¹	Effusive-tuffaceous unit	Effusive-sedimentary formations: Korgon, Belgebash–Chuya, Kurota–Ursul	Absent		Unsubdivided stratigraphically Eifelian deposits: a) with tentaculitids, b) with Conchidium pseudobaschkiricum, c) with brachiopods, d) with Calceola	Lower unit of the Telbes Formation (after M. A. Usov)	Beds with “Aza fauna”
D₂¹	Akimovka Formation	Eifelian limestones of the Kurota and Anui–Gany grabens; Chagan-Uzun and Karagem formations	Dmitrievsko-Pereboi unit		Pester limestone	Absent?	Abakan Formation
D₂¹	Akimovka Formation	Eifelian limestones of the Kurota and Anui–Gany grabens; Chagan-Uzun and Karagem formations	Krasnogorsk unit		Pester limestone	Absent?	Abakan Formation
D₁³	Unsubdivided deposits with Leptodontella fauna; Batun Formation; Ridder Formation	Medvedevka Formation	Absent?		Krekov limestone	Absent?	Abakan Formation
D₁²	Unsubdivided deposits with Leptodontella fauna; Batun Formation; Ridder Formation	Kondrat’evka Formation	Absent?		Krekov limestone	Absent?	Abakan Formation
D₁¹	Kuryinsk–Loktevsk and Lyosikhinsk limestones	Gany marine and Ongudai continental-effusive formations	Absent?		Ostracod horizon (in part)	Absent?	Abakan Formation
SD	Talov limestone	Solov’ikhinsk limestone	Absent?		Ostracod horizon (in part)	Absent?	Abakan Formation

1936; Radugin, 1936): this subdivision was carried out so successfully that the corresponding formations, as typical ones, even entered the summary tectono-stratigraphic scheme of Siberia compiled by M. A. Usov (1936, table II). However, the age of these formations is determined differently by different authors; thus, V. S. Baturin (1936) assigned the Telbess Formation to the Lower Devonian, while M. A. Usov (1936) raised it to the Givetian Stage. On the basis of the presence, in the lower part of this formation, of the Protolepidodendron horizon, and in the overlying Antropovsk Formation of remains of Hostimella and Asteroxylon elberferdense, we accept the age of these formations as lying within the Eifelian and lower Givetian stages. This also determines the correlation of other continental formations of Gornaya Shoria and the outskirts of Kuzbass with marine deposits, in particular with the marine Devonian of Altai (Table 27).

For the reasons set forth in Chapter II (pp. 100, 103), we accept that the effusive-sedimentary Middle Devonian formations of the Anui–Chuya depression (the Korgon, Kurota–Ursul, and Belgebash–Chuya formations) correspond to the upper suite of the Telbess Formation.

Correlation with the Devonian deposits of the Western Sayan and the Minusinsk Basin is given chiefly in accordance with the new subdivision of the continental strata of these regions proposed by A. G. Sivov.

4. Tectono-stratigraphic scheme of the Devonian of the Sayano-Altai region

The most recent stage in the development of the stratigraphy of the Sayano-Altai region begins with the classic work of M. A. Usov on the phases and cycles of the tectogenesis of Siberia (1936); this work was not only a critical generalization of all the materials on the geology of Siberia that had accumulated by the time of its publication, but also defined new paths and methods in the elaboration of stratigraphic questions. This work will forever remain a monument of bold creative innovation, energetically advancing Soviet geological science. But this does not mean that the scheme of Siberian stratigraphy proposed by M. A. Usov was complete in all its parts and did not require detailing and expansion; a simple review of this scheme (Usov, 1936, table II) shows that the materials at M. A. Usov’s disposal when it was compiled differed in the degree of their detail and reliability. This, of course, was reflected in the degree of detail of the various parts of the stratigraphic scheme proposed by M. A. Usov, as well as in the selection of the formations which, as typical ones, entered into this scheme. What has been said is illustrated very clearly by that part of M. A. Usov’s scheme which pertains to the Devonian system; here we see, first, that of the 8 Devonian formations taken into account by M. A. Usov’s scheme, 5 fall in the Middle Devonian and 3 in the Lower and Upper. Moreover, the formations that entered this scheme as typical ones were not marine formations, usually richly characterized faunistically, but continental deposits, partly mute in paleontological respect, the very age of which was (and even now is) insufficiently determined. All this is explained only by the fact that, at the time this scheme was compiled, the Middle Devonian of Siberia, and specifically the continental Middle Devonian, had been subdivided more satisfactorily than the Lower and Upper.

Corresponding to the number of formations, the number of phases of Devonian tectogenesis in M. A. Usov’s scheme is 7; of these, 4 fall in the Middle Devonian; within the Eodevonian one phase is noted, and in the Upper Devonian—none. Of course, with the expansion of our knowledge of the composition and character of the Devonian deposits of Siberia we are establishing new formations which are absent from M. A. Usov’s scheme and which were not known or

were insufficiently known when this scheme was being compiled; new breaks in sedimentation are also being established, corresponding to phases of tectogenesis that had not previously been known. In particular, our study of the Devonian deposits of the Altai has made it possible to subdivide the Devonian system of Siberia in greater detail than had been done before. This applies first of all to the Lower Devonian, within which (including also the Gedinnian deposits) no fewer than four lithologically diverse groups of formations are distinguished in the Altai, separated by tectono-denudational breaks; therefore I considered it possible to attempt to give a more detailed stratigraphic scheme of the Devonian of the Sayan-Altai region (Table 28) than the scheme of M. A. Usov.

Table 28

Phases of tectogenesis	Marine formations and horizons	Indices	Continental formations	Phases of tectogenesis
? >	Tarkhan Formation	DC	Minusinsk Formation
? >	Prelongus Horizon	D₃²	Turan Formation
Nikolaevskaya >	Monstrovyi Horizon	D₃¹	Turan Formation
Nikolaevskaya >	Nikolaevskii Horizon	D₃¹	Turan Formation
Malafeevskaya >	Supraphalenovyi Horizon	D₃¹	Turan Formation
Malafeevskaya >	Chizhevo Horizon	D₂³	Barzas Formation	< Barzasskaya
Malafeevskaya >	?Kura limestones	D₂³	Abramovskaya Formation	< Abramovskaya
Malafeevskaya >	?Indospirifer Horizon	D₂²	Antropovskaya Formation	< Antropovskaya
Malafeevskaya >	Khaskotyris Horizon	D₂²	Upper member of the Telbes Formation	< Telbesskaya
Malafeevskaya >	Limestones with Conchidium pseudobaschkiricum; limestones with Calceola sandalina	D₂¹	Lower member of the Telbes Formation	< ? Akimovskaya
Medvedevskaya >	Medvedevskaya Formation	D₁³	Abakan Formation
Kuyaganskaya >	Kondratyevskaya Formation	D₁²	Abakan Formation
Ganinskaya >	Ganinskaya Formation	D₁¹	Abakan Formation
Solovykhinskaya >	Solovykhinskii limestone	SD

At the same time, I was faced with the natural question of selecting, from a large number of synchronous formations, those that could be adopted as typical and enter into the composite stratigraphic scheme. In resolving this question, I sought to include in my composite stratigraphic scheme of the Devonian of Siberia those formations and horizons that are most fully characterized paleontologically and whose fauna is

is the best studied. In the preceding exposition it has been noted more than once that, in this respect, not all divisions and stages of the Sayan–Altai Devonian have been studied to an equal degree; therefore, in our scheme (Table 28), alongside the Lower and Upper Devonian marine formations and horizons, whose fauna has been studied in detail and described monographically, there is a series of Middle Devonian horizons (Eifelian, Khaskotyris, Indospirifer, Kurya coral limestones), about whose fauna we can judge chiefly from more or less substantial lists of forms cited by various authors. Naturally, this very part of our scheme, insofar as marine formations are concerned, is the least studied also with respect to tectonic phenomena; fortunately, this gap is to a considerable extent filled by the fact that precisely the Middle Devonian continental deposits have been examined most thoroughly from this point of view—it was in these deposits that the most important phases of the Telbes tectogenesis were first established and recorded (Usov, 1936).

In compiling a summary stratigraphic scale of the Devonian of the Sayan–Altai region, I considered it necessary, parallel with the column of marine deposits, to present also the stratigraphic succession of the continental Devonian formations, which are so widely distributed among us. It goes without saying that, in correlating marine and continental deposits, we encounter a number of difficulties, of which we have already spoken above. The age of our continental formations and horizons is established without difficulty only in those cases where they are interbedded with marine, faunistically characterized deposits, as occurs, for example, along the northeastern margin of the Kuzbass: there the position of three red-colored sequences of different ages is rigidly fixed by the marine horizons separating them (see Table 27). As typical continental formations we introduce into our scheme, first of all, the Gornaya Shoria formations for the following reasons: a) they are the best studied in terms of their stratigraphic subdivision and the establishment of the individual features of separate formations; b) in the literature of recent years the practice has already become established of comparing the continental Devonian deposits of various districts of the Sayan–Altai region with the Gornaya Shoria formations; c) finally, guided by the rule of priority, these formations must be given preference over others, since they already figured in the scheme of M. A. Usov. However, all these formations (with the addition also of the Barzas Formation), in our opinion, fit within the limits of the Middle Devonian (Table 28): “the Devonian history of the district¹ begins with deposits of the Telbes Formation” (Usov, 1936, p. 127), to which M. A. Usov assigned a Givetian age. In part, such an age determination for the Telbes Formation was based on its comparison (Usov, loc. cit., p. 140) with the Minusinsk deposits now distinguished by A. G. Sivov as the Pechenovo Formation, which should be correlated with the Abramovo Formation of Gornaya Shoria (Table 27). But in addition, the presence of remains of Protolepidodendron in the lower part of the Telbes Formation, and the relationships accepted by us (p. 104) between the Tytkeskenskii Horizon and the analogue of the Telbes Formation in the Kurota graben of Altai—the Kurota–Chuya Formation—compel us to leave the Telbes Formation in \(D_2\), lowering its age to Eifelian–Givetian. However, we see no grounds for considering this formation Lower Devonian (Baturin, 1936).

Thus, only for the Mesodevonian does it prove possible to make use of the detailed subdivision of continental formations carried out by M. A. Usov and S. A. Baturin. As for the Lower

¹ Telbes.

and Upper Devonian, then for them we must still await the appropriate studies, which, evidently, should be carried out chiefly on the material of the Minusinsk Devonian. In general, the detailed stratigraphic subdivision of the Devonian deposits of the Minusinsk Basin is a matter for the future, and “until the entire Minusinsk fauna has been fully critically reworked, it will be more correct to refrain from categorical conclusions on this question” (Edelstein, 1932, p. 27). Therefore, not counting the new detailed observations of A. G. Sivov, which likewise relate only to the Middle Devonian, in our summary scheme for the continental facies of the Lower and Upper Devonian we can indicate only, for the time being, the strata not yet subdivided into formations—the Turan suite \(D_3\) and the Abakan suite \(D_1\). In general, the question of the continental Lower Devonian of the Sayan–Altai region requires very careful study and is unlikely to find its solution without paleontological substantiation. Of course, we also do not consider the question of the age of the Telbes formation to have been finally resolved.

In our stratigraphic scheme of the Devonian of the Sayan–Altai region we distinguish no fewer than eleven (probably no fewer than thirteen) phases of tectogenesis. In its proper place (see p. 74) we indicated why, in naming them, we avoid using the names accepted for the phases of Telbes tectogenesis in Western Europe. Here it is necessary only to dwell on the question of the possible character of the tectonic movements corresponding to these phases. These movements, quite evidently, had different characters at different moments in the Devonian history of the Sayan–Altai region; at times they represented only oscillations, simple and often short-lived uplifts, which, however, in separate parts of the Sayan–Altai region created conditions that ensured interruptions in sedimentation and denudation of formations deposited earlier. Such uplifts had a local character and entailed local regressions of the sea; examples are provided by manifestations of the Barzas phase of tectogenesis in the Altai: there it drained the Korgon gulf of the Anui–Chuya sea (p. 94), and caused the erosional break between the lower and upper parts of the Chibit formation (p. 112), but, for example, in the Anui–Chuya geosynclinal zone it could not have produced a break in the accumulation of sediments and was reflected only in an abrupt change of facies at the boundary between the lower and upper parts of the Malafeev formation (p. 81). The tectonic phenomena of the Telbes phase, which, as has been clarified by the studies of M. A. Usov, in particular, were accompanied by intrusive volcanism, just as was the Abramov phase, had an entirely different character; with one of these phases is connected, for example, the intrusion of alkaline granites of the Kurota graben of Central Altai (p. 105). To establish the character of the tectonic movements of each of the phases of the Telbes cycle would require an analysis of the relevant materials for the entire Sayan–Altai region, which lies far beyond the tasks set by me in the present work.

In concluding the presentation of the remarks that I wished to make concerning the stratigraphic scheme of the Devonian of the Altai proposed in this work (Table 28), I emphasize once again that this scheme is based on materials developed to varying degrees and reliable to varying degrees. Therefore we shall regard our scheme only as one of the first approximations to a detailed stratigraphy of the Devonian deposits of Siberia; further elaboration of this scheme, and refinement of the stratigraphic position of its individual members, will evidently be necessary as new materials on the geology of the Sayan–Altai region accumulate.

Necessary Corrections

Page	Line	Printed	Should read
65	3 from bottom	From the footwall side of the formation	From the lower faunistic layer
118	3 from bottom	Atryura undata	Athyris undata
183	21 and 28 from bottom	Stuart	Stewart
207	13 from top	length—l      width—d	width—d      length—l
208	20–21 from bottom	Ventral margin	Anterior margin
210	10 from top	Maryland	Pennsylvanian
215	11 from top and 1 from bottom	1933	1933 a
219	14 from top	the epoch was changing	the epoch is noted
241	2 from bottom	1933	1933 a
258	25–26 from top	anterior pair	posterior pair
259	18 from top	Lept. planuscula	Lept. acuta
261	15 from top	XXVII	XVII
270	14 from bottom	1888	1867
294	8 from bottom	1880	1880 a
320	26 from top	Leptodontella planuscula	Leptodontella rotundata
321	8–9 from top	of a round sector	of a circular sector
326	8 from top	1915	1909
332	1 from bottom	1894	1884
337	14 from top	less fundamental	less substantiated
339	27 from top	1933	1933 a
344	14 from top	sufficient	sufficiently
349	25 from top	broad field	broad posterior-upper field
357	12–13 from top	radial ribs	concentric ribs
357	13 from bottom	in front of the apices	behind the apices
361	17 from bottom	in width	in height
366	21 from bottom	very deep	very coarse
394	16 from top	homologous	homological
414	2, 11, and 42 from bottom	1934 a	1934
414	18 from top	1934 v	1934 a
429	1, 11, and 16 from bottom	1900	1900 a
430	15 from top	1900	1900 a
436	26 from bottom	in width	in height
451	11 from bottom	1899	1892
457	12 from bottom	fig. 11–14	fig. 7, 11–14
459	18 from bottom	p. 281	p. 264
462	1 from top	XXIII	XXVIII
462	9 and 12 from bottom	p. 438	p. 433
464	4 from top	p. 912	p. 351
464	7 from top	p. 915	p. 352

1. This very name was applied to this structural element of Altai by V. A. Kuznetsov in an article published in 1941 in the Bulletin of the West Siberian Geological Administration. ↩↩↩↩↩↩↩↩

2. Izvestiya Zap. Sib. filiala AN SSSR, geological series, 1946, issue 1. ↩