NEW DATA ON THE STRATIGRAPHY OF THE PALEOZOIC OF THE NORTHERN PART OF THE KUZNETSK ALATAU

V. D. Alimova, B. D. Vasiliev

(Presented by Prof. Dr. A. G. Sivov)

This article, which is preliminary in character, considers the stratigraphy of Cambrian deposits, most of which were previously regarded as Devonian.

The area where the Kuznetsk Alatau joins the Chulym-Yenisei Meso-Cenozoic trough [6], in the section where the Kiya River emerges from the Kuznetsk Alatau near the village of Chumai, has been studied geologically rather poorly. The reason for this is the wide development of Meso-Cenozoic deposits, the low degree of exposure under weakly dissected relief, and the earlier view that this area was unpromising for mineral resources. The low-mountain relief of the Kuznetsk Alatau, approximately 7 km south of the village of Chumai, gives way to hilly relief, which, in turn, north of the Chumai River passes into a plain. Paleozoic sequences are exposed in zones of low-mountain and hilly relief, whereas the plain is composed of Cretaceous deposits.

Within the Paleozoic sequences of the area, the greatest distribution is enjoyed by effusive rocks of basic and acidic composition, often in a diagenetic state, terrigenous variegated rocks, and limestones with archaeocyathid fauna. During medium-scale geological surveys, A. R. Ananyev (1940), T. M. Dembo (1947), and L. V. Alabin (1959) assigned the limestones with archaeocyathid fauna to the Cambrian, and the volcanogenic-terrigenous formations to the Devonian and, on this basis, explained the structure of the area (Fig. 1). D. V. Nikitin (1940) dated these sequences respectively as \(Cm_{1+2}\) and \(Cm_{2+3}\).

In 1963 and 1964, in this area, during educational geological field practice, students of the Tomsk Polytechnic Institute, under the supervision of B. D. Vasiliev, carried out geological survey work. Taking into account the exposure conditions in each specific case, geological mapping was carried out at scales of 1:10000 and 1:1000, with tracing of individual marker horizons along strike and with complete outlining of exposed areas. The survey was accompanied by searches for and collection of organic remains. The material obtained during these surveys radically changes the existing conception of the age of the rocks and the tectonic structure of the area (Fig. 2).

First of all, it was established that the limestones with archaeocyathid fauna do not have an areal distribution, but compose only beds and lenses in a terrigenous sequence made up of variegated graywackes and sandstones, often conglomeratic. Among the variegated rocks there are horizons of red-colored sandstones.

Fig. 1. Schemes of the geological structure of the Chumai area according to D. V. Nikitin (I), A. R. Ananyev (II), T. M. Dembo (III), and L. V. Alabin (IV): 1 — Quaternary deposits; 2 — loose rocks of the Mesozoic platform cover; 3–4 — volcanogenic-sedimentary rocks: 3 — predominantly volcanogenic, 4 — predominantly terrigenous; 5 — carbonate rocks; 6 — granitoids; 7 — disjunctives; 8 — points with fauna.

Fig. 2. Schematic geological structure of the Chumai district after B. D. Vasiliev:

Visible map/profile labels: A—B; Chumai River; Kiya River; K-I, K-II, K-III, K-IV, K-V; sample/locality numbers 12, 15, 28, 37, 43, 45, 48, 50, 51, 52, 53, 55.

The terrigenous sequence extends westward from the mouth of Krivoy Chumay as a belt of submeridional strike up to 2 km wide and has been traced along strike for a distance of 8 km. Individual marker limestone horizons within it have been traced discontinuously along strike for distances of up to 2.5 km, with insignificant thickness, which practically excludes the possibility that they are of redeposited origin. The entire sequence lies relatively gently, with an overall dip to the west-northwest at angles of 40–55°, the most persistent dip angles being 48–50°. The incomplete thickness of the terrigenous sequence in the Chumay basin is determined from the section to be 1500 m. The largest limestone members in it do not exceed 150 m in thickness. The greater resistance of the limestones to physical weathering, in comparison with the terrigenous rocks, has caused a distinct dependence of the relief on the geological structure: positive relief forms are composed of limestones, depressions of terrigenous rocks. Mapping by bedrock outcrops during medium-scale surveying, A. R. Anan’ev, T. M. Dembo, and L. V. Alabin naturally made an error, showing an areal distribution of Cambrian limestones in the Chumay basin. D. V. Nikitin assumed that the more ancient limestones of $Cm_{1+2}$ crop out in the closures of narrow anticlinal folds from beneath the terrigenous sequence $Cm_{2+3}$ and thereby considerably complicated the structure of the area.

The terrigenous sequence with limestone members has been characterized faunistically at two horizons. The lower faunistic horizon is situated 300 m above its base, has a thickness of 50–60 m, and is represented by organogenic limestones (areas K-II, K-IV), from which, in collections by B. D. Vasil’ev, V. D. Alimova identified archaeocyaths: Tersia sp., Protopharetra sp., Cyclocyathellidae. From the same place V. A. Shipitsyn identified algae: Epiphyton fasciculatum Chapm., E. aff. fruticosum Vologd., Girvanella sp. In addition, small brachiopods, gastropods, trilobite segments, hyoliths, and stromatoporoids also occur here.

The upper stratigraphic horizon is situated 1200 m above the base of the sequence and is represented by the Karacharovo limestones proper, 120–150 m thick (areas K-I near the village of Karacharovo and K-III at the summit of Pryamoy Chumay). From collections by B. D. Vasil’ev from the limestones of area K-I, N. A. Aksarina identified Kutorgina sp. V. D. Alimova identified archaeocyaths: Batchatocyathus kazakevitsi Vologd., Asterocyathus salairicus Vologd., Dictiocyathus salairicus Vologd., Salairocyathus sp., Protopharetra cf. grandicaveata Vologd., Docidocyathus sp., stromatoporoids. V. A. Shipitsyn identified algae: Epiphyton fasciculatum Chapm., Epiphyton aff. fruticosum Vologd., Razumovskia sp.; and from detrital limestones of area (K-III), respectively, Dokidocyathidae, Cribrocyathus sp., Coscinocyathus sp., Salairocyathus sp., Uralocyathus sp., Epiphyton sp., and a number of new forms.

North of Karacharovo (K-Iᵃ), from collections by D. V. Nikitin [7], A. G. Vologdin identified Tersia sp., Protopharetra sp., close to Protopharetra lata Born., and also algae: Epiphyton fasciculatum Chapm., E. fruticosum Vologd., Marpolia sp.

The effusive sequence, assigned by A. R. Anan’ev, T. M. Dembo, and L. V. Alabin to the Devonian, is exposed west of the village of Chumay on Mount Bukhtay, then at the mouth of Krivoy Chumay, on the watershed of the Chumay and Usek, and on the left summit of the Usek, i.e., as a belt of submeridional strike 1.7 km wide directly east of the outcrops of the terrigenous sequence. The effusive sequence dips to the WNW at angles of 43–52°, which is clearly visible on Mount Bukhtay from the pyroclastic horizons. The lower stratigraphic position of the effusive sequence in relation to

to the terrigenous unit is confirmed not only by the elements of occurrence (structurally), but also by the presence within the terrigenous sequence of products of erosion of the effusive sequence: the rocks of the terrigenous sequence and the beds of archaeocyathid limestones within it contain, along with other erosion products, numerous water-clear quartz grains characteristic of the quartz-bearing rocks of the volcanogenic sequence.

The effusive sequence is about 1200 m thick and is composed, from bottom to top, of pyroxene and plagioclase porphyrites, often quartz-bearing, with horizons of pyroclastics and with volcanic bombs on Mt. Bukhtai (about 300 m thick), of quartz and quartz-free albitophyres (about 200 m thick), greenstone porphyrites and, in the upper part, characteristic amygdaloidal rocks. The amygdules in the latter reach the size of a hen’s egg and are filled with chalcedony. The horizon of amygdaloidal rocks is clearly traceable along the strike, crowns the section of the effusive sequence, and is directly overlain by graywackes of the terrigenous sequence. Taking into account the stability (persistence) of the boundary horizons of the effusive and terrigenous sequences, as well as the similar elements of their occurrence, one may speak of the absence of structural unconformity between them.

The rocks of the effusive sequence of the Chumai area are characterized by a high content of free silica in the form of quartz and chalcedony, which sharply distinguishes it from the other volcanogenic suites of the Mariinsk taiga. The relative freshness of the rocks, the diagenetic state of many of them with cherry-colored tones, and also the increased acidity of the rocks served previous investigators of the area as a basis for assigning these volcanogenic formations to the Telbes Series of the Devonian. We have shown above that the effusive sequence of the Chumai area lies stratigraphically below the terrigenous sequence with horizons of archaeocyathid limestones and, consequently, can be only Cambrian in age.

Stratigraphically below the effusive sequence, in the middle course of the Usek River, occur coarse- and fine-pebble conglomerates containing horizons of lavas of pyroxene porphyrites with pebbles of limestone, porphyrites, and intrusive rocks incorporated in them. The latter are represented by flesh-red coarse-grained granites and syenites. Similar conglomerates and “lava-conglomerates” are exposed on the side of the Kiya River valley near the settlement of Smirnovskii and below the mouth of the Chumai (Mt. Bukhtaichik). They were formerly assigned to the Devonian.

The section along the Kiya River from the settlement of Smirnovskii to the mouth of the Chumai is structurally more complex than the western part of the area, where we had one limb of a large structure, dipping WSW (260—290°) at angles from 40 to 55°. In the section along the Kiya River, dips of easterly bearings predominate, more often ESE 110—125°, more rarely NE 30—60°, with dip angles of 8—15°. Thus, here we have the eastern limb of an anticline, complicated by gentle subsidiary folds.

The Smirnovskii conglomerates are exposed by the Kiya River diagonally to their strike above the mouth of the Smirnovskii stream. It should be clarified: the conglomerates proper are exposed only in the middle part of this section, over a distance of about 120 m (from 900 to 1020 m above the mouth of the Smirnovskii stream). They dip NE 25° at angles of 37° and contain boulders of pink porphyritic granites, syenites, and various effusive rocks.

Stratigraphically above the normal conglomerates lie “lava-conglomerates,” consisting of lavas of coarse-porphyritic pyroxene porphyrites with numerous pebbles of various

composition and size. They are interbedded with packets of diagenetized litho-crystalloclastic tuffs of pyroxene porphyrite. As a rule, the pebbles are well rounded, but occasionally large blocks (more than 1 m across) of limestone are encountered, and even a stratified horizon 3–4 m thick composed of limestone blocks of various sizes. The limestones are organogenic; their white and gray varieties consist chiefly of algae, whereas those unevenly colored in greenish and cherry-red tones consist of archaeocyaths, brachiopods, trilobites, and algae.

From one block of organogenic limestone measuring \(1.0 \times 0.6\) m, enclosed in a pyroxene “lavoconglomerate” on the left side of the valley of the Kiya River, 820 m above the mouth of the Smirnovsky Brook (K–V section), trilobites Erbia sp., Edelsteinaspis sp., Kootenia sp. were preliminarily identified from collections by B. D. Vasil’ev by I. I. Koptev; B. D. Alimova identified archaeocyaths Erbocyathus heterovallum Vologd., Vologdinocyathus sp., Archaeocyathus cf. erbiensis Zhur., Ethmophyllum cf. ratum Vologd. V. A. Shipitsyn identified the algae Renalcis granosus Vologd., Epiphyton retiforme Korde, Epiphyton cf. fasciculatum Chapin., Girvanella sp.; brachiopods are also present here. The faunal assemblage listed above is close to the Obruchev assemblage of the Sayan–Altai region [8].

Stratigraphically below the normal conglomerates lie dark-green pyroxene porphyrites, formerly assigned by A. R. Anan’ev to the Cambrian. They are also in contact with the Kozhukhovsky granite-diorite massif in this section. The character of the contact remains unclear: on the one hand, both the effusives and the tonalites bear traces of cataclasis, are broken in the contact zone by numerous slickenside planes, and are intensely destroyed, in connection with which a narrow ravine has formed along the immediate contact; on the other hand, the tonalites of the Kozhukhovsky massif in the contact zone are characterized by variability of textural features and by the presence of schlieren-like segregations of more basic composition, and this may indicate the marginal facies of the intrusive massif. In any case, the available material contradicts the opinion of L. V. Alabin [1] that the Smirnovsky conglomerates overlie the intrusive rocks of the Kozhukhovsky massif: the strike of the conglomerates is almost perpendicular to the strike of the massif contact line in this area, and therefore the relationships may be regarded either as disjunctive or as magmatic (breakthrough). The latter is most probable, taking into account the overall anticlinal structure of the area and the transverse position of the Kozhukhovsky massif with respect to it. The effusive rocks of the near-contact zone, occurring stratigraphically below the normal conglomerates, are, as noted above, pyroxene porphyrites, but cataclasis and hydrothermal alteration give them a greenstone appearance.

Finally, stratigraphically below the sequence of conglomerates and “lavoconglomerates,” on the right side of the valley of the Kiya River opposite the mouth of the Usek Brook, a sequence of yellowish fine- and small-grained arkosic sandstones, tuffaceous sandstones, and acid effusives of variolitic texture occurs in a small cliff. They dip at an angle of \(15^\circ\) to the SE, beneath the conglomerate sequence. Their incomplete thickness is about 150 m.

The material set forth above allows us to draw the following conclusions. In the northern part of the Kuznetsk Alatau, in the area of the Chumai River, deposits previously assigned to the Telbes Series of the Devonian have a faunistically proven Cambrian age. They are gathered into a large anticlinal fold of submeridional strike, which

is cut off to the south by the Kozhukhovsky intrusive massif of the Martayga complex. In terms of composition, the Cambrian deposits have preliminarily been subdivided by us, from bottom to top, into four major units (formations): the Paromnaya, Smirnovskaya, Chumayskaya, and Karacharovskaya.

The Paromnaya Formation, composed of arkosic sandstones, tuffaceous sandstones, and acidic effusives, with a thickness of more than 150 m, has not been paleontologically characterized.

The Smirnovskaya Formation is substantially conglomeratic; it consists of pyroxene porphyrites, conglomerates with pebbles of red granites, syenites, limestones, and porphyrites, litho-crystalloclastic diagenetically altered tuffs of pyroxene porphyrites, and “lava-conglomerates” based on pyroxene porphyrites with pebbles of intrusive rocks and reworked blocks of limestones with fauna of the “Obruchev” horizon. The thickness of the formation is 1000 m.

The Chumayskaya Formation, with a total thickness of about 1200 m, consists of pyroxene porphyrites, quartz albitophyres, amygdaloidal effusives, and beds of pyroclastic formations. It has not been paleontologically characterized.

The Karacharovskaya Formation, with a total thickness of more than 1500 m, consists of graywackes and polymictic sandstones with two beds of limestones, of which the lower, 50–60 m thick, occurs 300 m above the base of the formation, and the upper, up to 150 m thick, respectively 1200 m above the base of the formation. The limestones of the Karacharovskaya Formation are characterized by archaeocyaths, brachiopods, and algae, and contain gastropods, trilobite fragments, stromatoporoids, and hyoliths. The archaeocyath assemblage is identified as the Kameshkovsko-Sanashtykgol assemblage. A preliminary analysis of the archaeocyath fauna of the Karacharovskaya Formation shows that among the archaeocyaths there are such forms as Batchatocyathus kazakevitsi Vologd., Salairocyathus sp., Asterocyathus salairicus Vologd., Dictiocyathus salairicus Vologd., which are widely distributed in deposits of the Belaya Gorka area near the village of Gorskino, Salair. Along with the listed forms, Archaeolynthus sp., Asterocyathus sp., Protopharetra sp., Ethmophyllum sp., Rhizacyathus sp., Nochoroiocyathus sp., and various Cyclocyathellidae are widespread, likewise widely distributed in the Salair deposits.

On the basis of the archaeocyath assemblage, the limestones of Belaya Gorka may be correlated with the assemblage of the parastratotype of the carbonate section near the village of Sanashtykgol, but they may also be considerably older.

The appearance of an archaeocyath assemblage of a more ancient aspect in the Karacharovskaya Formation, i.e., certainly above the “Obruchev” archaeocyaths and trilobites reworked in the Smirnovskaya Formation, may testify to the recurrence of this “Sanashtykgol” assemblage in the terrigenous facies of Karacharovo. Since the Smirnovskaya Formation contains a reworked faunal assemblage close to the Obruchev assemblage, all the volcanogenic-terrigenous formations of the Chumaysky area lying stratigraphically above it will be younger than the Belokamensk limestones of the Kiya reference section, whose archaeocyath and trilobite assemblage does not contain Obruchev forms [2]. They have no age analogues in the Kiya reference section of the Lower Cambrian and supplement the latter, corresponding to the major break between the Belokamenskaya and Berikulskaya formations of the reference section [2].

The presence of pebbles of granites and syenites in the conglomerates of the Smirnovskaya Formation makes it possible to raise the question of the existence in the Mariinsk taiga of a granitoid intrusion of pre-Middle Cambrian age.

Taking into account the latest materials on the stratigraphy of the ancient strata of the northeastern part of the Mariinsk taiga [2] and adjacent districts of the Sayano-Altai region, the formations of the Chumai district distinguished above, in terms of their faunal characteristics, composition, and stratigraphic position, may preliminarily be correlated as follows.

1. The Karacharovo Formation—with the Ancheshevo Formation of the Salair [3], with the upper, terrigenous part of the “Syi” Formation of the Sarala district [4], with the Bezymyannaya Formation of the Bely Iyus basin [5], with the Cambrian “Azyrtal” Formation of the Azyrtal Range [10], and with the Ulutag Formation of Gornaya Shoriya [9].

2. The Chumai, Smirnovka, and Paromnaya formations are preliminarily correlated with the Pecherkino Formation of the Salair [3], with the lower, volcanogenic part of the “Syi” Formation of the Sarala district [4], and with the Kurlan effusives of Gornaya Shoriya [9].

REFERENCES

1. L. V. Alabin. The Olginsky intrusive massif in the northwest of the Kuznetsk Alatau. Bulletin of the West Siberian and Novosibirsk Geological Administrations, issue 3, 1959.

2. B. D. Vasil’ev; V. D. Kamelina. On the Kiya reference section of the Lower Cambrian. Materials on Mineralogy, Petrography, and Mineral Resources of Western Siberia and Krasnoyarsk Krai. Publishing House of the Tomsk Branch of MOIP, issue 3, 1965 (in press).

3. M. K. Vinkman, A. B. Gintsinger, V. I. Krasnov, A. A. Predtechensky, V. M. Sennikov, A. P. Shcheglov. Stratigraphy of the Precambrian and Paleozoic of the Sayano-Altai folded region. Information Report on Topic 59, SNIIGGiMS, 1963.

4. G. M. Ekhanin. On the stratigraphy of the Sinian-Cambrian formations of the area of the Sarala River. Materials on Geology and Mineral Resources of Krasnoyarsk Krai, issue 2, 1961.

5. G. A. Ivankin, I. I. Koptev, V. E. Nomokonov. On the stratigraphy of the Upper Precambrian and Cambrian of the Kul’byurstog River area. Geology and Geophysics, No. 4, 1964.

6. V. A. Kuznetsov. Geotectonic zoning of the Altai-Sayan folded region. Problems of the Geology of Asia, vol. 1, 1954.

7. D. V. Nikitin. Geological structure and mineral resources of the northwestern part of the Kuznetsk Alatau. Proceedings of TsNIGRI, issue 124, 1940.

8. L. N. Repina, V. V. Khomentovsky, I. T. Zhuravleva, A. Yu. Rozanov. Biostratigraphy of the Lower Cambrian of the Sayano-Altai folded region. Publishing House “Nauka,” 1964.

9. A. G. Sivov. On the stratigraphy of the Precambrian and Cambrian of the Kuznetsk Alatau. Problems of the Geology of Kuzbass, published by TPI, 1965 (in press).

10. V. D. Tomashpolskaya. Stratigraphy and paleontology of the Cambrian of the Batenyov Kryazh and the Azyrtal Range. Abstract of dissertation. Publishing House of TSU, 1964.