ON THE STRATIGRAPHY OF UPPER PRECAMBRIAN AND CAMBRIAN DEPOSITS IN THE AREA OF THE EFREMKINO AND MALAYA SYYA SETTLEMENTS

(Eastern Slope of the Kuznetsk Alatau)

V. E. NOMOKONOV

(Presented by Prof. Dr. K. V. Radugin)

In recent years much attention has been devoted to questions of the stratigraphy of the ancient strata of the Belyi Iyus River basin \[2, 3, 5, 6\]. This interest in the area is due to the fact that it is precisely here that a geosynclinal section of volcanogenic-sedimentary strata of great thickness is exposed—according to our data, about 16–18 km—comprising the Late Precambrian and the Lower and Middle Cambrian, richly characterized by fauna and flora \[1\].

The article offered to the reader presents materials from detailed stratigraphic-paleontological investigations carried out by the author in 1961–1966 as part of a team of scientific workers of the Tomsk Polytechnic Institute (G. A. Ivankin, I. I. Koptev, V. A. Shipitsyn) in the basin of the Belyi Iyus River along the segment of its course between the settlements of Efremkino and Malaya Syya.

Numerous finds of fauna and flora, discovered during detailed geological mapping, and the established relationships of paleontologically characterized strata form the basis of the factual material and make it possible to illuminate in a new way the geological structure and stratigraphy of this interesting area.

The geological structure of the Syya–Efremkino area is shown on the accompanying schematic geological map (Fig. 1).

The principal plicative structures of the area and adjacent territories are the Tyurim and Efremkino anticlines, and the Kulbyurstug, Tarzhul, and Systykkul–Iyus synclines, complicated by numerous disjunctive and plicative structures of second and higher orders.

The stratigraphic section of the area may be represented as follows (from bottom to top): the Poludennaya, Kulbyurstug, and Tarzhul formations of the Late Precambrian (Riphean and Vendian); the Tunguzhul, Kolodzhul, Efremkino, and Bezymyannaya formations of the Lower Cambrian; and the Karasuk and conglomerate formations of the Middle Cambrian.

The Poludennaya Formation is exposed on both sides of the valley of the Belyi Iyus River near the settlement of Malaya Syya and, in the form of a belt of NW strike, extends to the headwaters of Poludennyi Creek and farther into the basins of the Kulbyurstug and Tyurim rivers, where its lower part is exposed in the core of the Tyurim anticline. Within the area described, where the NE limb of this anticline has been preserved (the SW limb is cut off by the Syya fault), only the middle and upper parts of the formation are exposed; they are composed of dark-gray and black bituminous marbles with forms of Sagalinskia, horizons ...

Fig. 1. Schematic geological map of the area of the settlements of Efremkino and Malaya Syya:

1—Quaternary deposits—river-valley alluvium; 2—Lower Devonian—conglomerates, effusives of intermediate and alkaline composition and their tuffs; 3–4—Middle Cambrian: 3—conglomerate unit—boulder-pebble conglomerates, variegated gravelites and sandstones, 4—Karasuk Formation—light-gray, white, whitish-pink, and dark-gray massive limestones; 5–8—Lower Cambrian: 5—unnamed formation—dirty-green and greenish-gray graywacke, tuffogenic (?) and polymictic sandstones, siltstones, marls, lenses of clayey dark-gray limestones; 6—Efremkino Formation—fine-pebble cherry-brown conglomerates, gravelites, cross-bedded sandstones and siltstones, gray, light-gray, white massive limestones, dark-gray and black bedded and massive limestones; 7—Kolodzhul Formation—cherry-gray, pinkish-white clayey limestones, marls, siltstones, cherry-gray and greenish-gray mandelstone diabases; 8—Tunguzhul Formation—light-gray, cream-white, thick-bedded and massive dolomitic limestones, calcareous dolomites; 9–11—Late Precambrian (Riphean and Vendian): 9—Tarzhul Formation—dark-gray, white, yellow-gray, cream-colored dolomites; 10—Kulbyurstug Formation—greenish-gray tuffogenic, graywacke, and polymictic sandstones, gravelites, conglomerates, siltstones, intermediate-basic mandelstone diabases and their tuffs, felsites, albitophyres, lenses and thin interbeds of gray sandy limestones; 11—Poludennaya Formation—diabases, basic-composition tuffs, dark-gray bedded strongly bituminous marbles; 12—Upper Cambrian granitoids (Beloius and Efremkino plutons); 13—plagioporphyry and syenite-porphyry; 14–17—localities of fauna and flora: 14—trilobites, 15—archaeocyaths, 16—stromatolites, catagraphs, oncolites, algae; 17—elements of bedding attitude; 18—stratigraphic and intrusive boundaries; 19—disjunctives.

tuffaceous sandstones, tuffaceous shales, and diabase porphyrites. The rocks of the suite are folded into tight folds of NE strike and are cut by the Tyurim intrusion of gabbro-diabases. In the deposits of the suite along the Tyurim and Kulbyurstug rivers and in the area of the Kommunar mine, the following were collected and identified by V. A. Shipitsyn: Newlandia sp., Saralinskia sp., Archaeospongia sp., Osagia ovosimilae Vol.

The above complex of organic remains quite reliably proves the Upper Proterozoic (Middle Riphean) age of the deposits of the Poludennaya Suite.

Stratigraphic analogues of the Poludennaya Suite in other areas of the Kuznetsk Alatau, in our opinion, are the Bidzha Suite of the Batenyov Range [6], the Glavstan Suite of Sarala, and the Unushkol Formation of Gornaya Shoriya.

The Kulbyurstug Suite was distinguished by us as an independent, distinctive volcanogenic-clastic unit, lying unconformably on the deposits of the Poludennaya Suite and everywhere overlain by carbonate rocks of the Tarzhul Suite [1].

Within the area described, deposits of the Kulbyurstug Suite are developed in two sectors: on the watershed of Smorodinny Brook and the Kulbyurstug River, where they make up the Kulbyurstug syncline, and on the left side of the Malaya Syya River, where they compose the NW limb of the Systykzhulo-Iyus syncline (Fig. 1). At the base of the suite in the basin of the Kulbyurstug River lie greenstone porphyrites and conglomerates, which higher in the section are replaced by gravelites, various-grained graywackes, tuffites, tuffaceous sandstones, and tuffaceous shales with thin interbeds of sandy limestones. The thickness of this part of the suite in the stratotype section is 800–850 m. The middle part of the suite, whose thickness does not exceed 600–800 m, is characterized by intermediate-basic effusives (diabases and diabase porphyrites) with a subordinate amount of tuffs of the same composition and lenses of gray dolomites. The upper part is composed of alkaline and acidic (?) effusives—albitophyres, orthophyres, and felsites—with a thickness from 50–80 m (Kulbyurstug River) to 100–120 m (Tyurim River). The latter are completely absent on the left side of the Malaya Syya River. The total thickness of the suite in the stratotype section is 1800–1900 m.

The deposits of the suite are poor in paleontological remains. In interbeds of dark-gray marbles on the watershed of the Malaya Syya River and Systyk-Zhula Brook (point Sh-053), we found oncolites Osagia ovosimilae Vol., indicating a Late Precambrian age of the suite.

It should be noted that deposits similar to the Kulbyurstug Suite are also traceable in other areas of the Kuznetsk Alatau. On the Batenyov Range they are known as effusives of the Loshchenkov Suite and effusives of Mount Romanovskaya near the village of Katyushkino [4].

The Tarzhul Suite lies, without visible structural unconformity, on the volcanogenic-clastic rocks of the Kulbyurstug Suite. There is no single section of the suite in the area, since it has been preserved only in separate tectonic blocks (Fig. 1).

The lower part of the suite is best exposed on the left side of the Kulbyurstug River, where it is composed of the central part of the Kulbyurstug syncline, and on the watershed of the Malaya Syya River and Systyk-Zhula Brook in the western limb of the Systykzhulo-Iyus syncline. At the base of the suite lie dark-gray thin-bedded dolomites about 50 m thick. Higher in the section they are replaced by gray, light-gray, and white unevenly bedded silicified dolomites. Their visible thickness in the Kulbyurstug syncline is 500–550 m, and on the Systyk-Zhula and Malaya Syya watershed, 1200–1300 m.

The higher part of the section of the Tarzhul Formation is well exposed on the left and right sides of the Bely Iyus River south and southeast of the settlement of Malaya Syya. Here the Tarzhul Formation is composed of yellowish-gray, gray, and light-gray distinctly bedded dolomites, which make up the southeastern limb of the Tarzhul syncline, downthrown along the Syya fault. The visible thickness of the rocks of the formation in this block is not less than 2.5–3 km. The section of the formation is built up farther to the northeast, in the headwaters of the Tyurim stream, outside the area described. The total thickness of the Tarzhul Formation is estimated approximately at about 3.5–4.5 km.

The formation is fairly well characterized by paleontological remains. Stromatolite beds are characteristic of the lower part of the formation (level—500–1000 m). In various tectonic blocks at this level, the following were collected and identified by V. A. Shipitsyn: Irregularia Koroljuk, Stratifera Koroljuk, Conophyton Maslov (pts. 12300, 16, sh-035), Vesicularites flexuosus Reitl (pts. 12300, 16). In the upper part of the formation, in the basin of the Tyurim stream, poorly preserved stromatolites and catagraphia were also found.

On the basis of the cited flora assemblage, we consider it possible to assign the Tarzhul Formation to the uppermost Late Precambrian (Upper Riphean and Vendian) and to regard it as an analogue of the Sosnov Formation of the Batenev Range [5]. We note that earlier the deposits of the Tarzhul Formation were erroneously included by V. M. Yaroshevich [6] in the Middle Cambrian Sytykzhul Series.

The Tunguzhul Formation is exposed in rocky outcrops on the left and right sides of the valley of the Bely Iyus River north of the settlement of Malaya Syya and, as a narrow arcuate belt, can be traced into the valley of the Smorodinny stream. In addition, carbonate rocks of the Tunguzhul Formation are exposed in narrow tectonic blocks on both sides of the valley of the Bely Iyus River above the bridge and on the left side of the mouth part of the valley of the Kulbyurstug stream.

The Tunguzhul Formation lies without visible structural unconformity (conformably) on rocks of the Tarzhul Formation. However, in individual areas (in the mouth part of the Kulbyurstug valley, on the western slope of Mount Koshkulak, where its stratotype is described), sedimentary breccias and conglomerate-breccias are observed at the base of the formation. The formation is composed of light-gray, gray, and siliceous-white algal limestones, dolomitic limestones, and fragmental dolomites. The total thickness of the rocks of the formation in the area described does not exceed the first hundreds of meters (about 500 m). Throughout the entire belt of outcrop of the formation, oncolites, catagraphia, algae, and, at two points (pts. 11 and 4—63), rare trilobites were found in many places in the roof of the formation. V. A. Shipitsyn identified from here: Osagia ex. gr. bothrydioformis Krasn., Vermiculites angularis Reitl., V. sp., Botominella lineata Reitl., B. densata sp., Vologdinelleae sp., (Arnganella sp.), Paleonites jacuticus Maslow, Glebosites sp., Archaeasphera cambrica Reitl., Girvanella sibirica Masl. From points 11 and 4—63, I. I. Koptev identified the trilobites Bulaiaspis sp. and Bagradia sp.

On the basis of the above assemblage of paleontological remains, the Lower Cambrian age of the formation is determined with sufficient confidence. This gives us grounds to begin the Cambrian section of the given area from the base of the Tunguzhul Formation and to correlate it with the Bograd Formation of the Batenev Range [4].

The Kolodzhul Formation. Deposits assigned by us to the Kolodzhul Formation lie without visible structural unconformity (conformably) on rocks of the Tunguzhul Formation and at the level of the present-day denudation surface have been preserved only in two areas: on the right side

of the Belyi Iyus River above the bridge and on both sides of the valley of Smorodinnyi Brook below the limestone quarry.

On the right bank of the Belyi Iyus, in the upper part of the rocky outcrops of the limestones of the Tunguzhul Formation, a synclinal fold has been preserved, composed of variegated volcanogenic-terrigenous-carbonate rocks with a total thickness of about 80–100 m. On the basis of lithological similarity with the basal member of the overlying Efremkino Formation, E. V. Shirokova and L. N. Repina [5] erroneously assign these deposits to the Syya (our Efremkino) Formation.

The section of the deposits of the Kolodzhul Formation in the Iyus syncline may be represented as follows (from bottom to top):

1. Cherry-colored sandstones, gravelites, dark-cherry and green siltstones, marls, sandy limestones. Thickness 26–28 m.

2. Gray-green and dark-cherry (in the upper part) amygdaloidal diabases and diabase porphyrites. Thickness 20–30 m.

3. Pinkish-white and cherry-colored sandy and clayey limestones with interbeds of dark-cherry cross-bedded sandstones, siltstones, fine-pebble conglomerates, and gravelites. Thickness 35–40 m.

In member 3, in a one-and-a-half-meter interbed of dark-cherry clayey limestones (locality 29, Fig. 1), trilobites were collected by us following E. V. Shirokova. I. I. Koptev identified from here: Koshkulaspis procera gen. et sp. nov., Alanisia efremkinaensis Rep. (MS), A. plana Rep. (MS), Kolbinella cf. prima Rep., Aldonellus cf. lepidus gen. et sp. nov., Lenaspis sp. From E. V. Shirokova’s collections from this same locality, L. N. Repina [5] additionally identified: Strenueeva rara Rep., Hamatolenus geosiclinalicus Rep., Lenaspis divergens Rep., Paratungusella sp.

On the right bank of Smorodinnyi Brook, near the quarry, the variegated member described above is also exposed, overlain by basal conglomerates of the Efremkino Formation. Its visible thickness here does not exceed 50–60 m. In the white-pink clayey limestones of this member, lying above the amygdalophyres, 35 m from the base of the formation, trilobites Koshkulaspis sp., Bulaiaspis sp. were found (identified by I. I. Koptev).

On the basis of the above-mentioned assemblage of organic remains, lithological features, and stratigraphic position in the section, the described variegated member is quite reliably correlated with the Kolodzhul Formation of the Koshkulak Mountain area, having in common with it 6 species of trilobites. The very small thickness of the formation in the section described is explained by its distinctive facies character (nearshore facies) and by subsequent erosion before deposition of the overlying Efremkino Formation.

The Efremkino Formation is exposed on the watershed of Poludennyi and Smorodinnyi brooks and, as a belt of submeridional strike, is traced to the head of the Senokosnyi log, which enters from the left into the valley of the Kulbyurstug River. The Efremkino Range is also composed of carbonate rocks of the Efremkino Formation.

The best section of the formation, accepted as the stratotype, is its section along the right bank of Smorodinnyi Brook above the quarry. Here the following section of the formation is observed (from bottom to top):

1. Basal fine-pebble conglomerates with pebbles of diabases, diabase porphyrites, orthophyres, felsite-porphyries, white-pink and dark-gray limestones. Thickness 8 m.

2. Variegated (predominantly red-colored) polymictic sandstones of varying grain size, siltstones, gravelites. Thickness 140 m.

At 80 meters from the base of the conglomerates, among the terrigenous rocks, a one-and-a-half-meter bed of greenish-gray clayey limestones is traced, in which brachiopods, hyoliths, and rare tri-

lobites. I. I. Koptev determined from here (loc. IZ-0) Chondragraulaspis artus gen. et sp. nov.

1. Light-gray, white, thick-bedded and massive algal limestones with trilobites and archaeocyaths, lying conformably on the terrigenous member. Thickness 55–60 m.

At 160–165 m from the base of the suite (loc. IZ-1), in white massive limestones, trilobites were collected: Chondragraulos sp., Bathyuriscellus cf. robustus Lerm., Parapoliella cf. obrutchevi N. Tchern., Katunia? sp. (Onchocephalina? sp.), Onchocephalina cf. arguta Rep., Jangudina cf. quadrata Koptev (MS), Solontzella lata sp. nov., S. sp., Prolaminurus cf. bateniensis Tomashp., Bergeroniaspis? sp., Namanoia cf. incerta N. Tchern. (determinations by I. I. Koptev), archaeocyaths: Ethmophyllum amsassense Krasn., Retecyathus sp., R. altaicus Krasn., R. operosus Zhur., Archaeocyathus regularis Vol., A. cf. erbiensis Zhur. (determinations by V. D. Kamelina), algae: Epiphyton reniforme Korde, Renalcis sp., Girvanella cf. conferta Champ., Palaeachlya sp., Cavifera concina Reitl. (determinations by V. A. Shinitsyn).

1. Dark-gray and black, strongly bituminous, platy limestones, gradually passing into gray and dark-gray massive limestones. Thickness 60–70 m. In the black platy limestones, at 230 m from the base of the suite (loc. IZ-2), trilobites, hyolithids, and brachiopods were collected. I. I. Koptev determined from here: Chondragraulos minussensis Lerm., Katunia? sp. (Onchocephalina? sp.), Solontzella cf. pallida Rep., Namanoia? sp., Kutorgina sp., and Nisusia sp.

Higher in the section there are exposed dirty-gray and greenish-gray graywacke sandstones, siltstones, and marls of the unnamed suite, lying unconformably on the limestones of the fourth member of the Efremkino suite. The visible thickness of the Efremkino suite in the stratotype is 350 m.

The black platy limestones of the fourth member of the stratotypic section can be traced southward to the head of Poludenny Brook, where, as early as 1956, V. V. Khomentovsky found trilobites in them (loc. 19, fig. 1): Kolbiniella prima Rep., Kolbiniella sp., Jnouyina sp.

In 1958, during repeated collecting, D. I. Musatov [3] additionally collected from here Bathyuriscellus sp., Cobboldia sp., Solenopleurella sp., Acrotreta sp., and Obolus sp. In 1962 we found here as well Olgaspis Korob., Jangudina sp., J. quadrata Koptev (MS), Namanoia cf. incerta N. Tcher. (determinations by I. I. Koptev).

Higher beds of the Efremkino suite are exposed north of the described stratotypic section, on the right side of Senokosny Log, at the elevation of 886.9 m. Here, in dark-gray massive limestones, trilobites were collected: Onchocephalina sp. (loc. 32a), Chondargraulos minussensis Lerm., Kooteniella slatkowskii (Schn.), Gaphuraspis? sp. (Solenopleura? sp.), Chondranomocare sp. (loc. III—507)—determinations by I. I. Koptev.

A somewhat different section of the Efremkino suite can be observed west of the one described, on the right side of the valley of Smorodinny Brook, near the pig farm. Here, in the overturned SW limb of the Efremkino anticline, immediately beyond a disjunctive fault (?), along which the sandstones of the unnamed suite and the dark-gray shaly limestones of the Efremkino suite are in contact, I. I. Koptev found archaeocyaths in the dark-gray bituminous limestones (loc. 7a): Erbocyathus sp., Tercyathus sp., Vologdinosyathus sp., Archaeocyathus regularis Krasn., Annulofungia sp., Syringocnema eleganta Vol. (determinations by V. D. Kamelina).

Higher up the slope (to the NE of loc. 7a), the dark-gray limestones are gradually replaced by light-gray and gray massive ones. At 160 m from

In bed 7a, and beneath them (bed 9), indeterminate trilobites were found; at 300 m—archaeocyaths (bed 7b): Erbocyathus heterovallum Vol., Tegerocyathus sp., Archaeocyathus sp., Uralocyathus sp., Annulofungia taylori Krasn., Ajacicyathus tomicus Vol., Tercyathus sp., Sajanocyathus sp., Retecyathus sp., Protopharetra sp., Tegerocyathus erbiensis Krasn. (identified by V. D. Kamelina); at 750 m, immediately below the base of the overlying unnamed suite (bed N—5), brachiopods, rare archaeocyaths, and trilobites: Namanoia cf. incerta N. Tchern., Kooteniella slatkowskii (Schm.), Chondragraulos minussensis Lerm., Kutorgina sp. (identified by I. I. Koptev). The visible thickness of the Efremkino Suite in this section is 750–800 m.

From the description of the sections given above it is clearly evident that the Efremkino Suite is distinctly separated from the underlying Tunguzhul and Kolodzhul suites both by paleontological remains characteristic of the Solontsy and Obruch horizons and by its unconformable occurrence upon them (Fig. 1). In contrast to our predecessors [2, 5], who retained the old name for this unit—the Syya Suite—we propose a new name, Efremkino, since the concept of the Syya Suite has long since lost its meaning [1].

Unnamed suite. Its unconformable occurrence upon the Efremkino Suite is clearly visible on the appended geological map (Fig. 1). The suite is composed of a monotonous sequence of dirty-gray and greenish-gray graywacke and tuffaceous (?) sandstones, siltstones, and marls, with thin interbeds and lenses of dark-gray limestones. Its visible thickness in the section along Smorodinnoye Creek is about 700 m. The suite is poor in paleontological remains. In the area of the Efremkino Range, indeterminate remains of trilobites were found (bed 35), and near the synform (50 m west of bed 7a), in a half-meter interbed of limestone, brachiopods Kutorgina and trilobites: Olenoides, Pagetia sp. (identified by I. I. Koptev) (bed 3–66)*.

Sequences of sandy-shaly rocks close in composition and stratigraphic position to the unnamed suite are developed within the Bateny Ridge and are known in the literature as the Son and Tolcheya suites [4].

Karasuk Suite crops out in a narrow wedge-shaped graben north of the settlement of Malaya Syya. The suite has no stratigraphic contact with the underlying or overlying units. It is composed of white, dark-gray, siliceous, brownish massive limestones with a rich trilobite fauna of the Suyaryk horizon of the lower part of the Middle Cambrian (localities 17, Sh-050, N-6, and others). On the presence of such forms as Olenoides, Amgaspis, and Gaphuraspis, the unit described is well correlated with the Malokoshkulak Suite of the area of Mount Koshkulak [1], and with the upper part of the Yulian Suite of the Bateny Ridge [4].

Conglomerate unit crops out on the right side of the valley of Poludenny Creek over a small area (see Fig. 1) and has a thickness of about 400 m. It lies transgressively on the underlying units (Tunguzhul, Kolodzhul, Efremkino) and is represented by boulder and coarse-pebble conglomerates, which eastward are gradually replaced by variegated gravelites, sandstones, and siltstones with interbeds of clayey limestones. The composition of the conglomerates is rather varied. The boulders and pebbles are represented by diabases, plagioporphyries, and various limestones. From limestone pebbles, well-preserved trilobites were collected (bed 41): Erbia granulosa Lerm., Kooteniella sp., Bathyuriscellus sp., Binodaspis sp., Solontzella modesta Rep., Onchocephalina plana Rep., Erbia sp. (identified by I. I. Koptev and L. N. Repina).

*) In 1967, V. A. Shipitsin found Middle Cambrian trilobites in this same unit along Izvestkovy Creek near the hut: Olenoides, Peronopsis, Neopagetina.

The stratigraphic position of the conglomerate unit has not been precisely established. It is quite possible that the unit described is the basal member of the unnamed suite, as is suggested by the seemingly gradual transition upward into the sandy–shaly rocks of the unnamed suite. At the same time, the extremely limited area of conglomerate outcrops seems strange. The latter gives us grounds for the time being to distinguish this unit as independent (possibly post-Karasuk).

REFERENCES

1. G. A. Ivankin, I. I. Koptev, V. E. Nomokonov, V. A. Shipitsyn. On the stratigraphy of ancient sequences of the eastern slope of the Kuznetsk Alatau. Materials on the Geology of Western Siberia, Tomsk State University Publishing House, issue 3, 1966.

2. B. N. Krasil’nikov. On the subdivision of Lower and Middle Cambrian deposits of the eastern slope of the Kuznetsk Alatau. Geologiya i geofizika, No. 1, 1962.

3. D. I. Musatov. Stratigraphy of Cambrian deposits of the eastern slope of the Kuznetsk Alatau. Geologiya i geofizika, No. 2, 1961.

4. V. D. Tomashpol’skaya. Stratigraphy and paleontology of the Cambrian of the Batenyov Range and the Azyr-Tal Ridge. Author’s abstract of dissertation, Tomsk, 1964.

5. E. V. Shirokova, L. N. Repina. The Torim–Efremkino reference section of the Cambrian in the Kuznetsk Alatau. New Data on the Geology of the South of Krasnoyarsk Krai, Krasnoyarsk Book Publishing House, 1964.

6. V. M. Yaroshevich. Stratigraphy of Sinian and Cambrian deposits of the Batenyov Range, the Azyr-Tal Ridge, and the basin of the Bely Iyus River. Publishing House of the Siberian Branch of the USSR Academy of Sciences, 1962.