Some Problems of the Tectonics of the Kuznetsk Coal Basin

K. V. Radugin.

1. On the Orian and Sukhaya Phase of Folding in the Kuznetsk Coal Basin (Based on Observations near the Town of Orlinaya)

The district of the Guryevsk plant is, for the geology of Kuzbass, a classical district. Not for nothing was it one of the few places selected in Siberia for the excursion of the International Geological Congress in 1937.

This district still continues to provide us, one after another, with very important facts for tectonics and stratigraphy. Recently one of them was briefly discussed by me. It concerns the question of the exact age of one of the phases of the Salair cycle of tectogenesis (4). Here I wish to share the emerging conclusions concerning younger movements.

First of all, let us note the folding movements that preceded and followed the formation of the ostracod limestones of the town of Orlinaya, hereafter called the ostracod formation.

In tracing the boundaries of this formation and of the Sukhaya formation $S_2$ (6) underlying it, the following contours were obtained (Fig. 1).

As we see, the thick ostracod limestones sharply decrease across the entire width of the belt if they are traced from the syncline toward the closure of the Orlinogorsk anticline. How is this fact to be explained? First of all, let us suppose that this is the result of a gentler dip of their beds on the limb of the fold as compared with the dip in the saddle of the anticline. True, such a relationship is unnatural and is not encountered in nature, at least in the case of conservative folding, if we exclude cases of flexure-like bends of the limbs of folds, as well as drag folds at disjunctives, where the primary dip may increase up to $90^\circ$. But we shall nevertheless take this improbable case into account as well and see what the actual elements of occurrence of the formation are.

In this respect the following data are available. The Sukhaya formation, at the latitude of the limb under consideration by us, has an angle of dip equal to $60$—$70^\circ$; on the other hand, in the overlying thickness of Middle Devonian limestones we observe an angle of dip of $50$—$60^\circ$ and only rarely $45^\circ$. According to the law on the angles of dip in the limbs

Fig. 1. Detail of the map of the area of Mt. Orlinaya (near the Guryevsk plant). A microfault is visible, formed before this corrosion.

Fig. 2. A phenocryst of labradorite, corroded by the groundmass (dots) of corrosion.

Fig. 3. Section along the right bank of the Tom River at the mouth of the Taragan stream, with discordant superposition of the Jurassic (1) upon the Permian (2).

Fig. 4. Relict tectonostructures, expressed in the form of a sandstone fragment of the productive series of Kuzbass (from the Jurassic conglomerate of the Tom near the Taragan stream).

Fig. 5. The meandering valley of the Mrassa River, incised into granite (crosses) and marbles.

of concordant or consequent folds, the dip angles of the intervening unit must also be intermediate; only in the extreme case can they be equal to the dip angles of the overlying formation. The anticline of the town of Orlinaya is a typical representative of inherited folding. Consequently, the dip angle of the ostracod limestones is no less than 50° and no more than 70°, with some measurements giving 65°; hence their thickness in the section being analyzed can vary only within the limits of 500–600 m (with the width of the belt of ostracod limestones being 600–650 m).

Something quite different is observed in the closure of the anticline of the town of Orlinaya. Here it should be noted that at the base of the ostracod limestones there is a characteristic horizon of calcareous-clayey rocks with Syringopora sp. and others and with characteristic brachiopods. Upon them lie limestones of reef facies with abundant corals, in particular with Favositiidae, Amplexus?; with species of the genus Pycnostylus or Cyathopaedium Schlut. with characteristic intrathecal budding; especially characteristic of this horizon is a species of the genus Gephuropora, which until recent years had been known only from Australia¹. Owing to the presence of the latter species, easily recognizable in the field, the basal horizon of the ostracod limestones is easily traceable as far as the closure of the Orlinogorsk anticline. And here it turns out that the unit of dark ostracod limestones lying above it is very thin: measuring only tens of meters, it is replaced northward by light-colored limestones not characteristic of the ostracod unit.

We explain all these facts as follows. At the time of deposition of the gephuropora horizon our area represented a sea floor with a depth of from 0 to 40 m, and—let us emphasize—this depth was also observed within the closure of the Orlinogorsk anticline. The latter therefore did not then constitute a noticeable elevation on the sea floor.

Subsequently the reef facies was replaced by the facies of ostracod limestones. Since corals are also encountered here, at times in large colonies, as well as gastropods and other fossils, we assign this facies to that variety which, according to Prof. D. V. Nalivkin (2, 132–3), is formed at a depth of 60–80 m. It is quite possible that at times the depth of the sea was less, since, apparently, here and there within the ostracod limestones there are also coral banks or small reefs.

Since the thickness of the ostracod limestones is much greater even than 80 m, reaching near the closure of the Karachinskaya syncline 500–600 m (and according to the data of V. I. Yavorsky and others this figure for the Kuzbass is estimated at about 1 km), we have before us a typical case of slow subsidence of the earth’s crust, accompanied, perhaps, by small, sharper movements. Sum-

the total depth of the downwarp is determined, at a minimum, by the maximum thickness of the ostracod limestones. In reality it was greater, since after their formation they were subjected to erosion.

This erosion must necessarily be acknowledged if one takes into account the complete uniformity of the facies of the ostracod limestones of the Orlinaia River. We cannot allow that, at a distance of 1 km or less, under the same conditions, almost 0.5 km less of ostracod limestones accumulated. Explaining the decrease in their thickness precisely in this way, we note that erosion proceeded to its maximum extent in the crest of the Orlinogorsk anticline, and that the ostracod limestones reach their maximum thickness in the neighboring Karachkinsk syncline. All this is explained by a phase of folding that took place after their formation, but before the subsequent denudation, before the transgression of the Lower Devonian sea and the deposition of the Krekovo limestones.

The question is resolved no less definitely also with respect to the phase of folding that occurred before the deposition of the ostracod limestones. In the footwall of the latter lie Givetian beds and basal clayey-marly deposits. And these basal horizons in the crest of the anticline of the Orlinaia River directly overlap the limestones of the Lower Silurian (the Beberov Formation of Acad. M. A. Usov), whereas on the limb of the anticline the Sukhaia Formation receives considerable development.

Thus, the conclusions recently published by Acad. M. A. Usov and concerning the Sukhaia and ostracod formations and the corresponding phases of tectogenesis are confirmed by new data obtained in recent years.

2. Traces of Upper Devonian volcanism in the Kuznetsk Basin.

During the work of the cabinet geologists, the conviction had taken shape that Upper Devonian effusives were widely developed in the Kuznetsk-Altai region. It found expression even in more recent works, but then Acad. M. A. Usov and Prof. A. M. Kuzmin, as a result of their investigations in the basins of the Lebed and Tom rivers (1; 6; 7), decisively refuted the old ideas, showing that the so-called Upper Devonian effusives are more ancient and that the Upper Devonian, faunistically proven, rests unconformably upon them. At the same time these investigators concluded that effusives are completely absent from the Upper Devonian section of the Kuznetsk Basin.

Such a conclusion fully corresponded to the state of our knowledge ten years ago. But now it again has to be modified and it must be recognized that effusives do occur in \(D_3\). It might seem that in this way we are returning to the old views of the cabinet geologists. In fact this is not so; in fact, the recent progress of our knowledge—the establishment of the unconformable superposition of Upper-

…of the Lower Devonian onto the main mass of Devonian effusives—remains unshaken, but our knowledge is being refined: we apparently must also recognize the presence of Upper Devonian effusives.

What, then, are the facts that form the basis for such a conclusion? They were obtained in part as early as 1931 by the geologist A. G. Sivov in his investigations of the Korai planchet of Mountain Shoria (5). According to these data, within the lilac-red shales of the Upper Devonian the following igneous rocks were discovered (Table A).

Table A.

Of these three points, specimen No. 3 is of particular interest, since nearby, along the Ulugol key, Eospermatopteris textilis Daws. was found in the sandstones (as determined by Prof. V. A. Khakhlov), which in North America characterizes \(D_3^3\). According to A. G. Sivov’s observations, these sandstones are interbedded with the basal conglomerates \(D_3\), cut by the dike mentioned in Table A.

Despite these rather convincing facts, under the influence of the prevailing view of the complete absence of volcanic activity in \(D_3\), A. G. Sivov showed on his report map the effusives of points Nos. 1 and 3 as horst wedges composed of Telbes effusives and bounded by \(D_3\) disjunctives.

In the summer of 1938 I had occasion to see one of the outcrops of Table A, namely outcrop No. 1. Here, chiefly in the form of large blocks in the channel, but here and there also in bedrock exposures, porphyrites are exposed, whose platy jointing (L) runs almost parallel to the beds of the variegated Upper Devonian sequence lying in their hanging wall. Elongated phenocrysts of plagioclase are likewise arranged in the rock. Since the porphyrite contains rather large and frequent rounded amygdules (of calcite and chlorite), we may assign it only to a cover, or sill-like, nearly surface facies.

This effusive cannot be regarded as Telbessian by assuming an anticline at this place, since to the east of the porphyrite described the beds of the Upper Devonian variegated sequence dip gently westward, toward the porphyrite, and not eastward.

Finally, let us note that the porphyrite contains inclusions of variegated shales captured by it during eruption, i.e., rocks quite uncharacteristic of the Telbessian formation exposed somewhat farther east. In addition, within the porphyrite itself there are fractures filled with sandy-clayey variegated material. They testify to physical weathering of the effusive before it was buried by the variegated sequence of the Upper Devonian. All this definitively convinces us that the effusives described do not at all constitute the core of the Telbessian formation, but are inseparably connected with the variegated Upper Devonian sequence, representing one of its horizons.

Thus it is necessary to draw the conclusion that geotectonic development in the Upper Devonian epoch in the Kuznetsk Basin did not occur without the participation of volcanism. True, this conclusion rests on the responsibility of Prof. V. A. Khakhlov, to whom we owe the determination of the age of the variegated sequence of the Poguzak River. But the geological data do not contradict this. First of all, let us note that the Upper Devonian of the Koraika planchet unconformably overlaps the variegated sequence, which in turn, through conglomerates, lies on the Telbessian formation and belongs either to the Antropovka or to the Abramovka formation. On the other hand, this same Devonian at its base contains fragments of quartz syenites, which metamorphose not only the Telbessian effusives, but also the Telbessian adamellites of the Tom and Bel-Su rivers. Since these syenites formed after the Abramovka formation, our Devonian, obviously, is younger than it.

The conclusion obtained here can be checked in the section along the Use River, where, according to I. Tolmachev’s data, there is a sill of porphyrite in such a Devonian horizon, which lies above limestones with marine fauna of the Upper Devonian.

Since the D₃ effusives of Solonechny Spring acquire independent significance—the significance of a special volcanic phase—they should be examined more attentively.

Externally, these are reddish or brownish massive rocks,

in the aphanitic groundmass of which large (up to 1–2 cm in diameter) round or elliptical amygdules of calcite and black chlorite are visible, as well as phenocrysts of faintly greenish, sharply zoned feldspar with polysynthetic striation. In one inclusion one can recognize an accidental fragment of vein quartz with hematite.

Owing to the large number of inclusions of elongated large plagioclase crystals, the rock very much resembles a labradorite porphyrite. But under the microscope the picture proves to be more complex. First of all, the plagioclase phenocrysts turn out in some cases to be clearly foreign inclusions of alien material, captured during the outpouring of the magma. Here is one of them in its most vivid manifestation (Fig. 2).

Here we see a grain of zoned labradorite, corroded by the magma, with metasomatic inclusions of dirty-greenish (in ordinary light) chlorite. Usually such grains are considered phenocrysts crystallized at depth in the same magma in which they are now found. But in the present case we have a typical case of relict tectonostructures of xenoliths of magmatic rocks and of their components (3). In fact, our plagioclase crystal was first fractured; transverse, relative to the polysynthetic twins, micro-displacements and shear bends appeared in it, and only after this did it enter, as a fragment, the magma of the dike rock described, where it was subjected to melting. That the displacements occurred before melting is clearly seen from the fact that they do not pass into the groundmass, and precisely that part which would protrude in the absence of melting protrudes only slightly into the groundmass (Fig. 2).

Thus, to a considerable extent, and perhaps even entirely, the “phenocrysts” of the rock described are in essence foreign microxenoliths. If it were poorer in anorthite than labradorite, we should expect a secondary increase of the plagioclase of the groundmass at the expense of assimilation of labradorite fragments.

What, then, is the groundmass represented by? It is heavily packed with a dense sprinkling of hematite and specular iron ore (?), which gives the rock its characteristic reddish-brown coloration. Besides ore minerals, chlorite is also visible in the groundmass in the form of fine-scaly aggregates; these aggregates have irregular outlines, as if they were impregnated, and evidently represent the result of metasomatism of the groundmass, in particular of its plagioclase, but by no means are pseudomorphs after dark-colored minerals. No traces of the latter have been found at all.

If one excludes the chlorite and ore minerals mentioned above, the remaining mass consists exclusively of acid plagioclase, the laths of which are arranged in all possible directions and are 0.1–0.3 mm long.

3. On the question of the relation of the Lower Carboniferous to the Upper Devonian.

A gradual transition from \(D_3\) to \(C_1\) and, consequently, their conformable occurrence in the southeast of Kuzbass was until recently the usual conception, and the section along the Tom River was even cited as an example of such a gradual transition (8, 67, 69, and 115).

The recent works of A. A. Zenkova, O. K. Poletaeva, and V. A. Kuznetsov have introduced corrections here concerning the NE part of the basin. We wish to share new data that concern the section along the Tom River and the Bel-Su, the classic area of the “gradual” transition from \(C_1\) to \(D_3\). These observations contradict the former conceptions. They indicate a discordance between \(C_1\) and \(D_3\), since in the lower parts of the Lower Carboniferous there are horizons with pebbles of Upper Devonian dolomitized limestone; this circumstance proves erosion of the Upper Devonian deposits before the deposition of the lower horizons of the Lower Carboniferous. The occurrence of the latter at different horizons points to the same thing.

The same conclusion, not only about a break in deposition but also about erosion, is obtained from observations near the village of Kuzedeevo, where P. I. Butov and V. I. Yavorsky noted fragments of shales (8, 61) in the basal horizons of the Carboniferous limestones. Let us also note that on the divide between the Tom and Mrassa, between the rivers M. Maizas and Kumzas, the Lower Carboniferous lies directly on the Telbes Formation, as A. G. Sivov depicted (5, map), and a little farther north on the Upper Devonian with an angular azimuthal unconformity. True, there A. G. Sivov showed a disjunctive boundary, but in all good sections (along the rivers Usa, Bel-Su, Tom, Maizas, and Mrassa) a normal superposition of \(C_1\) on \(D_3\) is observed, with very calm and gentle bedding. This fact, if it is confirmed by accurate mapping, will already testify also to a weak manifestation of folding between the Lower Carboniferous and the Upper Devonian.

In connection with the absence of any significant conglomerates at the base of the Lower Carboniferous, it will be very difficult to establish those intrusive rocks that were associated with the phase of plicative dislocations established here between \(C_1\) and \(D_3\). In this respect, more hope is offered by the N and SE margins of Kuzbass.

4. On tectogenesis between the Permian and the Jurassic.

Pre-Jurassic folding is well established in the section along the Tom River, as has already been noted by a number of investigators of Kuzbass; moreover, V. I. Yavorsky (8), to be sure not altogether confidently, ascribed great intensity to the post-Jurassic folding.

Here, above the mouth of the Mrassa River and below the mouth of the Usa River, at the mouth of the Tarbagan River, we observe a distinct angular unconformity between the footwall of the Lower Jurassic and the beds of the Upper Paleo-

(Fig. 3). In the schematic drawing given here, this clear unconformity is expressed as it is seen directly from a boat or from the left bank of the Tom. In the eastern limb of the Tarbagan syncline, somewhat above the Tarbagan River, the angular unconformity measures approximately \(20^\circ\) with dips in the same direction, and in the western limb, \(40^\circ\) with dips in different directions. However, as is usually the case with accordant folding, in the western limb of the anticline shown (Fig. 3) there is probably no noticeable angular unconformity.

The pre-Jurassic folding thus established is also confirmed by the weaker dislocation of the Jurassic, as is evident in the available sections of the Kuznetsk coal basin, and by the discordant bedding of the Jurassic on its various suites. In harmony with this fact are the lesser diagenesis and greater friability of the Jurassic deposits as compared with the Upper Paleozoic ones. They are less affected by regularly oriented jointing connected with folding processes. Finally, in the basal Jurassic conglomerate the sandstones of the productive series of the Kuznetsk basin already possess distinct relict tectonostructures, expressed in the form of fragments (Fig. 4), as remnants of the flat surfaces of an oblique parallelepiped.

Thus the observations cited above show, first, that the dip angles of the Paleozoic sequence before the Jurassic dislocation reached \(40^\circ\) in the described area, whereas the Jurassic deposits here dip no more steeply than \(30^\circ\).

Other conditions being equal (since the observations were made in one and the same vertical section), it must be recognized that the pre-Jurassic folding was of greater intensity than the Jurassic-Cimmerian dislocations. This conclusion, supported by the observations given above on relict tectonostructures, should of course not be extrapolated to other parts of Kuzbass, especially to the west, where the Cimmerian movements may have attained greater intensity than the Upper Paleozoic ones.

5. Traces of Tertiary Dislocations along the Margins of Kuzbass

During work in 1928–1929 along the northern margin of the Kuznetsk basin, the author, while studying the section along the Alchedat River in the Anzherka region, encountered clear traces of weak tectonic movements that affected the Tertiary deposits.

Along this river we have a clearly expressed imbricate structure, since the Middle Devonian of the village of Lebedyanskoye is cut here by a number of thrusts into numerous slices. In one of these slices overturned bedding of coral limestones is observed, established from the arrangement of branching corals and loaf-shaped colonies of Favosites.

Before the formation of a continuous cover of Tertiary deposits,

that closed the Paleozoic; weathering pockets formed on its surface in the limestones; owing to the selectivity of this process they especially often coincided with the aforementioned thrust faults. These weathering pockets were subsequently filled by alluvial, very finely washed Paleogene fat clay.

One such pocket with alluvial Tertiary clay was located 1 km from the village of Lebedyansky. At this place the Tertiary clay, having penetrated deeply along an expanded disjunctive fracture, proved to be laminated by small movements along the thrust. Since nearby, where the alluvial clay of the pocket lies outside the disjunctive zone, in its footwall or hanging wall, it is an ordinary massive, undisturbed clay, the platy texture of the clay must be explained by slight movements along the displacer, i.e., one must admit comparatively young tectonic movements that affected the lower parts of the Paleogene deposits of Kuzbass. This, incidentally, appears to be confirmed by other observations as well, for example, on the Ya. River.

6. Post-Tertiary dislocations along the eastern margin of the Kuznetsk Basin.

The post-Tertiary tectonic life of Kuzbass is recorded in its river terraces and their deposits, which have as yet been insufficiently studied, but which even now have revealed to us the complexity of this life. In the present note I wish to draw attention to the fact that Quaternary tectonics in Kuzbass, as in all of Siberia, apparently expressed itself not only in the formation of extensive, gentle plicative structures of the wave type, but also in some places in disjunctives. Such disjunctives have recently been established in the Altai; Kuzbass, apparently, is no exception to the general picture.

The examination of this question must begin from afar, with the geomorphology of the Mrassa River, with its Great Rapid, situated between its right tributaries, the Tashelga and the Kizes, at the sharp turn of the river from a meridional to a latitudinal direction. This majestic rapid, whose roar drowns out the human voice, formed at the site of the Porozhinsky granite pluton, which is cut across by the Mrassa River. At this place the river bed is blocked by enormous granite boulders, through which the waves of the enraged river rush furiously. It has cost many brave men their lives when they attempted to descend the rapid by boat.

The length of the most dangerous part of the rapid is 4 km. Over this distance the level of the river drops by 35 m. Despite the enormous energy of the river, now being fruitlessly expended in the struggle with the boulders, the formidable river has nevertheless been unable, even by a fraction of a kilometer, to shift this step of its longitudinal profile upstream.

A striking contrast to the Great Rapid is presented by another reach of the Mrassa River (Fig. 5), where it is almost as much

is considerable, and where it forms a sharply expressed incised meander. Despite the fact that the meander is cut into the bottom of the Quaternary valley, despite the fact that here the river cuts through granite for a greater distance than at the Bolshoi Rapid (5 km instead of 4 km), despite all this, there is here not a trace of the impressive picture of the Mrassu Rapid: traveling by boat, one sees here the usual picture for the Mrassu of a generally calm, swift mountain river, flowing at low water on average at a speed of 5–6 km per hour. Such a striking contrast, other conditions being equal, is naturally explained by the presence of a disjunctive fault with uplift of the eastern part of Gornaia Shoria by approximately 35 meters relative to the western part; moreover, this movement evidently took place along the Tashelga disjunctive zone.

It is still premature to accept this conclusion definitively. It is necessary to check along the Mrassu itself (along one of the ancient terraces) whether there are other indications of the post-Pliocene disjunctive fault being established here. But even now one may cite, in support of our hypothesis, the following fact. The Bolshoi Taz River, taking its rise on Mount Mustag, crosses the aforementioned Tashelga zone, southwest of which it flows over metamorphic shales of the Kondoma Formation, which is part of the Porozhinsk block. And it turns out that 5 km above the northwestern boundary of the horst, on the Bolshoi Taz River, a waterfall is observed. Since the river cuts through much more yielding rocks (shales instead of granite), the waterfall, under regressive bottom erosion, has evidently had time to migrate upstream from this boundary for a considerable distance. In this connection we note that the Bolshoi Taz waterfall is situated within an entirely homogeneous thickness of shales and, of course, does not owe its formation to a barrier of more resistant rocks.

Thus, the Bolshoi Rapid of the Mrassu River was apparently located at the Tashelga fault. If, however, we trace the latter northward, we shall see that there it becomes a disjunctive fault bounding the Paleozoic of the Kuzbass on the east.

Of course, we do not mean to say that the age of this disjunctive fault is Quaternary. No, it is very ancient; along it, in particular, took place the intrusion of a series of intrusions, for example, Devonian syenites and adamellites. But the life of this disjunctive fault revived again later as well: for example, when telemagmatic solutions deposited cinnabar at certain points of this fault, and, finally, the last noticeable movement occurred in late Quaternary time (after the formation of the above-mentioned incised meanders), as the Mrassu Rapid bears witness to us.

List of Cited Literature

1. Kuzmin A. M.—Materials on the stratigraphy and tectonics of the Kuznetsk Alatau, Salair, and Kuznetsk Basin. Publications of the Siberian Branch of the Geological Committee, Vol. VII, issue 2, 1928.

2. Nalivkin D. V.—The doctrine of facies. Conditions of sediment formation. 1932.

3. Radugin K. V.—On relict tectonic structures of xenoliths of erupted rocks. Manuscript. 1938.

4. Radugin K. V.—On Salair folding. Proceedings of the Academy of Sciences of the USSR, 1938.

5. Sivov A. G.—Geological description of the Mountain Shoria, Koraiskii planchet. 53°30′—53°45′ N lat., 88°—88°30′ E long. from Greenwich. Tomsk. 1932.

6. Usov M. A.—Phases and cycles of tectogenesis of the West Siberian Territory. 1937.

7. Usov M. A.—Elements of the tectonics of the Kuznetsk Coal Basin. Library of the Mining Journal, 1924.

8. Yavorskii V. I. and P. I. Butov.—The Kuznetsk Coal Basin. Transactions of the Geological Committee, new series, issue [[unclear: issue number]]. 1922.

1. In the USSR it was discovered by the author several years ago in the collection of B. F. Speransky from the area of the town of Orlinaya. ↩