Comparative Lithological Characteristics of the Balakhon Series in the South and North of the Kuznetsk Basin

A. N. Volkova

The Balakhon Series of the Kuznetsk Basin, composed mainly of thick sandy-clayey deposits with coal seams often of workable thickness, is of great practical interest. However, its stratigraphic position has still not been definitively established. The lithology of this series is also insufficiently developed. Therefore, in 1954 the Lithology Laboratory of Moscow State University, under a contract with the West Siberian Geological Administration, began a study of the material composition of the rocks of the Balakhon Series of the basin, with the aim of determining its genesis. As for the stratigraphic correlation of the sections of the series, it was accepted, with minor changes, according to the data of the local geological exploration parties of the Administration and of Kuzbassuglegeologiya, which provided great assistance in the work being carried out.

During the indicated period, sections of the Balakhon Series were studied in the following districts: Tom-Usa, Chumysh, Aralichevo, Shushtulep, Kemerovo, Biryulino, Zmeinka, and Anzhero-Sudzhensk. The Chumysh, Tom-Usa, and Zmeinka districts were studied by the author; Shushtulep and Aralichevo by M. N. Shatrova; Biryulino, Anzhero-Sudzhensk, and Kemerovo by A. A. Lisovenko, G. A. Butuzova, and V. I. Koporulin (Fig. 1). Overall scientific supervision was carried out by G. F. Krasheninnikov.

The study of the Balakhon Series in each district was carried out according to the following plan. In the field, mainly on the basis of core material, the vertical section of the series was described in detail; outcrops exposing deposits of the series were studied; and, where a sufficient number of boreholes was available, individual parts of the section were traced over the area.

In describing the section, a detailed macroscopic characterization of the rocks was given; considerable attention was paid to their textural features, the distribution and preservation of flora and fauna, the distribution of concretions through the section, their composition, morphological features, and so on.

During laboratory processing, the material composition of the clastic rocks was studied comprehensively. To determine accurately the structure and degree of sorting, granulometric analyses were carried out on relatively loose clastic rocks, since analyses of densely cemented rocks that have undergone preliminary mechanical disaggregation are, as a rule, distorted because of abrasion of grains of decomposed effusives, the content of which in the rocks of the Balakhon Series is considerable.

The petrographic composition of clastic rocks, the composition of the cement, and the types of cementation were studied in thin sections for a number of samples. The percentage content of individual components of the rock was determined on an integration stage.

Fig. 1. Overview map of the areas of work, 1954–1956. 1 — boundaries of the Balakhon Series; 2 — areas of work: 1 — Tom-Usa (a — Kumzas deposit, b — Berezovo deposit), 2 — Chumysh, 3 — Biryulinsk, 4 — Anzher, 5 — Kemerovo, 6 — Zmein.

Due attention was devoted to the study of the mineralogical composition of the heavy fractions from clastic rocks, since, according to the data of V. I. Marchenko, it is of great significance also for the Balakhon Series of the Kuznetsk Basin.

As shown in the works of N. V. Logvinenko [6] for the Donets Basin and I. D. Zkhus [5] for the Moscow Basin, the study of clayey rocks from coal-bearing basins is of great importance for studying genesis, since they are very sensitive reagents to the environment of sedimentation and to the subsequent transformation of the sediment and rock. Thus, it has been established that kaolinite–hydromica associations of clay minerals are characteristic of continental facies, whereas montmorillonite and beidellite associations are characteristic of marine facies (of an alkaline sedimentation environment). In addition, it has been shown that the mineralogical composition of clays changes substantially depending on the degree of diagenesis. Thus, in deposits where seams of highly metamorphosed coals occur, only kaolinite–hydromica associations of clay minerals are developed, whereas in deposits with seams of less metamorphosed coals the clay associations may be more varied, depending on their original composition.

Taking into account the great genetic significance of clays, during the laboratory processing of the material we comprehensively studied clayey rocks and clayey fractions from clastic rocks and from clayey-carbonate concretions. The set of methods for studying the clayey fractions included:

1) staining of clay suspensions with organic dyes (the method of N. E. Vedeneeva and M. F. Vikulova [2]);

2) determination of the refractive indices of clay minerals in oriented aggregates (according to M. F. Vikulova [3]);

3) thermal analysis;

4) chemical analysis;

5) electron-microscopic studies.

The study of the composition, structure, and distribution of concretions, as shown by A. V. Makedonov for the Pechora Basin [7], is of great importance for clarifying the genesis of coal-bearing deposits and for stratigraphic subdivision. He established that the most magnesian ferruginous-carbonate concretions are characteristic of a marine environment, whereas pure siderite varieties are typical mainly of continental facies. Therefore, we paid considerable attention to concretions both in the field and during laboratory processing.

The study of concretions involved great difficulties, caused by their microgranular structure and by considerable admixtures of clayey material.

The investigation of concretions proceeded along several lines. The substance of the concretions as a whole was studied, i.e., the carbonate and clayey parts together; for this purpose, detailed descriptions of thin sections, thermal analysis, and chemical analysis were carried out. The carbonate substance itself was studied by determining the refractive indices of small pure carbonate grains in immersion and by staining in the specimen. The insoluble, predominantly clayey, constituent of the concretions was studied by the method of staining with organic dyes and by determining refractive indices in oriented aggregates.

Thus the laboratory processing of the collected rock material was, as far as possible, carried out comprehensively, since only a detailed integrated study of the material composition of the series, of the conditions of its occurrence and its areal variation, with due regard for the flora and fauna encountered in it, makes it possible to approach an understanding of its genesis on a sound basis.

Lithological Characteristics of the Balakhon Series

The Balakhon series, cropping out in a broad belt along the margins of the Kuznetsk Basin, constitutes the lower horizons of its many-kilometer-thick succession of coal-bearing deposits. Stratigraphically, according to the scheme adopted at the conference on the unification of the stratigraphic schemes of Siberia, it includes deposits from the Middle Carboniferous through the Lower Permian inclusive and is divided into three formations: the Ostrog, Lower Balakhon, and Upper Balakhon. The average thickness of the series is 2200 m.

The rocks of the Balakhon series differ clearly from the underlying deposits of the marine Lower Carboniferous, whose upper horizons are represented by strongly carbonatized sandstones and siltstones of a characteristic gray-green color. They are characterized by good sorting and rounding of the grains; up to 40% of the rock consists of quartz grains; feldspars are abundant, while the number of grains of effusive material barely reaches 10%, which is not characteristic of the rocks of the Balakhon series. In the clay fraction of the marine Lower Carboniferous deposits of the Tom-Usinsk region, montmorillonite is present, which again distinguishes these rocks from the rocks of the Balakhon series of the same region.

The Kuznetsk formation overlying the Balakhon series differs little macroscopically from the Balakhon series. An almost complete absence of coal seams is noted in it.

There are also certain differences in composition. Thus, in the clastic rocks of the Kuznetsk suite, the amount of grains of effusive material is somewhat lower than in the rocks of the Balakhon series, with a constant amount of quartz grains (22–24%).

The lower part of the Kuznetsk suite differs from the Upper Balakhon suite in the composition of its concretions, for which greater clay content is noted (up to 50%), and an increased role of Mg and Ca in them, so that they approach ferruginous dolomites or strongly magnesian siderites (sideroplesites).

The clay fractions from the clastic and clay rocks are represented by beidellite (Zmeinsky district) or by beidellitized kaolinite–hydromica (Tom-Usinsk district) associations, which again substantially distinguishes this suite from the Upper Balakhon suite. Thus, by lithological features the Balakhon series is rather clearly separated from the underlying and overlying deposits. The indicated division of the Balakhon series into suites, based on paleontological data, is confirmed by the fairly distinct lithological features of the latter.

The Ostrog suite, varying in thickness from 300 to 600 m, is characterized by insignificant coal content (up to 1.3%), a somewhat increased content of coarse- and medium-clastic rocks (up to 50%) in comparison with the Lower Balakhon suite, and by the order of alternation of rocks. Within the suite in the Tom-Usinsk district, three members may be distinguished: a lower one, predominantly medium- and coarse-clastic, with a structure of members (cycles) from coarse-clastic to clayey rocks, more rarely to coal; a middle one—more fine-grained, where, on the contrary, a coarsening of material is observed from fine clayey aleurolite to fine-grained sandstone; and, finally, the upper part of the section, represented by an alternation of coarse-grained sandstones with gravel, conglomerates, and occasionally fine-grained rocks and thin (0.1–0.2 m) coal seams.

T. I. Protsvetalova [10], who studied the Ostrog suite of the basin in detail, notes the same threefold structure for it in other districts as well.

The petrographic composition of the clastic rocks of the Ostrog suite is characterized by an increased content of quartz (up to 30%) and quartzite material, with an insignificant number of grains of effusive rocks; only at the very base of the suite, according to T. I. Protsvetalova’s data, does the role of effusive grains increase substantially.

The clay fractions from the clastic and clay rocks have been studied only from the upper part of the suite and are represented by kaolinite–hydromica associations for the south of the basin and by beidellite associations for the north (Zmeinsky district).

The concretions of the Ostrog suite have been insufficiently studied; only for the Tom-Usinsk district can one point to the broad development of siderite concretions with a considerable amount of Mg; more rarely there occur thin interbeds of carbonate rock, compositionally approaching aleurolitic limestone.

The Lower Balakhon suite, with a thickness from 500 to 1000 m, is subdivided into the Mazurovka and Alykaevka subsuites. The suite is characterized by a predominance of fine-clastic rocks in comparison with the overlying suite (Fig. 2). It is characterized by an alternation of thin interbeds of fine, often clayey, dark-gray aleurolite and lighter coarse aleurolite (of the lenticular-layer type). Sometimes thicker interbeds of these rocks are also noted.

These rocks are characterized by fine horizontal and gentle bedding, sometimes wavy; in fine-grained sandstones and coarse aleurolites, fine cross-bedding is observed, in most cases caused by fine plant detritus.

Biryulinsky   Zmeinsky   Tom-Usinsky

Column headings in the lithological sections:

• Formation and suite
• Principal horizons and subhorizons
• Lithological column
• Curves of the mechanical composition
• Mineralogical composition of rocks

Visible suite and horizon labels include:

• Mazurovskaya suite
• Antibeska suite
• Prokopyevskaya subsuite
• Inskaya subsuite
• Kemerovskaya subsuite
• Kuznetsk suite
• Uskat suite
• Ilyinskaya subsuite
• Alykaevskaya subsuite
• Tarsminskaya suite
• Mikhailovskaya subsuite
• Yerunakovskaya subsuite

Petrographic composition according to thin sections

1 — quartz;
2 — feldspars;
3 — fragments of effusive rocks;
4 — siliceous rocks;
5 — various undetermined grains;
6 — cement.

Fig. 2. Lithological characteristics of the Balakhon series of the Biryulinsky, Zmeinsky, and Tom-Usinsky districts of Kuzbass.

Rocks: 1 — conglomerates, gravelites, breccias; 2 — coarse- and medium-grained sandstones; 3 — fine-grained sandstones; 4 — coarse aleurolites; 5 — fine aleurolites; 6 — argillites; 7 — carbonaceous argillites; 8 — coal. Bedding: 9 — horizontal; 10 — horizontally wavy; 11 — oblique; 12 — oblique-wavy; 13 — cross-bedded. Concretions: 14 — siderite; 15 — siderite with a slight admixture of CaCO₃; 16 — siderite with a considerable admixture of magnesia; 17 — siderite with an admixture of CaCO₃; 18 — ferruginous dolomite; 19 — iron-carbonate spherulites. Organic remains: 20 — carbonized branch fragments; 21 — impressions of leaves and stems; 22 — fauna.

The thickness of the intercoal members is very variable, as is their composition. Sandy rocks do not always appear in them; often the grain size of the material does not exceed fine siltstone. In most cases the coal is enclosed in clayey and silty rocks; only in the upper part of the Alykaevskaya subformation do medium-grained sandstones lie directly on the coals. The number of coal seams is rather large; in the south of the basin they are mainly thin, while in the north their thicknesses are considerably greater.

The composition of the clastic rocks is characterized by an approximately identical content of grains of effusive rocks and other components (quartz, feldspars, quartzite, etc.). Strong carbonatization of the fine-clastic rocks is noted, especially near interbeds of strongly clayey (marly) limestones, for example from the Alykaevskaya subformation (XLVII–XLIX seams) of the Tom-Usa district.

The mineralogical composition of the heavy fractions from rocks of the Lower Balakhon series is very variable both in vertical section and areally. However, the composition of the heavy fractions has a number of common features for the southeast and north of the basin, namely: 1) a somewhat reduced zircon content in comparison with the Upper Balakhon series, and 2) a substantial amount of phlogopite and chlorite, especially in the Alykaevskaya subformation (Fig. 3).

The composition of the clay fractions from the clastic and clayey rocks of the series, despite all its diversity—from kaolinite to beidellite mineralogical associations—is characterized by the predominance of the latter (Fig. 4).

Ferruginous-carbonate concretions are characteristic of the Lower Balakhon series. The latter differ somewhat in their composition: in most cases they contain an admixture of magnesium and approach sideroplesites. For some concretions from this subformation the presence, and sometimes the predominance, of calcite is characteristic (Biryulinsky and Zmeinsky districts). Only in the most coal-saturated parts of the section are purer siderite concretions and concretionary interbeds present (Fig. 5).

Upper Balakhon series, including the Ishanovo-intermediate, Kemerovo, and Usyatskaya subformations, is of great practical interest because of its coal content (the coal-bearing coefficient for the Kemerovo subformation is 8–19%), especially in the south and southeast of the basin. Its average thickness is about 1000 m.

For this series, for the basin as a whole, one should note the increasing role of medium- and coarse-clastic rocks in comparison with the underlying series. Breccias, gravelites, and conglomerates appear.

These rocks are characterized by large-scale oblique bedding, usually caused by changes in the grain size of the material. Fine-clastic rocks have fine horizontal, horizontal-wavy, or gently inclined oblique and cross-bedding.

A very variable structure and thickness of the intercoal members are noted. Sandstones or conglomerates often lie on the coal with erosional contact.

The coal content of the subformations differs for individual districts of the basin. If in the south the Usyatskaya subformation is the most coal-bearing, then in the north it is often practically coal-free; the upper part of the Kemerovo subformation and the upper part of the Ishanovo-intermediate subformation are the most coal-bearing (Fig. 2).

The composition of the sandy rocks is characterized by an increased role of grains of effusive material. The quantity of fragments of strongly destroyed sedimentary rocks is considerably greater than in the rocks of the Lower Balakhon series.

The mineralogical composition of the heavy fractions of the Upper Balakhon suite is highly variable both in the vertical section and over the area. The heavy fractions of this suite are characterized by an increased content of zircon, as well as by a sharp increase in the role of garnet in the rocks of the Ishanovo–intermediate subsuite (Fig. 3).

The clay fractions from clayey and clastic rocks are represented mainly by kaolinite and kaolinite–hydromica associations; only in the Zmeinka area, in the Ishanovo–intermediate subsuite, is montmorillonite widely developed, and beidellitized kaolinite–hydromica clay associations from the same subsuite of the Bryukhanovo area are noted (Fig. 4).

The Upper Balakhon suite is characterized by concretions and concretionary interbeds (especially numerous for the Zmeinka area) of siderite; moreover, the concretions of the Usyaty subsuite are characterized by a lower magnesium content in comparison with the concretions of the Kemerovo and Ishanovo–intermediate subsuites. Siderite concretions with a considerable admixture of CaCO₃ are fairly widely distributed in the Ishanovo–intermediate and Kemerovo subsuites. In the coal-bearing parts of the section of the suite, horizons of spherulitic structure are known (Fig. 5).

Despite all the complexity and diversity of the structure of the Balakhon series, in its petrographic composition for the basin as a whole a number of common features can be distinguished.

The polymictic composition of the clastic rocks, whose grains may be represented by: the main mass of granite porphyries and acid effusives, usually strongly altered; pelitized micrograined quartz–feldspar aggregates; quartzites and microquartzites; chloritized micrograined aggregates; porphyrites and the main mass of basic effusives, their grains often chloritized; argillites; clayey and sericitic-clayey shales; siltstones and sandstones; quartz, often with undulatory extinction (usually its grains are somewhat corroded; in all likelihood, it is a product of the disaggregation of quartzites); feldspars (potassic varieties predominate, almost always pelitized; plagioclases are somewhat fewer, and they are rather often sericitized and pelitized); chalcedony; micas: muscovite, more rarely biotite, with especially abundant sericite, although in part it is of secondary origin and develops after clay minerals; chlorite (usually developed on grains of effusive rocks, but independent grains are sometimes encountered).

In the vertical section there is a fairly regular increase in quartz and quartzite material from the Upper Balakhon suite to the Ostrog suite; this is especially clearly expressed for the southeastern part of the basin.

In the heavy fraction from clastic rocks there predominates a complex of stable minerals: zircon, garnet, tourmaline, picotite, apatite, titanium-bearing minerals, etc. Minerals of the metamorphic group (according to Baturin) are present in insignificant quantities. Minerals of the amphibole and pyroxene group occur as single grains and by no means always.

The mineralogical composition of the heavy fractions in the vertical section and over the area often undergoes substantial fluctuations over very short distances, which greatly complicates, and sometimes makes impossible, the correlation of individual sections, especially in the south and north of the basin¹); however, there are also general regularities in the mineralogical composition of the heavy fractions (Fig. 3): an increased content of chlorite and phlogopite in the Alykaevka subsuite, with a reduced content of zirco-

¹) It is impossible at present to extend these conclusions to the entire basin as a whole, since the Balakhon series along the western margin of the basin has as yet been lithologically little studied.

Fig. 3. Distribution of minerals of the heavy fractions (in %) in the Balakhon Series of Kuzbass.

1 — zircon; 2 — garnet; 3 — tourmaline; 4 — titanium-bearing minerals; 5 — picotite; 6 — chlorite; 7 — phlogopite.

Visible labels in the diagram:

• Suites
• Supra-suites
• Kuznetsk
• Tom–Usa
• Bungur–Chumysh
• Elga
• Barzas

Stratigraphic subdivisions shown at left:

• Upper Balakhon
• [[unclear: suite name]]
• Usyat
• Kemerovo
• Ishanovo–Intermediate
• Lower Balakhon
• Ananyino
• Mazurovo
• Ostrog

Scale markings shown for the columns: 20, 40, 60, 80.

; an increase in the role of zircon in the Upper Balakhon suite, with a very considerable increase of garnet in the Ishanovo-intermediate subsuite.

The role of various, predominantly iron-carbonate concretions is substantial. Since concretions are of great importance for determining the genesis of the strata, we shall dwell on their characteristics in greater detail.

Concretions and concretionary interbeds of the Balakhon series are represented by various, predominantly ferruginous carbonates. The concretions vary greatly in size, from several centimeters in diameter to large ones whose diameter somewhat exceeds a meter. The form of the concretions is usually rounded, somewhat flattened, and sometimes also lentil-shaped. The concretionary interbeds, often well sustained, have a thickness from several centimeters to several tens of centimeters.

The concretions and concretionary interbeds are confined mainly to siltstones, silty argillites, and more rarely fine-grained sandstones; concretions also occur in sandy rocks, but in this case there is often no certainty that they have not been redeposited and, in essence, should not be regarded as pebbles.

The concretions are, to one degree or another, contaminated with detrital and clayey material; usually the more silty and sandy varieties of them are associated with the more sandy clastic rocks.

By composition, the following groups of concretions may be provisionally distinguished (Fig. 5):

1. Pure siderite concretions with varying amounts of clastic material; usually they are widely developed in the Usyat subsuite of the entire basin, but they also occur in coal-bearing members and lower horizons (the Alykaev subsuite of the Zmeinogorsk district and the Ishanovo-intermediate subsuite of the Chumysh district).

2. Siderites with an admixture of magnesium (sideroplesites and varieties close to them) have a considerable vertical distribution. They occur in the Kemerovo, Ishanovo-intermediate, and Ostrog subsuites of the Tom-Usa district; in the Chumysh district they are known mainly in the Kemerovo subsuite. In the north of the basin the more magnesian varieties of siderite are developed; they are widely distributed in the Lower Balakhon suite, the Ishanovo-intermediate subsuite, and the Kemerovo subsuite.

3. Siderite concretions with an admixture of calcium are known, but often the amount of calcium is such that they cannot be regarded as calcic siderites; in this case the presence of a mixture of ferruginous carbonate and calcite must be assumed. Similar concretions are recorded for the two lower subsuites of the Upper Balakhon suite of the Biryulinsk district, and more rarely for the Chumysh and Tom-Usa districts.

4. Calcareous-ferruginous concretions are known from the Lower Balakhon suite of the Biryulinsk district; they occur sporadically in deposits of the same suite in the Tom-Usa district.

5. Pure calcite concretions and interbeds of limestone, admittedly strongly clayey, occur in the Alykaev subsuite of the Tom-Usa district, where they reach a thickness of several meters and can no longer be considered concretionary. Pure calcite concretions are known from the Mazurov subsuite of the northern districts of the basin.

Changes in the Balakhon Series over the Area of the Basin

Although the Balakhon series of the Kuznetsk Basin is characterized by a number of features inherent to it for the basin as a whole, it undergoes substantial changes over the area. Its thickness, coal content, structural features of the rocks, and the mineralogical composition of the clayey ro—

types, concretions, heavy fractions, and cement of the clastic rocks differ considerably over the area of the basin. Therefore, tracing individual subformations over the area causes great difficulties, especially when correlating sections of the south and north of the basin.

The characteristics of changes in the thicknesses of the series over the area, as well as its coal content and coal quality, have been analyzed in considerable detail in a number of works, and therefore are not touched upon in the present article [1; 8].

Changes in the structural features of the rocks of the Balakhon Series are subject to a definite regularity: a general decrease in the coarseness of the material is observed from the south—southeast toward the north—northwest. This is expressed to a lesser degree in the Lower Balakhon Formation, but even with its more or less homogeneous structure for the basin as a whole, the same regularity may be noted. If, for the Tom-Usa district, the presence in it of interbeds of medium-grained, more rarely coarse-grained sandstones, sometimes with subordinate interbeds of gravelites, is noted, then already for the Chumysh district the absence of material coarser than medium-grained sandstones is characteristic. In the north of the basin, especially in the Biryulinsk district, medium-grained sandstones are almost absent. In this district a broad development of fine siltstones and argillites is noted, especially the former, whereas in the Tom-Usa district the section of the formation is dominated by frequent interbedding of coarse and fine siltstone (laminae).

The sharpest changes in the structure of the clastic rocks are observed for the Upper Balakhon Formation and especially for the Kumzas deposit of the Tom-Usa district, where the Kemerovo and Usyat subformations consist almost entirely of coarse-clastic rocks: fine-pebble conglomerates with interbeds of gravelites associated with them, and coarse-grained sandstones; more rarely, interbeds of finer-grained rocks and coal appear in them. Several kilometers to the west (north of the Berezovo deposit), the same subformations are represented by various sandstones with lenses of conglomerates and gravelites; breccias are also observed. In the upper coal-bearing part of the section, the role of coarse siltstones interbedded with fine-grained sandstones and finer-grained rocks increases (up to 50%).

The Upper Balakhon Formation of the southwestern parts of the Tom-Usa district has basically the same structural features, especially the Usyat subformation, which can be traced for a distance of 50–55 km almost without substantial change; however, within it as well, toward the southwest and west, a certain decrease in the coarseness of the material is apparent.

In the Upper Balakhon Formation of the Zmeinka district the role of sandy rocks is significant, especially in the Kemerovo member, where an almost 180-meter package of sandy rocks with interbeds and lenses of conglomerates and gravelites occurs. The structure of this package recalls the structure of rocks of the same age in the Tom-Usa district.

The structure of the Upper Balakhon Formation of the Biryulinsk district differs substantially; there, the clastic rocks do not exceed medium-grained sandstones in coarseness, and fine-grained sandstones with interbeds of various siltstones and argillites predominate.

Thus, for the Upper Balakhon Formation of the Biryulinsk district, very substantial differences from rocks of the same age on the more eastern and especially southeastern margins of the basin are apparent. The change over the area is observed not only in the structure of the clastic rocks, but accordingly also in their texture.

The composition of the grains of the clastic (sandy) rocks changes little over the area, whereas the composition of the cement and the type of cementation undergo major changes. Thus, for the southeast of the basin, a film type of cementation and cementation of the pore-filling type are characteristic, rarely—contact cementation,

Districts: Tom–Usa; Bungur–Chumysh; Emelyanovo; Biryulya; Anzhero.

Suite: Upper Balakhon; Lower Balakhon.
Subsuite: Kuznetsk; Usyat; Kemerovo; Kazankovo–Markino; Anzhero; Mazurovo; Ostrog.

Fig. 4. Composition of clay fractions from clastic and clayey rocks of the Balakhon series of Kuzbass.

Associations of clay minerals. From clastic rocks: 1—kaolinite; 2—kaolinite–hydromica; 3—montmorillonite; 4—beidellite. From clayey rocks: 5—kaolinite; 6—kaolinite–hydromica; 7—kaolinite–hydromica, beidellitized; 8—montmorillonite; 9—beidellite.

more abundant cement is almost never encountered. In composition the cement is clayey-siliceous, clayey-sericitic, and more rarely carbonate.

The clastic rocks of the Chumysh district are distinguished by the complete absence of clay cement, with a very broad development of abundant sericitic cement, which probably arose at the expense of clayey material; this may be connected with the initial stages of metamorphism. This was reflected especially clearly in the composition of the coals and, correspondingly, in the clayey material of the cement.

Similar in composition are the cements of the sandy rocks of the Biryulinsk district, where sericitic-clayey and clayey-chloritic cements predominate, often with abundant newly formed micas. In this same district carbonate, chalcedony, and quartz cements are also noted.

For the Zmeinsk district, carbonate cements are characteristic, and more rarely clayey-siliceous cements; the former are often very abundant (basal type of cementation).

In describing the lithology of the Balakhon Series, certain regularities common to the basin were indicated in the distribution of minerals of the heavy fraction; however, substantial fluctuations in the content of the remaining components of the heavy fraction often make the correlation even of sections not greatly distant from one another extremely difficult, especially along the southeastern margin of the basin.

Thus, in the west of the Kumzas deposit, in the Usyatsk Subsuite, the role of corundum is very great in a number of samples, whereas in rocks of analogous age in the north of the Berezovsk deposit (a distance of 2–3 km) corundum is completely absent. This indicates very poor sorting of the material, which is not surprising given insignificant transport. Many such examples could be cited.

The mineralogical composition of the heavy fractions of the south and north of the basin differs especially sharply.

The mineralogical associations of the upper part of the Upper Balakhon Suite in the south of the basin are determined by a fairly stable zircon–tourmaline complex with a considerable quantity of titanium-bearing minerals. In the north of the basin, deposits of the same age are also characterized by a zircon–tourmaline complex, but already with a significant amount of picotite, which is sometimes the predominant mineral (Zmeinsk district). For this part of the section the role of garnet is also great; the latter is practically absent in the south of the basin (Tom–Usinsk district). Fluctuations in the content of other minerals are also very substantial.

Correlation of the mineralogical composition of the heavy fractions of the Lower Balakhon Suite is still more complicated. Such sharp differences in the mineralogical composition of the minerals of the heavy fractions make it possible to suppose that two different terrigenous-mineralogical provinces existed for the north and south of the basin.

The study of clay fractions from clastic rocks and clayey rocks of the Balakhon Series shows, for most districts of the basin, a rather uniform composition of clay minerals (Fig. 4). Kaolinite and kaolinite–hydromica mineral associations predominate; only for the Zmeinsk district, as a whole, are beidellite and montmorillonite clay associations characteristic. This circumstance, it would seem, could be connected with the degree of diagenesis of the rocks, which is very clearly reflected in the degree of metamorphism of the coals of the indicated district.

However, if such a dependence does exist, it is considerably more complex. The presence of montmorillonite in the sandy and aleurolitic rocks of the Lower Marine Carboniferous, of beidellitized kaolinite in some samples of the Mazurovsk Subsuite and the lower part of the Kuznetsk Suite of the Tom–Usinsk district, and also the presence of kaolinite and kaolinite-

Fig. 5. Composition of concretions in the Balakhon Series of Kuzbass.

Visible labels in the diagram:

• Suite
• Subsuite
• Regions
• Tom–Usa
• Bungur–Chumysh
• Inya
• Biryulinsk
• Ostrog Suite
• Lower Balakhon Suite
• Mazurovo Subsuite
• Alinkevskaya Subsuite
• Upper Balakhon Suite
• Ishanovo–Promezhutochnaya Subsuite
• Kemerovo Subsuite
• Usyat Subsuite
• Kazankov Subsuite

Designations of concretions:
1 — sideritic; 2 — sideritic with a slight admixture of Mg; 3 — sideritic with a significant admixture of Mg (sideroplesites); 4 — sideritic with an admixture of CaCO₃; 5 — calcitic; 6 — ferruginous-dolomitic; 7 — interbeds of argillaceous limestone; 8 — horizons of ferruginous-carbonate spherulites.

the hydromica clayey association in the rocks of the upper Balakhon subseries of the Zmeinka district, with the broad development in the section of montmorillonite and beidellite, indicate that the mineralogical composition of the clays is connected not only with diagenesis, but in a number of districts reflects the conditions of formation of the sediment and may thus be an important genetic indicator, although the degree of diagenesis leaves its imprint on the mineralogical composition of clays and argillites.

The presence of beidellitization in the lower Balakhon and Kuznetsk formations is apparently connected with the existence of brackish-water basins, which is also confirmed by the corresponding fauna. The wide development of beidellite–montmorillonite clayey associations in the Zmeinka district should possibly be related to the slow accumulation of material, when the reverse process of stadial alteration of clayey matter in an alkaline environment can be manifested more fully; this, apparently, is not sufficiently clearly reflected under more rapid accumulation and burial of sediments. According to A. V. Kutyukov, a brackish-water fauna is characteristic of the Zmeinka district¹.

The kaolinite and kaolinite–hydromica composition of the clay mineralogical associations in the southwest (Chumysh district) and north (Biryulinsk and Anzherka districts) of the basin, where coals are observed that are more highly metamorphosed than on the eastern margin, probably already fully reflects diagenetic changes in the clayey matter.

Thus, far from all districts of the basin have a mineralogical composition of clayey associations that indicates the conditions of formation of the sediment.

The variation of concretions over the area of the basin is also determined by fairly clear regularities: toward the north of the basin the role of the isomorphic admixture of Mg in siderite concretions increases, and siderite concretions with a considerable admixture of calcite become more widely distributed; numerous (Biryulinsk and Zmeinka districts) lenticular interbeds of clayey limestone and calcite concretions occur, although interbeds of clayey limestone are also known from the Alykaevka subformation of the Tom–Usa district (Fig. 5).

The study carried out of the Balakhon series of the Kuznetsk Basin makes it possible to refine existing ideas concerning its genesis. The lithological differences of the Ostrog, lower Balakhon, and upper Balakhon formations testify to changes in the facies settings during their accumulation.

The structure, the character of coal-bearing capacity, textural and structural features, as well as the character of concretions, the presence of calcareous-clayey interbeds, and the composition of the clay fractions from the clastic and clayey rocks of the lower Balakhon formation testify to the broad development at that time of basinal facies, as V. I. Yavorsky correctly points out in his works. The investigations carried out of clayey rocks and carbonate concretions allow one to suppose the presence of brackish-water basins, with the degree of salinity increasing toward the north of the basin (see the distribution diagrams of carbonate concretions and clayey matter).

Material entered the basin from the Kuznetsk Alatau, since it is precisely in this direction that the grain size of the material of the clastic rocks increases.

In Upper Balakhon time the depositional environment changed substantially. The thick beds of various sandstones widely developed in the Upper Balakhon suite, often with coarse bedding, sometimes with lenses and interbeds of conglomerates and usually replacing, along a sharp boundary, beds of fine-grained rocks with coal seams, indicate sharp fluctuations in facies conditions.

The sandstones and conglomerates may be assigned to the facies of flat alluvial fans, especially since in them one can trace coarsening of the material in the direction toward the source area. It may be assumed that fine-grained clastic rocks with coal seams accumulated under basinal conditions, which were often replaced over broad areas by swamping. The basins were fresher in comparison with those of Lower Balakhon time, but in the north of Kuzbass they retained brackish conditions for a longer time (the Ishanovo–Intermediate subsuite). A broad development of alluvial facies in the Upper Balakhon suite, as indicated by E. A. Perepechina [9], has not been found.

Thus, in the Balakhon series of the Kuznetsk Basin, basinal facies are widely developed (especially in Lower Balakhon time), as are facies of flat alluvial fans and swamp facies, undergoing regular changes both in the vertical section and areally.

REFERENCES CITED

1. Belyanin N. M. and Khalfin L. L. Stratigraphic scheme of Kuzbass, adopted by the 1954 conference (general characterization). Problems of the Geology of Kuzbass, 1, Ugletekhizdat, 1956.

2. Vedeneeva N. E., Vikulova M. F. A method for studying clay minerals with the aid of dyes and its application in lithology. Gosgeolizdat, 1952.

3. Vikulova M. F. Determination of the mineralogical composition of clay particles of 0.001 mm with the aid of immersion liquids. Collection Weathering Crust, issue 1, Publishing House of the Academy of Sciences of the USSR, 1956.

4. Zaritskii P. V. Chemical-mineralogical characterization of carbonate concretions in deposits of various facies of the Middle Carboniferous of the western part of the Donets Basin. Scientific Notes of Kharkov State University, vol. LXXIII, 1956.

5. Zhus I. D. Clay minerals of coal-bearing deposits of the southwestern part of the Moscow Basin. Soviet Geology, coll. 46, 1955.

6. Logvinenko N. V. History of sedimentation in the Donets geosyncline. Scientific Notes of Kharkov State University, vol. LXXIII, 1956.

7. Makedonov A. V. Concretions of the Vorkuta suite (an attempt at using concretions for the study of sedimentary sequences). Author’s abstract of dissertation. IGN, Academy of Sciences of the USSR, 1954.

8. Molchanov I. I. and Khalfin L. L. Stratigraphy of the coal-bearing deposits of the Kuznetsk Basin. Soviet Geology, coll. 46, 1955.

9. Perepechina E. A. Lithological characteristics of the upper parts of the Balakhon suite of the south of the Kuznetsk Basin. Collection in memory of P. I. Stepanov, 1952.

10. Protsvetalova T. N., Sarycheva T. G., Sokolskaya A. N. On the Lower Carboniferous age of the Ostrog suite of the Kuznetsk Basin. Proceedings of the Academy of Sciences of the USSR, geological series, No. 2, 1956.

Moscow State University
named after M. V. Lomonosov

1. For a faunistic characterization of the Balakhon series of the Zmeinka district, see the work by R. N. Benediktova published in this volume. (Editor’s note.) ↩