NEW DATA ON BURIED SOILS OF THE SOUTHWESTERN PART OF THE KUZNETSK BASIN, BASED ON THE EXAMPLE OF THE KOLMOGOROVO SECTION

E. D. Rubchikova, E. K. Chuguevskaya

(PRESENTED BY THE SEMINAR OF THE DEPARTMENT OF HISTORICAL GEOLOGY)

A constant feature of the loess strata widely distributed in the periglacial zone is the presence within them of buried soil horizons. The latter are usually understood as dark-colored (humus), clay-enriched, or leached (of carbonates) layers in loess strata that have preserved, to one degree or another, a soil profile. This sometimes makes it possible, already in field conditions during visual study, to assign buried soils to a definite genetic type. Many researchers in our country and abroad use buried soils in subdividing loess strata (Velichko, 1961; Veklich, 1969; Moskvitin, 1930, 1963, 1966; Volkov, 1971, and others). I. P. Gerasimov, A. I. Moskvitin, A. A. Velichko, and other researchers attach great importance to buried soils in paleogeographic reconstructions.

A. M. Kuzmin (1929) and E. V. Shumilova (1932) wrote about the presence of buried soils in the Pleistocene deposits of the Kuznetsk Basin (mainly along the valley of the Tom’ River). In the last two decades much attention has been given to the study of Quaternary deposits (Fainer, 1967, 1969; Mikhalchenko, 1967, and others); however, there is not a single work devoted to the special study of buried soils as the most important paleogeographic and stratigraphic indicators of the Quaternary sequence.

In the present work we describe the distribution, conditions of occurrence, and soil profile of buried soils in the southwestern part of the Kuznetsk Basin, using the Kolmogorovo section as an example. Studies of the Quaternary deposits of the southwestern part of the Kuznetsk Basin have been carried out by us since 1965 along natural bank exposures of the Tom’ River on the stretch from the town of Mezhdurechensk to the village of Shorokhovo, in boreholes of the Uropskoye, Karakanskoye, and Taldinskoye deposits, and also in coal pits of the Prisalaïr’e area (Listvyansky, Krasnobrodsky, Novosergeevsky, Bachatsky, Kolmogorovsky, Mokhovsky, Gramoteinsky). This large body of factual material made it possible to reveal the main regularities in the areal and sectional distribution of buried soils and to give a preliminary conclusion about their genetic types.

Buried soils in Quaternary deposits occur everywhere, both on watersheds and in river valleys on all terraces, except floodplains and the first terraces above the floodplain. The number of buried-soil horizons in sections of the subaerial cover of terraces varies from one to seven; moreover, the older the terrace, the more hori-

horizons of buried soils. Some of these buried soils are traced in coastal outcrops for several kilometers [8].

On watershed areas the greatest number of buried soils (up to six) in the Pleistocene section has been noted in places where the Paleozoic basement subsided in the area of the Salair region (Bachat section). On projections of the ancient relief the number of buried soils decreases sharply, or they are entirely absent. Individual buried soils on watersheds can be traced for tens of kilometers in coal sections. According to the available paleontological data and stratigraphic position in the Pleistocene section, most of the buried soils belong to the Late Pleistocene, and only the two lower horizons probably belong to the Middle Pleistocene [6, 8]. The bone remains of large mammals found were assigned by E. V. Alekseeva to the Upper Paleolithic complex and dated to the Late Pleistocene [1].

The buried soils studied, depending on their confinement to various relief elements, are represented by different genetic types: on elevated parts of watersheds and subaerial covers of river terraces by various chernozems, while in relief depressions, lower parts of terrace covers, and on slopes they are replaced by meadow, bog, and gray forest soils [1, 6, 8].

Let us consider the characteristic features of the buried soils of the southwestern part of the Kuznetsk Basin using the example of the Kolmogorovo section (Fig. 1), located on the right bank of the Inya River, near the settlement of Kolmogorovo. The section of Quaternary deposits in the area of the named settlement was first studied by I. A. Volkov (1971). He described an 8-meter loess sequence with one buried soil. I. A. Volkov attributes the time of its formation to the last, post-interglacial phase of watering of Western Siberia, i.e., regards it as an age analogue of the Sumino fossil soil (Volkov, 1971).

In studying the Kolmogorovo section we used morphological analysis with a detailed description of the entire genetic profile of the buried soils according to the scheme used by soil scientists in the study of modern soils. The morphological description was accompanied by a very detailed sampling (by a continuous furrow every 20–25 cm) for physicochemical analyses. Below we give a description of the section (from top to bottom):

1. Modern soil—leached chernozem (0.0–2.0 m)—has the following profile: A—0.00–0.60 m—dark gray, almost black; the structure is granular in the upper part and blocky below. The transition is “tongued.”

B₁—0.60–1.0 m—in the moist state has a dark-brown color, with humus infillings from the overlying horizon; the structure is blocky. The transition to the next horizon is gradual.

B₂—1.00–2.00 m—yellow-brown with a brownish shade, coarse-blocky structure, fine-pored, carbonate. Neoformations are present in the form of pseudomycelium. Some physicochemical characteristics of the modern soil are shown in Fig. 1.

A characteristic feature of it is the high humus content of horizon A—9.02%—and the sharp decrease in its content in horizons B₁ and B₂ to 0.5%.

1. Loess-like loam (0.2–3.0 m), yellow-brown, macroporous, with a high carbonate content (5.3–10.6%). According to granulometric (microaggregate) analysis, it belongs to heavy coarse-silty loams (Fig. 1).

2. Buried soil (3.0–5.0 m) is well traced along the entire section for approximately 500 m at a depth of 3.0–3.5 m from the ground surface as a brownish-brown layer with a bluish-

Fig. 1. Diagram of the structure and material composition of the Quaternary deposits of the Komsomol’skii section.
1 — modern soil; 2 — loesslike loam; 3 — buried soil; 4 — grayish-gray clay; 5 — clay shale; 11 — granulometric composition; 6 — fine sand; 7 — fine gray sand; 8 — 0.01–0.005 mm; 9 — 0.005–0.001 mm; 10 — <0.001 mm; 6 — >0.05 mm; 7 — 0.05–0.01 mm; 8 — 0.01–0.005 mm; 9 — 0.005–0.001 mm; 10 — <0.001 mm.

Visible labels in the diagram:

• Granulometric composition (microaggregate)
• pH
• CaCO₃
• Ebuf
• Absorption capacity
• mg-eq

Fig. 2. Diagrams of the granulometric and chemical composition of the Pleistocene soils of the Kolyma section. Legend: buried soils in the section (from top to bottom): a — I buried soil; b — II buried soil; c — III buried soil; d — IV buried soil (for symbols see Fig. 1).

Labels in the diagrams:

• \(p_k\)
• \(p_H\)
• \(p\)
• Humus, %
• Total exchange capacity, mg-eq
• \(\mathrm{CaCO_3}\), %
• Granulometric composition, %

with a light-gray interlayer in the upper part. A detailed morphological study makes it possible to assume the presence of a soil bed consisting of two buried soils, one lying upon the other. Between them there is a small yellow-brown interlayer of loess-like loam, 15 cm thick.

The structure of the upper buried soil is as follows:

A — 3.00–3.30 m — light gray, fairly dense, weakly porous, with traces of plant-root passages.

B (g) — 3.30–3.60 m — grayish-bluish with bluish-gray spots of gley and ocherous smears. In the moist state it is dense, viscous, sticky, and smears.

P — 3.60–3.80 m — parent material, loess-like yellow-brown loam with ocherous spots.

In comparison with the overlying loess-like loam, this soil has a heavier particle-size composition—28% clay; the amount of coarse silt decreases sharply—to 46.0%. Carbonates are almost half as abundant as in the overlying loess-like loam—5.8%; however, the humus content increases to 1%, and the absorption capacity to 27 mg-eq per 100 g of rock (Figs. 1 and 2a).

In the bed of buried soils under consideration, the genetic profile of the lower soil, unlike the upper one, is thicker (3.8–5.0 m). Its structure is as follows:

PA — 3.80–4.00 m — brownish-gray loam with a whitish tint (because of abundant accumulation of carbonates), slightly compacted, porous; the transition is gradual and distinct.

A — 4.00–4.50 m — dark brown with a brown tint, of lumpy structure, carbonate, loose, permeated by passages of plant roots.

P — 4.50–5.00 m — yellow-brown with a brown tint, with humus streaks in the form of tongues penetrating into the underlying loess-like loam as well. The latter abounds in small mole burrows filled with humified material.

According to physicochemical analyses, humus, absorption capacity, and the content of the clay fraction have their highest values in humus horizon A (humus—1.5%, absorption capacity 25 mg-eq per 100 g of rock, clay—22.0%; Figs. 1 and 2a). In horizon B and in the underlying loess-like loam, the content of these physicochemical characteristics drops sharply.

The formation of the described bed of buried soils was probably connected with two stages of soil formation under different climatic conditions. The lower soil (3.8–5.0 m), which in morphological features resembles a chernozem, formed during the climatic optimum of the interstadial under conditions of a relatively dry, warm climate. This is indicated by the presence of carbonates in all soil horizons.

The upper soil (3.0–3.8 m), having a thin profile with traces of intense waterlogging, probably formed under excessive moistening in conditions of a colder climate corresponding to the end of the interstadial—the beginning of the interglacial. Judging by its stratigraphic position in the section, the presence of a gleying horizon, and its structure, this soil was also described by I. A. Volkov (1971).

1. Loess-like loam (5.0–6.9 m), yellow-brown, macroporous, coarse-silty (65%), medium-textured (clay fraction 18%), carbonate (5.0%). The transition to the buried soil is uneven but clear.

2. Buried soil (6.9–10.5 m) with a very thick profile clearly differentiated into genetic horizons. It is readily traceable throughout the section in the form of a continuous brown-brown layer.

The humus horizon of this soil is difficult to separate from the humus-transitional

original. The latter differs in the form of distribution of humus (in the form of streaks), and also in a more compact composition.

Its structure and morphological characteristics are as follows:

PA—6.9–7.30 m—brownish-gray with a whitish shade (owing to the abundant accumulation of carbonates of secondary origin), slightly compacted, weakly porous; the transition to the underlying horizon is noticeable.

A—7.30–8.30 m—dark brown with a chestnut shade, weakly porous, loose, cloddy-dusty. The lower boundary is uneven but noticeable; the transition is by pockets and tongues that enter the underlying horizon.

B₁—8.30–9.30 m—chestnut-brown with indistinct signs of nutty structure, more compacted than the upper horizon. Mycelium of humus is visible, especially in the upper part at a depth of 8.3–8.8 m. The lower boundary is uneven, but clearly noticeable.

B₂—9.30–10.5 m—yellow-brown, dense; the structure is blocky-cloddy; accumulations of carbonates are observed in the form of streaks and spots. In this horizon, as well as in the underlying loesslike loam, large mole burrows filled with humus material are encountered.

On the basis of the morphological characteristics of this soil (a thick humus horizon A depleted of carbonates, a humus-illuvial horizon B₁, an illuvial-carbonate horizon B₂, structure, and others), it may be assumed that this is a thick chernozem, the formation of which proceeds under conditions of a very warm and humid climate.

1. Loesslike loam (10.5–11.9 m), in the upper part light, yellow-gray, silty, weakly calcareous, light, macroporous; downward it becomes darker, denser, heavier (Fig. 1).

2. Buried soil (11.9–14.0 m), by morphological characteristics, belongs to soils of the chernozem type. It has a well-differentiated profile:

PA—11.9–12.3 m—a transitional horizon from loesslike loam to the buried soil, yellow-brown, porous, calcareous.

A—12.3–13.1 m—dark brown with a chestnut shade, of cloddy-angular structure, slightly compacted, non-calcareous, with rare large pores, the walls of which are filled with humus material.

B₁—13.1–13.5 m—yellow-brown loam, of indistinct prismatic structure, with inclusions of gravel, with bluish-gray gley spots and accumulations of humus material.

B₂—13.5–14.0 m—yellow-brown, darker, with small bluish-gray spots. In this horizon a large horizontal mole burrow (20 cm long) was encountered, filled with dark, more humified material. Some physicochemical characteristics of this soil are presented in the graphs (Figs. 1 and 2в).

In contrast to the two overlying buried soils, the soil profile of the third buried soil examined by us is completely leached of carbonates, except for a certain accumulation of CaCO₃ in the PA horizon (probably, CaCO₃ was leached from the overlying loesslike loam). It is possible that during the period of formation of this soil there was a more humid climate with excessive surface moistening.

1. Loesslike loam (14.0–15.0 m), yellow-brown, medium, coarse-silty, calcareous (Fig. 1).

2. Moist clay of gray-green color (15.0–16.0 m).

3. Buried soil (16.0–17.6 m):

16.00–16.60 m—chestnut-brown cloddy loam. The transition to the underlying horizon is by tongues.

16.60–17.2 m—rusty-brown, compacted heavy loam, with a fine nutty structure.

17.2–17.6 m—yellow-brown with a brownish tint, less dense than the overlying structureless loam.

The soil type has not yet been established. It is characterized by a brownish-buff color with noticeable signs of ferruginization and the complete absence of carbonates. The soil was probably subject to flooding (as evidenced by the presence of a layer of gray-green clay overlying the soil).

1. Yellow-brown loam, non-carbonate (17.6–18.5 m).

2. Bluish-gray clay, moist, dense, viscous (18.5–19.5 m).

3. Clay shales (19.5 m).

The distribution of buried soils in the section described depends on the behavior of the basement; in places where the basement rises, the two or three lower soils pinch out. Everywhere, for hundreds of meters along the entire quarry, the youngest buried soil can be traced; it extends for tens of kilometers in other quarries of the southwestern part of Kuzbass as well. By analogy with other sections of the southwestern part of the Kuznetsk Basin, the age of the upper three buried soils is preliminarily determined by us as Late Pleistocene. The lower soil is possibly of Middle Pleistocene age.

Thus, it has been established that the buried soils in the Pleistocene deposits of the southwest of the Kuznetsk Basin are predominantly chernozemic, are widespread everywhere, and, with more detailed study, should be used in the compilation of stratigraphic schemes.

LITERATURE

1. E. V. Alekseeva, E. D. Ryabchikova. On the question of the age of the loess-like rocks in the environs of the city of Novokuznetsk. Questions of the Geography of Siberia, Tomsk, TSU Publishing House, 1973, No. 8.

2. E. V. Arinushkina. Manual for the Chemical Analysis of Soils. Moscow, MSU Publishing House, 1970.

3. M. V. Veklich. Stratigraphy of the Loess Formation of Ukraine and Neighboring Countries. Kiev, “Naukova dumka,” 1968.

4. I. A. Volkov. Late Quaternary Subaerial Formation. Moscow, “Nauka,” 1971.

5. A. M. Kuz’min. Materials toward the subdivision of the glacial period in the Kuznetsk-Altai region. Proceedings of the West Siberian Geological Committee, VIII, issue 2, Tomsk, 1929.

6. A. A. Kurbatova, E. D. Ryabchikova, E. K. Chuguevskaya, V. M. Kabanova. Lithological and palynological characterization of the Quaternary deposits of the Uropskoe brown-coal deposit in Kuzbass (Uropskii–Yuzhnyi sector). Proceedings of the TPI, vol. 217, Tomsk, TSU Publishing House, 1971.

7. E. V. Shumilova. Terraces of the Tom’ River in its middle course. Materials on the Geology of the West Siberian Territory, issue 8, Tomsk, 1934.

8. A. I. Lavrent’ev, E. D. Ryabchikova, E. K. Chuguevskaya. The Bedarevskii Pleistocene section in Kuzbass. Materials for the Conference of Young Scientists and Postgraduate Students. Novosibirsk, “Nauka,” Siberian Branch of the USSR Academy of Sciences, 1969.