Lithological and Palynological Characteristics of Quaternary Deposits of the Uropsky Coal Deposit in Kuzbass (Uropsky Southern Site)

A. A. Kurbatova, E. D. Ryabchikova, E. K. Chuguevskaya, V. M. Kabanova

(Presented by Professor A. G. Sinovym)

On the watershed of the Inya and Urop rivers in Kuzbass, Quaternary deposits are widely developed. Their most complete section, with a thickness of 45–49 m, confined to a subsidence of the basement, was exposed by boreholes 1066 and 1062 of the Inya exploration line, drilled by the Uropskaya Geological Prospecting Party of the Kuzbassuglegeologiya trust.

The results of the lithological and palynological study of this section, which may be regarded as a reference section on the right bank of the Inya River, are presented in the present article.

The section described lies within the southern geomorphological district of Kuzbass, with a hilly-valley relief developed on gentle brachyfolds composed of coal-bearing deposits of the Permian and Jurassic systems (Fainer, 1967). There are no natural exposures in this area from which the structure of the Quaternary-deposit section could be established.

The Quaternary deposits at the Uropsky Southern site are subdivided into several lithological members. The upper part of the section (members 2–4, Figs. 1, 2) is composed of light, yellowish-brown to pale loess-like loams, carbonate-bearing, silty, homogeneous, porous, with one buried soil horizon within them and a second at the base of the loess-like sequence. The light yellowish-brown loams may be termed loess-like not only on the basis of external morphological features (after Kriger, 1965), but also according to the results of laboratory analyses. Characteristic of the granulometric composition of these deposits is the predominance of the silty (52.81–72.5%) fraction (according to microaggregate analysis), and among the latter—the predominance of coarse (“loess,” after Kriger, 1965) dust over fine dust (Fig. 1). In terms of the content of the clayey (less than 0.005 mm) fraction, the loess-

Fig. 1. Diagram of the structure and material composition of Quaternary deposits of the Uropsky southern site according to borehole 1066.

Legend to Figs. 1—2: Lithology: 1—soil layer; 2—loess-like loams and clays of the upper member; 3—loess-like loams and clays of the lower member; 4—buried soils; 5—yellow-brown, grayish-brown loams and clays; 6—dark-brown, ferruginized loams and clays; 7—greenish- and bluish-gray, light- and dark-gray, silty loams and clays; 8—horizontally micro-laminated clay; 9—gravel–pebble deposits; 10—weathering crust of Paleozoic rocks; 11—siltstone; 12—plant detritus; 13—mollusk shells (gastropods); 14a—carbonate concretions; 14b—rock fragments. Mechanical composition: 15—0.05 mm; 16—0.05–0.01 mm; 17—0.01–0.005 mm; 18—0.005–0.001 mm; 19—0.001 mm. Mineralogical composition: 20—ore minerals; 21—leucoxene, anatase, sphene, rutile; 22—zircon, tourmaline, garnet; 23—hornblendes; 24—epidote; 25—biotite, chlorite, apatite, etc.; 26—quartz; 27—feldspars; 28—micas; 29—aggregates of clay minerals. Palynology: 30—sum of spores; 31—sum of pollen of woody plants; 32—sum of pollen of herbaceous plants.

The visible deposits are heavy silty loams and, more rarely, silty clays (Larionov et al., 1959). According to chemical analyses, the loess-like loams and clays differ clearly from the buried soils (Fig. 1) and are characterized by relatively higher carbonate content (2.6—6.2%), elevated pH values (8.0—8.3), a reduced absorption capacity (16.9—25.3 mg-eq) per 100 g of rock, and an insignificant humus content (0.21—0.38%, more rarely 0.45—0.52%).

The results of laboratory analyses made it possible to distinguish in the sect—

Fig. 2. Same-scale spore-pollen diagram of the Quaternary deposits of the Uropsky southern sector, borehole 1062
(compiled by V. M. Kabanova in 1967).

the same three buried soil horizons, which are visually difficult to distinguish. The buried soils differ substantially from the enclosing rocks not only in the properties listed above, of which the principal indicator for them is an increased humus content (0.48–1.45%), but also in an increase of the clay fraction to 31.3–40.50% (according to microaggregate analysis).

Between the middle (bed 5, Fig. 2) and lower buried soil horizons (bed 8), yellow-brown and grayish-brown loams and clays (bed 6) and dark-brown ferruginized clays (bed 7) were encountered, the latter being absent in the section of borehole 1066.

The lower part of the section studied is composed of gray, greenish-gray, bluish-gray to dirty-gray, sometimes darker and denser, sometimes lighter and looser silty clays (“blue” clays) (beds 9–12, Fig. 2, and beds 8–11, Fig. 1), more rarely loams of a lacustrine-bog facies, which fill irregularities of the ancient relief and were penetrated by all boreholes of the Inskaya exploration line. The thickness of the “blue clays” ranges from 2 to 28 m. Heavy silty loams and clays in the lower part of the section contain a large amount of plant detritus, which also accounts for anomalous values of humus content, up to 5.02%. Elevated absorption-capacity values, from 16.9 to 33.8 mg-eq per 100 g of rock, are consistent with the heavier grain-size composition (the clay fraction <0.005 mm amounts to 26.34–50.79%). A change in grain-size and mineralogical composition, as well as some-

of the chemical characteristics of the Quaternary deposits of this section with depth is characterized by the graphs given in Fig. 1.

In borehole 1066, at the base of the above-described “blue” clays there lies a thin (1.6 m) bed (bed 12) of sandy-gravel-pebble deposits with a clayey matrix, not encountered in any other borehole along the Inskaya exploration line. The pebbles reach sizes of 3 × 4 cm; composition: quartz, siliceous shale, quartzite, sandstone. The pebbles are well rounded, which indicates accumulation of this bed under channel conditions. In the sandy-clayey cement, admixtures of soot and coal are common.

At the base of the “blue clays” in borehole 1062 there are no pebbles, but numerous small fragments of bedrock and admixtures of soot are likewise encountered, which indicates the presence of erosion of the underlying coal-bearing deposits here as well.

The mineralogical composition is almost identical throughout the section of Quaternary deposits (Fig. 1), and the quantitative ratios of minerals vary little within individual beds; among the minerals of the light fraction, quartz and feldspars sharply predominate. The amount of quartz in the loess-like loams (35–45%) and buried soils (40–47%) remains more or less the same. The feldspar content decreases somewhat in the buried soils (16–22%) compared with the loess-like rocks (25–27%). In the other rocks of the section, the amount of quartz (50%) and feldspars (22–30%) remains constant, except at the very base of the section (bed 11), where the quartz content in dense greenish-gray clays, in places parallel thin-bedded, falls to 30%, and that of feldspars to 13%, owing to an increase in the amount of fragments of clayey rocks. The mineral grains are angular, more rarely subrounded, and have an irregular shape.

In the heavy fraction, epidote–zoisite noticeably predominates (41–60%); its amount either remains constant or increases somewhat in the buried soils (43–48%) and increases sharply at the base of the section (60%). The amount of hornblendes changes more sharply: from 23% in the upper bed of loess-like loams to 63% at the base of the section.

The principal minerals of the colloid-dispersed fraction are hydromica and kaolinite, more rarely beidellite, according to the results of staining with methylene blue and determination under an electron microscope. This is also confirmed by the values of absorption capacity (16.9–33.8 mg-eq per 100 g of rock) (Podgornaya, 1967).

The Quaternary deposits in the described section lack macropaleontological remains; therefore, we applied palynological analysis. Of 59 samples of Quaternary deposits from boreholes 1062 and 1066 that were studied, only 20 were richest in microremains; the loess-like loams are completely devoid of spores and pollen.

The section of borehole 1062 was characterized most fully; for it, it was possible to establish several spore-pollen complexes reflecting repeated changes in vegetation over time. The description of the distinguished complexes is given from the more “ancient” to the more “young” (Fig. 2):

At the base of the studied section (interval 41–42 m), moisture-loving forms constitute 46%; these are spores of Bryales, Botrychium sp., family Polypodiaceae, more rarely sphagnum mosses, and many indeterminate aquatic forms. The principal woody form here is pollen of Picea sp. (up to 10%); the herbaceous spectrum is represented by pollen of mixed herbs, with a slight predominance of goosefoots and wormwoods. Grains of Salix sp. and Tsuga sp. occur here in small numbers but consistently.

In the described assemblage, individual features are encountered that have previously been noted by a number of authors for Upper Pliocene—Early Quaternary assemblages of the central part of the West Siberian Lowland, the Pavlodar Irtysh region, and the foothills of Altai (Adamenko, Bukreeva, Efimova, 1966; Matveeva, 1953, 1958; Poleshchuk, 1966).

Upsection (interval 36–33.5 m), the quantitative ratio of the forms encountered changes sharply: the number of hygrophytes decreases, amounting to 9% of the total number of grains, with only Bryales being preserved; among woody plants, birch and alder pollen (4.5%) replaces spruce pollen; among herbaceous plants, most are Chenopodiaceae (40%) and wormwoods (15.5%); the number of mineralized wormwood grains (12.0%) increases significantly. Characteristic of the assemblage is the simultaneous presence in it of both hygrophytes and xerophytes.

The next assemblage (interval 33.5–22 m) is typically steppe: an absolute predominance of xerophytes (up to 80%) (Chenopodiaceae, wormwoods, ephedra); many mineralized wormwood grains (21–20%) and an insignificant amount of woody pollen (6.0–4.3%), both conifers and birch; the amount of spruce pollen falls to 2.5%, and sometimes it disappears entirely. A similar assemblage has been described by a number of authors for territories neighboring Kuzbass: G. F. Bukreeva, 1966; O. V. Matveeva, 1953, 1958; L. I. Efimova, 1966; A. A. Kurbatova, L. V. Aleksandrova; an analogous assemblage has been noted for the Middle Pleistocene deposits of the Irtysh region (1964).

The last assemblage (interval 18.5–8 m) is enriched in conifer pollen (up to 21.6%), among which spruce predominates (up to 15.8%). Birch pollen is encountered in it only singly. Among herbaceous plants, a high content of mineralized wormwood pollen is noted (up to 44.5%), less Chenopodiaceae (up to 31.6%), Compositae (9.9%), cereals (5.8%), etc.

Summarizing the above, it should be noted that there is a distinct repeated change of vegetation in the section studied. In the lower part of the section there is a typical forest-steppe assemblage with a weak degree of forestation. It is not uniform in its composition and probably characterizes a transitional moment in the change of vegetation from a moisture-loving type to a xerophytic one.

The next stage is a xerophytic steppe assemblage, confined to the middle part of the section, and in the upper part of the section there is a new change of plant cover—the phase of steppe spruce.

The data presented are still insufficient to date the deposits studied precisely; however, the material obtained testifies to a rhythmic change of plant cover in Quaternary time in Western Siberia (Grichuk, 1961).

REFERENCES

1. O. M. Adamenko, G. F. Bukreeva, L. I. Efimova. Spore-pollen spectra from deposits of the Kochkovskaya and Krasnodubrovskaya suites of the southern part of the Irtysh region. In: Collection of papers for the II International Palynological Conference in Utrecht. Publishing House “Nauka,” Moscow, 1966.

2. M. P. Grichuk. Main features of changes in the vegetation cover of Siberia during the Quaternary period. In: “Paleogeography of the Quaternary Period of the USSR,” Moscow State University Press, 1961.

3. N. I. Kriger. Loess, its properties and relationship with the geographical environment. Publishing House “Nauka,” Moscow, 1965.

4. O. V. Matveeva. On the history of vegetation of the Quaternary period in the Pavlodar Irtysh region. Transactions of the Institute of Geology, Academy of Sciences of the USSR, 1953.

1. O. V. Matveeva. Spore–pollen spectra of the Quaternary deposits of the Piedmont Altai. Publishing House of the Siberian Branch of the USSR Academy of Sciences, Geology and Geography, issue 1, 1958.

2. F. M. Mikhalchenko, A. A. Kurbatova, L. V. Aleksandrova. On the question of the stratigraphy and lithology of Quaternary deposits in the southwestern part of Kuzbass. Abstracts of reports to the All-Union Conference on the Study of the Quaternary Period, Novosibirsk, 1964.

3. G. A. Podgornaya. On the methodology for studying the mineralogical composition of clayey deposits. Vestnik MGU, No. 4, 1967.

4. V. P. Poleshchuk. Stratigraphy of the Quaternary deposits of the Tom–Chulym interfluve on the basis of spore–pollen spectra. Publishing House “Nauka,” 1966.

5. Yu. B. Fainer. The history of the development of the Kuznetsk Basin in the Mesozoic and Cenozoic eras. Dissertation for the degree of Candidate of Geological and Mineralogical Sciences. Novosibirsk, 1967.