Lithological and Mineralogical Characteristics of the Uropsky Reference Section of Quaternary Deposits in Kuzbass

E. D. Ryabchikova, E. K. Chuguevskaya

(Presented by Professor A. G. Sivov)

The area in which the section of Quaternary deposits described below was studied is located in the central part of Kuzbass, on the right bank of the Inya River, and is intermediate between the Prisalaïr and eastern parts of the distribution of Quaternary deposits of the Kuznetsk Basin. In the Prisalaïr depression, Pleistocene deposits were studied by B. F. Mikhalchenko (1966). He established that the thickest and stratigraphically most complete Pleistocene sections are exposed in the northwestern part of the Prisalaïr depression and reach 80–100 m. The upper part of the section of Quaternary deposits in this area is represented by mantle loess-like loams and clays, the age of which is dated to the Upper Pleistocene.

No special lithological-mineralogical studies of Quaternary deposits in the area of the Uropsky deposit have been carried out up to the present. In this connection, a comprehensive study of reference sections of Quaternary deposits in this area is especially important. Near the village of Urop (2 km to the southwest), borehole 1187 exposed one of the reference sections of Quaternary deposits of Kuzbass, expressed as follows from top to bottom:

1. Buried soil, degraded, brownish-gray; by mechanical composition, a heavy loam, weakly ferruginized along channels left by plant roots . . . . . . . . . . . . 2.

2. Heavy loam, loess-like, lacustrine-alluvial, dusty yellow, silty, carbonate, porous, with rare channels left by plant roots; in places horizontal bedding is noticeable.

3. Buried soil, heterogeneous through the layer, strongly ferruginized, as a result of which it acquires a brownish-brown color at the top. By mechanical composition it is mainly clay; at the base—a heavy loam of yellowish-brown color, penetrated by numerous channels left by plant roots, noncarbonate . . . . . . . . . . . . 3.0.

4. Heavy loam, loess-like, yellowish-brown, pale yellow, carbonate, silty, bedded, lacustrine-alluvial . . . . . . . . . . . . 8.4.

5. Buried soil, degraded; by mechanical composition, a heavy loam of dark-brown color, with a characteristic fine oolite-like texture, weakly carbonate and noncarbonate, slightly ferruginized . . . . . . . . . . . . 2.

6. Brown clay, dense, slightly sandy, slightly ferruginized, with black specks of soot, white inclusions of gypsum; toward the end of the interval, finely horizontally bedded . . . . . . . . . . . . 3.5.

7. Interval without core . . . . . . . . . . . . 20.

8. Jurassic deposits—pebble beds, sandstones, siltstones with the flora Phoenicopsis . . . . . . . . . . . .

Changes in the values of absorption capacity, pH, calcium carbonate content, and humus in the section, as well as graphs of mechanical and mineralogical composition, are shown in Fig. 1. The results of analyses, visual and microscopic studies show that the three identified members of loess-like loams have certain common features.

1. A clearly expressed loess-like appearance (macroporosity, siltiness, friability, carbonate content, with the exception of the upper noncarbonate layer).

2. A sharp predominance of the silty fraction (0.05–0.005 mm) according to microaggregate analysis: in the lower member—52.0–66.5%; in the middle—55.2–80.2%; in the upper—63.8–69.4%; including the “loess” fraction (0.05–0.01 mm) [according to N. I. Kriger, 1965], respectively: in the lower, 38.0–51.0%; in the middle—48.4–69.3%; in the upper—49.9–57.4%; that is, by this feature they may be assigned to loess rocks.

3. Comparatively high values of carbonate content (by calcimeter): in the middle member—4.86–8.0%; in the lower—6.91–9.4%.

4. The value of absorption capacity (by the method of L. I. Kulchitskii) generally remains low: in the lower member—18.8–27.8 mg-equiv per 100 g of rock; in the middle—20.4–26.8 mg-equiv; in the upper—16.9–20.9 mg-equiv.

5. The humus content in the loess rocks is low and amounts (by the method of I. V. Tyurin): in the lower member—0.24–0.31%; in the middle—0.22–0.29%; in the upper—0.28–0.51%.

The principal minerals of the heavy fraction in the loess rocks are magnetite (in the lower, 18.2–22%; in the middle—19.5%; in the upper—21.6%); minerals of the epidote group (in the lower—39–46.7%; in the middle—42%; in the upper—44.5%); green hornblende, respectively: 15–16.9%; 14%; 16.5%; and, in small quantities, there are also: zircon (2–5%); anatase, leucoxene, rutile, tourmaline, garnet, limonite.

The light fractions consist mainly of quartz (lower member—

Fig. 1. Diagram of the structure and material composition of the Quaternary deposits of the Uropsky section in borehole 1187 (Belovsky district, Uropsky P site). Lithology: 1—soil layer; 2—loess-like loams; 3—buried soils; 4—loams and clays, bluish-gray, dark-gray, silty; 5—clays, brown, dark-brown; 6—interval without core; 7—sandy-gravel-pebble deposits; 8—sandstone; 9—mollusk shells. Mechanical composition: 10—\(>0.05\) mm; 11—\(0.05\)–\(0.01\) mm; 12—\(0.01\)–\(0.005\) mm; 13—\(0.005\)–\(0.001\) mm; 14—\(<0.001\) mm. Mineralogical composition: 15—ore minerals; 16—leucoxene, anatase, sphene, rutile; 17—zircon, tourmaline, garnet; 18—hornblende; 19—epidote; 20—apatite, biotite, etc.; 21—quartz; 22—feldspars; 23—micas; 24—aggregates of clay minerals and rock fragments.

40–50%; average—32%; upper—54%), in smaller amounts feldspars respectively: 15–23%; 18%; 27%; micas (6–12%; 8%; 5%) and clayey rock fragments. The mineral grains, as a rule, are unrounded, more rarely semi-rounded, and usually have an irregular shape.

Study of the clay minerals by units with the aid of thermal analysis shows a heterogeneous mineral type of clays: in the lower unit, montmorillonite–hydromica (with kaolinite as an admixture); in the middle unit, montmorillonite–kaolinite; in the upper unit, hydromica (with montmorillonite and kaolinite).

The bulk chemical composition of the loess-like loams by units is as follows (in %): lower unit—SiO\(_2\) 57.71–59.64; Al\(_2\)O\(_3\) 14.27–14.88; Fe\(_2\)O\(_3\) 5.24–5.39; CaO 5.21–6.62; MgO 1.86–1.98; Na\(_2\)O 1.0–1.30; K\(_2\)O 2.05–2.15; middle unit SiO\(_2\) 59.74; Al\(_2\)O\(_3\) 14.43; Fe\(_2\)O\(_3\) 5.06; CaO 5.46; MgO 1.86; Na\(_2\)O 1.05; K\(_2\)O 2.10; upper unit—SiO\(_2\) 65.97; Al\(_2\)O\(_3\) 15.0; Fe\(_2\)O\(_3\) 5.41; CaO 1.25; MgO 1.88; Na\(_2\)O 1.45; K\(_2\)O 2.0. In addition, FeO (0.53–0.71) and MnO are present. The value of the silica coefficient

\[ K_i=\frac{\mathrm{SiO}_2}{\mathrm{Al}_2\mathrm{O}_3} \]

for these units is, respectively: 4.03; 4.14; 4.33, which indicates the accumulation of colloidal quartz, intensive degradation of loess rocks, and an increase in climatic humidity (the more humid the climate, the higher the value of \(K_i\)) [Lomonovich, 1955].

Spectral analysis of the loess rocks, carried out by E. V. Kurysheva, yielded the following results (in %): Ti = 0.6; Mn = 0.1–0.2; V = 0.03–0.05; Ni = 0.001–0.005; Cr = 0.03–0.05; Co < 0.001; Zn = 0.01–0.02; Cu = 0.001–0.003; Pb = 0.001; Ba = 0.003–0.007. Mo, Sn, and others are noted among the admixtures. The average content of trace elements in the section is approximately constant.

Four horizons of buried soils have been distinguished in the section. They are characterized by the following: a darker color in comparison with the loesslike loams (see description); an increased humus content (up to 3.07%); the absence or a small amount of calcium carbonate (as determined with a calcimeter); an increased absorption capacity (as determined by FEK—M—56, 27.8–37.2 mg-eq per 100 g of rock); the presence of numerous passages from plant roots, filled with humus and iron oxides, and humus streaks in the subsoil layers. The reaction of the medium was determined as the pH of a suspension of the rock on LPU—01; the pH values are 7.53–7.95. In granulometric composition, the buried soils of all four horizons are heavy loams and clays and differ from the loess rocks by a lower content of the silty fraction (34.4–54.3%), a somewhat higher content of the clay fraction (up to 38.2%), and a barely noticeable lumpy-granular structure.

In the mineralogical composition of the heavy and light fractions, the buried soils differ little from the loesslike loams. We note only a somewhat increased content of minerals of the epidote group (46.1–52.3%) and quartz (43–52%) relative to the underlying loesslike loams of the lower and middle members. The principal minerals of the colloid-dispersed part of the buried soils, established by thermal analysis, are beidellitized hydromica, hydromica with an admixture of montmorillonite, and kaolinite.

The characteristics of the grain composition and chemical properties of the greenish-gray loams and brown clays (members 3 and 9 according to the description) are given in Fig. 1, and we shall not dwell on them in detail. In mineralogical composition of the heavy and light fractions, the rocks of these members basically do not differ from the other rocks of the section. The principal minerals of the colloid-dispersed part of the greenish-gray loams are hydromica, montmorillonite, illite, kaolinite, calcite, and quartz. The presence of organic matter is noted. The mineral type of the brown clays is hydromicaceous (with montmorillonite, kaolinite, and illite).

As is evident from the data presented above on the mineralogical composition of the heavy fraction, in the loess rocks of all three members minerals unstable and only slightly resistant to weathering sharply predominate (magnetite, apatite, epidote, amphiboles, garnet, etc.). A. K. Larionov points out that “this group of minerals is of interest from the standpoint of resolving questions of the genesis of deposits” [Larionov et al., 1959]. As N. I. Kriger notes, “similar data compel I. D. Sedletskii, V. P. Anan’ev, and A. S. Ryabchenkov to reject the soil-eluvial hypothesis and to accept the eolian hypothesis of the origin of loess. However, on the basis of these data it would be more correct to assert not an eolian, but a broader subaerial origin of the rock under arid or cold conditions. V. V. Popov [1957] rightly notes that when rock is formed under conditions of a cold and arid climate, intensive weathering does not occur and, probably, even unstable minerals may be preserved” [Kriger, 1965].

Taking into account all that has been set forth above, one may conclude that the loess rocks of the Uropsky section are polygenetic subaerial formations, in the process of whose formation several factors took part, the chief of them being: water, wind

and secondary soil processes. It is not possible to resolve this question specifically on such limited material.

For the time being, the age of the Quaternary deposits of this section can be judged only from the literature.

Yu. V. Kuropatkin, E. A. Ponomareva, and others, in a 1960 report, write that “in the deposits of loess-like loams of the Tom River valley, isolated finds of mammal bones were encountered at various times. Thus, in 1956 A. G. Dubok mentions the discovery of a mammoth in 1938 in the loess-like loams of the city of Novokuznetsk (the Sotsgorod district, at a depth of 1.5 m). On the basis of these finds, the age of the loess-like loams should not be raised above the Middle Pleistocene \((Q_2)\). To be sure, there are opinions of V. A. Martynov, M. G. Kipiani, and some other researchers, who consider the age of these deposits to be Upper Quaternary \((Q_3)\)” [Kuropatkin et al., 1960]. Taking into account the high position of the loess-like deposits in the section, we share the opinion of the latter authors and provisionally date the age of the loess-like loams of the Uropsky section to the Upper Pleistocene. Summarizing what has been set out above, the following conclusions may be drawn:

1. The Uropsky section of Quaternary deposits is represented mainly by loess rocks.

2. The uniformity of the mineralogical and chemical compositions of the deposits of the section indicates the constancy of the source areas of the Kuznetsk depression during Quaternary time.

3. Mineralogical analysis of the heavy and light fractions shows that the principal rock-forming minerals are quartz and feldspars. Among the heavy fraction, the main characteristic minerals are magnetite (18.2–21.6%), minerals of the epidote group (39–46.7%), and green hornblende (14.0–16.9%); that is, they are mainly minerals unstable during weathering.

REFERENCES

1. N. I. Kriger. Loess, Its Properties and Relation to the Physico-Geographical Environment. Nauka Publishing House, Moscow, 1965.

2. Yu. V. Kuropatkin, E. A. Ponomareva, L. I. Efimova, O. Yu. Kachuro. Biostratigraphy of Quaternary Deposits of the Kuznetsk Basin and the Southwestern Margin of the Chulym-Yenisei Depression. Novokuznetsk, 1960.

3. A. K. Larionov, V. A. Priklonskii, V. P. Anan’ev. Loess Rocks of the USSR and Construction Properties. Gosgeoltekhizdat, 1959.

4. M. I. Lomonovich. Colloidal minerals, microaggregate structure, and subsidence of loess of the Trans-Ili Alatau. Problems of the Geology of Asia, vol. II, Publishing House of the Academy of Sciences of the USSR, 1955.

5. B. F. Mikhal’chenko. On the stratigraphy and lithology of Quaternary deposits of the western part of the Kuznetsk depression. Proceedings of TPI, vol. 151, 1966.