NEW DATA ON THE SUBDIVISION OF QUATERNARY DEPOSITS IN THE NOVOKUZNETSK REFERENCE SECTION

E. D. Ryabchikova

(Presented by Prof. Dr. A. P. Sivov)

The purpose of this article is to present the results of a detailed study of a section of Quaternary deposits. It is exposed in a natural outcrop on the right bank of the Tom River in the city of Novokuznetsk, between the old and new bridges, and in a quarry worked into the surface of this terrace in the summer of 1967.

This outcrop was first described by A. M. Kuz’min (1929), who regarded the deposits of the lower part of the section as having been redeposited by a glacial river and, by age, assigned them to the second Mindel–Riss interglacial epoch. A. M. Kuz’min notes that in the Kuznetsk section the loess accumulations of the post-Pliocene lie sharply unconformably on the eroded surface of underlying deposits of the same post-Pliocene. Thus it follows that deposits accumulated in the first half of the second interglacial were later subjected to erosion. A. M. Kuz’min believed that the question of the age of the loess and its origin is very complex and controversial.

E. V. Shumilova (1934) gives a section of this terrace (the fourth according to her count) and, following A. M. Kuz’min in applying the Alpine stratigraphic scheme for subdividing Quaternary deposits, assigned “the entire thick sequence (up to 40–45 m) of fluvial and subaerial accumulations” to the second interglacial epoch. The main shortcoming of E. V. Shumilova’s studies is the absence of paleontological data for substantiating the age of the terrace deposits.

Yu. B. Fainer (1967) describes this terrace as the third above-floodplain terrace; its alluvial deposits he assigned to the Middle Pleistocene, while the covering loess rocks (to the latter he assigns only the upper 3–5 m) he recognized as being of Late Quaternary age.

Our studies substantially supplement the previously known materials on the stratigraphy, lithology, and especially the paleontology of this section. The upper part of the section, composed of loess rocks, was studied in a quarry exposing the Pleistocene sequence to a depth of 15–20 m. The lower part of the section, represented mainly by alluvial deposits of the third above-floodplain terrace, was studied in deep cuts in the bank bluff.

A composite section of the terrace alluvial and covering subaerial loess rocks is given in Fig. 1.

The socle of the terrace, represented by siltstones, sandstones, and argillites of the Upper Permian, rises 16–17 m above the level of the Tom River.

The subaqueous deposits of the terrace have a thickness of 15–17 m. They are crowned by a horizon of dark-brown buried soil (thickness 0.6 m), probably redeposited, since the boundaries of the soil with the enclosing loams are very sharp and no illuvial horizon is observed in the soil profile.

Fig. 1. Graph of the structure and composition of the Quaternary deposits of the Novokuznetsk section

Legend:

I. Lithology: 1—soil layer; 2—loess-like loams; 3—buried soils; 4—redeposited loess-like loams; 5—sand lenses; 6—yellow-brown, brownish-brown loams; 7—grayish-yellow loams with a greenish tint; 8—gravels; 9—rock fragments; 10—interbedding of sand and clay; 11—loessification; 12—bedrock; 13—shells; 14—places where rodent fauna was found; 15—place where large-mammal fauna was found; II. Microaggregate composition: 16—>0.05 mm; 17—0.05–0.01 mm; 18—0.01–0.005 mm; 19—0.005–0.001 mm; 20—<0.001 mm; III. Mineralogical composition: 21—magnetite; 22—leucoxene, anatase, sphene, rutile; 23—zircon, tourmaline, garnet; 24—amphiboles; 25—epidote; 26—apatite, muscovite, biotite, chlorite, etc.; 27—quartz; 28—feldspars; 29—micas; 30—carbonates; 31—rock fragments.

illuvial horizon. Above, with an erosional contact, lie alluvial-subaerial brownish-brown loams (thickness 4.6 m), likewise with a horizon of dark-brown buried soil in the upper part (thickness 0.6 m).

The upper part of the section is composed of loess rocks. The maximum thickness of the cover formations reaches 20 m.

Layer-by-layer facies–mineralogical analysis of the section made it possible to clarify the structure of the terrace and cover loess-like deposits, described by E. V. Shumilova (1934). Brownish-yellow and grayish-yellow loams with a greenish tint, of floodplain facies, overlying bedded sandy-loamy deposits with channel-facies gravel at the base, contain, in the interval 29.2–31.0 m, five interbeds of rubble, gravel, pebble, and sand. The clastic material contains many fragments of Permian bedrock sedimentary rocks, as well as quartz.

In the mineralogical composition of the alluvial deposits, the light fraction predominates (99.30–99.94%), the principal minerals of which are quartz (40–54%), feldspars (30–40%), micas (5–9%), and fragments of siliceous and clayey rocks (4–18%).

The principal minerals of the heavy fraction are epidote (39–48%), green hornblende (25–43%), and magnetite (9–19%). Present in smaller quantities are leucoxene (1%), anatase (1–2%), sphene (up to 1.0%), garnets (2%), tourmaline (1–3%), zircon (1–2%), apatite (up to 1.0%), and pyroxenes (up to 1.0%). Single grains of ilmenite, rutile, kyanite, and sillimanite were encountered. In the clayey (< 0.001 mm) fraction, according to the results of thermal analysis, hydromica with kaolinite predominates.

The bulk chemical composition of the deposits of the lower alluvial part of the section is characterized by the predominance of SiO₂ (59.0–63.2%), Al₂O₃ (14.61–16.19%), and Fe₂O₃ (4.53–6.99%). Present in smaller amounts are CaO = 2.09–4.46%; MgO = 1.78–2.49%; FeO = 0.64–1.92%; TiO₂ = 0.76–0.97%; K₂O = 1.80–2.20%; Na₂O = 1.25–2.50%; P₂O₅ = 0.142–0.275%; S = 0.01–0.05%.

According to the results of analysis of aqueous extracts, the dry residue is 0.060–0.110%; the salinization type is carbonate, and only at a depth of 33–35 m is it sulfate–carbonate. In degree of salinization, the deposits of the lower part of the section belong to the category of nonsaline deposits.

Above the second (middle) dark-brown chernozem-like buried soil, a loess stratum with one buried soil horizon within it is exposed in the quarry. The cover unit of yellowish-brown loess-like loams, up to 4 m thick, and the upper buried soil, exposed in the quarry at a depth of 1.5–5.0 m, wedges out toward the northern wall of the quarry. The buried soil lies inclined, repeating the ancient relief. The buried soil belongs to the chernozem steppe soils. This is indicated by the dark-brown color of the humus horizon, the great thickness of the profile (1.5), the high content of organic matter (Fig. 1), the character of the carbonate illuviation (carbonate salts in the form of tubules and white eyes), and also the presence of mole burrows in the subsoil layer. Above the buried soil, in places (in depressions formed by the relief of the soil surface), there occurs a thin (up to 0.5 m) wedging-out bluish-gray loam.

The lower part of the loess stratum (between the upper and middle buried soils) is composed of grayish-yellow loess-like loam. Away from the quarry wall, inclined bands resembling bedding, parallel to the upper buried soil, are noticeable in it. This, together with the presence of a large amount of sand, sometimes small lenses of sand with gravel and fine pebbles, and fragments of sedimentary rocks, makes it possible to suppose that the lower part of the loess stratum is composed of secondary, redeposited loess-like loams. In their accumulation ...

proluvial, deluvial, and, possibly, solifluction processes took part. Throughout the described bed of loess-like loams, mollusks of the “loess” complex have been found: Succinea oblonga Drap., Vallonia pulchella (Müll.), Pupilla muscorum (L.), Columella edentula Drap. (identified by I. A. Volkova). From this same bed, from depths of 4.0–4.5 m and 6.0–6.5 m below the present-day surface (at this place the cover bed of loess-like loams and the buried soil wedged out), bones of rodents were washed out: Lagurus lagurus Pall., 1773 (steppe lemming) and Microtus gregalis Pall., 1779 (narrow-skulled vole) (identified by A. B. Markina).

In this bed, in primary occurrence, part of the skeleton of a woolly rhinoceros¹ Coelodonta cf. antiquitatis Blum., bones of red deer Cervus elaphus Linn., steppe bison Bison priscus Boj., and a complete skull of the red fox Vulpes vulpes Linn. were discovered. At the bottom of the quarry, washed out of this same layer by water from the hydraulic monitor, were found bones of the aurochs Bos primigenius Boj., a fragment of a radius and a fragment of the lower jaw of a newborn mammoth Mammuthus primigenius Blum., a scapula of a large brown bear² Ursus cf. arctros Linn., part of the skull of a cave lion Felis spelaea Goldf., a fragment of the tarsal bone of a horse Equus caballus Linn., and a fragment of the antler of a giant deer Megaloceros sp. (identified by E. V. Alekseeva). In terms of aggregate composition, the rocks of the loess sequence belong to silty heavy, more rarely medium, loams; moreover, the loams of the lower bed of the section are more sandy (Fig. 1) and, accordingly, less silty.

In the mineralogical composition, the fine fraction predominates (98.01–99.01%), the principal minerals of which are quartz (48–50%, and in the buried soils, the upper and middle ones, 55%) and feldspars (22–43%). Micas (4–12%), rock fragments (3–12%), and, in one sample (from the base of the lower bed), calcite (4%) are present in small quantities. The heavy fraction is characterized by a high content of epidote (36–50%), magnetite (15–20%), and green hornblende (24–30%). Garnets (2–3%), zircon (2%), anatase (1–2%), leucoxene (1.0–1.5%), apatite (1–2%), tourmaline (1–2%), muscovite (1–3%), and sphene (0.5–1%) occur in smaller amounts. The clay minerals are represented by hydromica with an admixture of kaolinite; in the upper buried soil, by beidellitized hydromica.

The bulk chemical composition remains essentially the same as in the alluvial loams, but in the loess-like loams the amount of CaO increases—3.92–7.12%, while in the buried soils it decreases (1.74–3.65%).

Finds of large mammals of the Upper Paleolithic complex make it possible to date the enclosing loess rocks to the Late Pleistocene; the underlying terrace deposits may provisionally be dated to the Middle Pleistocene.

REFERENCES

1. A. M. Kuzmin. Materials for the subdivision of the glacial period in the Kuznetsk-Altai region. Izv. Zap. Sib. geol. kom., vol. VIII, issue 2, Tomsk, 1929.

2. Yu. B. Fainer. The history of the development of the Kuznetsk Basin in the Mesozoic and Cenozoic eras. Dissertation, Novosibirsk, 1967.

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

¹ A description of the woolly rhinoceros and other mammal finds will be published in the collection Problems of the Geography of Siberia, in the article by E. V. Alekseeva and E. D. Ryabchikova “On the question of the age of the loess rocks in the environs of the city of Novokuznetsk.”

² A description of the carnivores is given in the article by E. V. Alekseeva “Pleistocene Carnivores of Western Siberia,” Trudy ZIN, 1969.