Miocene stratigraphy and spore-pollen complexes of the Tyulgan brown coal mine (Southern Urals)

R.G. Kurmanov

Institute of Geology, Ufimian Scientific Centre, Russian Academy of Sciences, Ufa, 450077 Russia

E-mail: ravil_kurmanov@mail.ru

Received June 14, 2017

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Abstract

The results of the palynological investigations of the Miocene sediments of the Tyulgan brown coal mine are summarized and discussed in this paper. Seven pollen complexes have been established according to the pollen analysis of the Tyulgan, Kuyurgaza, and Voroshilovka horizons (Cis-Uralian Superhorizon, Lower-Middle Miocene). The less informative pollen complexes have been discovered from the deposits of the Ushkatly horizon (Middle-Upper Miocene). Six sections of the Tyulgan brown coal mine have been stratified and correlated on the basis of the palynological data. New data on the vegetation evolution, main sources of coal, sedimentation, and climate changes of the Southern Urals during the Miocene have been obtained. It has been revealed that the Tyulgan time was characterized by the warmest (subtropical) climate when Taxodiaceae forests developed. During the Kuyurgaza time, the climate changed from cool to warm and back to cool at the end. The Voroshilovka time is characterized by warm climate conditions. In summary, vegetation of the studied area during the Miocene changed in the following way: 1) coniferous-broadleaved forest with significant participation of the subtropical elements; 2) mixed broadleaved forests, 3) coniferous forests with admixture of small- and broadleaved trees, 4) small-leaved forests and mixed small- and broadleaved forests with admixture of the subtropical elements. Two types of sediment accumulation conditions have been established – low swamps developed during the Tyulgan and Kuyurgaza time and transitional swamps that existed during the Voroshilovka time. According to the palynological analysis, Taxodiaceae, Nyssa sp., Alnus sp., Sphagnum sp., and Polypodiaceae were the main coal-forming plants.

Keywords: palynology, Miocene, Tyulgan, Kuyurgaza, Voroshilovka, Ushkatly horizons, South Urals brown coal basin

Acknowledgments. I would like to thank Natal'ya Yur'evna Fillipova, a senior research fellow of the Paleofloristic Laboratory, Geological Institute, Russian Academy of Sciences (Moscow), Candidate of Geological and Mineralogical Sciences, for her valuable critical remarks and comments on the manus­cript.

Figure Captions

Fig. 1. The geological map (A) and section (B) of the Tyulgan brown coal mine [1]. The lithological and structural des­cription: 1 – red sediments (limestones, argillite-like clays, sands, sandstones, and conglomerates); 2 – red sediments (sandstones with clay and argillaceous interlayers, conglomerates); 3 – Triassic multicolored sediments; 4 – gray and multicolored argillaceous aleurites, aleuritic clays, rare sands and pebble gravel sediments, brown coal interlayers; 5 – white quartz sands and aleurites with micaceous clay and coal lenses in the upper part and gravel sediments at the bottom; 6 – gray clays and brown coal deposit, at the fringe zone – sandy clays and argillaceous sands; 7 – gray clays, brown coals, sandy clays and argillaceous sands with pebbles; 8 – gray and multicolored sandy clays and argillaceous sands, pebble gravel at the bottom; 9 – Pliocene pebble gravel sediments, sands, and clays; 10 – Quarternary continental sediments; 11 – brown coal; 12 – argillaceous coal; 13 – carbonaceous clay; 14 – clay with lignite fragments; 15 – clay; 16 – gypsum; 17 – sandy clay; 18 – sand; 19 – sand with pebbles; 20 – pebble gravel; 21 – clay loam; 22 – burning rocks; 23 – fault; 24 – fault zone on the surface or under Quaternary sediments (in plan); 25 – outlines of the coal deposit. The indices of stratigraphic units: 26 – Tartarian Stage of the Upper Permian; 27 – Kazanskian Stage of the Middle Permian; 28 – Kaltaevskian and Surakaiskian Formations of the Middle-Upper Triassic; 29 – Upper  Triassic-Lower Jurassic, unstratified; 30 – Tyulganskian Formation of the Lower Miocene; 31 – Kuyurgazinskian Formation of the Lower Miocene; 32 – Ushkatlinskian Formation of the Middle-Upper Miocene; 33 –Voroshilovskian and Ushkatlinskian Formations (unstratified) of the Miocene; 34 – Pliocene; 35 – Quaternary, 36 – section site.

Fig. 2. Pollen from the Lower Miocene sediments of the Tyulgan brown coal mine: 1 – Taxodium sp., sample no. 4, section 1; 2 – Glyptostrobus sp., sample no. 4, section 1; 3 – Corylus sp., sample no. 23, section 2; 4 – Quercus sp., sample no. 23, section 2; 5, 6 – Castanea sp., sample no. 56, section 3; 7 – Alnus sp., sample no. 95, section 4; 8, 9 – Nyssa sp., sample no. 4, section 1; 10 – Pinus s/g Haploxylon, sample no. 4, section 1; 11 – Pinus s/g Diploxylon, sample no. 90, section 4.

Fig. 3. Spore-pollen diagram and lithological des­cription of the Lower Miocene deposits at the Tyulgan brown coal mine. Section 1. Lower bench of the eastern initial cut. In Figs. 3–9: 1 – tree-shrub pollen, 2 – herb-dwarf shrub pollen, 3 – spores, 4 – clay, 5 – ferritization, 6 – brown coal, 7 – pebbles, 8 – sand, 9 – clay loam, 10 – break. Genetic indices: b – biogenic, l – lacustrine, a – alluvial. Abbreviated plant names: Cupr. – Cupressaceae, Engel. – Engelhardia sp., Eph. – Ephedra sp., Eq. – Equisetum sp., Er. – Ericaceae, Frax. – Fraxinus sp., Gl. – Glyptostrobus sp., Ketel. – Keteleeria sp., L. – Lycopodium sp., Liq. – Liquidambar sp., Lon. – Lonicera sp., Myrt. – Myrtaceae, Oph. – Ophyoglossaceae, Pinus D/x – Pinus s/g Diploxylon, Podoc. – Podocarpus sp., Zelk. – Zelkova sp.

Fig. 4. Spore-pollen diagram and lithological des­cription of the Lower Miocene deposits at the Tyulgan brown coal mine. Section 2. Lower bench I near the southern pumping station.

Fig. 5. Spore-pollen diagram and lithological des­cription of the Lower Miocene deposits at the Tyulgan brown coal mine. Section 3. Bench II.

Fig. 6. Spore-pollen diagram and lithological des­cription of the Lower Miocene deposits at the Tyulgan brown coal mine. Section 4. Bench III.

Fig. 7. Spore-pollen diagram and lithological des­cription of the Lower Miocene deposits at the Tyulgan brown coal mine. Section 5. Bench IV.

Fig. 8. Spore-pollen diagram and lithological des­cription of the Lower Miocene deposits at the Tyulgan brown coal mine. Section 6. Bench V.

Fig. 9. Correlation of the studied geological sections based on the palynological data. The Roman numbers indicate palynocomlexes.

Fig. 10. The dynamics of vegetation and climatic conditions during the Miocene time at the Tyulgan brown coal mine: 1 – pine-spruce forests, 2 – mixed small- and broadleaved forests, 3 – coniferous-broadleaved and broadleaved forests (also taxodium ones).

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For citation: Kurmanov R.G. Miocene stratigraphy and spore-pollen complexes of the Tyulgan brown coal mine (Southern Urals). Uchenye Zapiski Kazanskogo Universiteta. Seriya Estestvennye Nauki, 2017, vol. 159, no. 4, pp. 629–653. (In Russian)

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