NEW DATA ON THE STRUCTURE AND AGE OF THE TERMINAL PERMIAN STRATA IN THE SOUTH VERKHOYANSK REGION (northeastern Asia)
A.S. Biakov1,2, Yu.D. Zakharov3, M. Horacek4, S. Richoz5, R.V. Kutygin6, Yu.Yu. Ivanov1, E.V. Kolesov1, A.G. Konstantinov7,8, M.I. Tuchkova9, T.I. Mikhalitsyna1
1N.A. Shilo Northeast Interdisciplinary Scientific Research Institute, Far Eastern Branch, Russian Academy of Sciences, ul. Portovaya 16, Magadan, 685000, Russia
2Kazan Federal University, ul. Lenina 18, Kazan, 420008, Russia
3Far East Geological Institute, Far Eastern Branch, Russian Academy of Sciences, pr. Stoletiya Vladivostoka 159, Vladivostok, 690022, Russia
4BLT Wieselburg, HBLFA Francisco-Josephinum, Rottenhauserstrasse, 1, 3250 Wieselburg, Austria
5Karl-Franzens-Universität Graz, Heinrichstrasse, 26, Graz, 8010, Austria
6Diamond and Precious Metal Geology Institute, Siberian Branch, Russian Academy of Sciences, pr. Lenina 38, Yakutsk, 677891, Russia
7A.A. Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
8Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
9Geological Institute, Russian Academy of Sciences, Pyzhevskii per. 7, Moscow, 119017, Russia
Keywords: Biostratigraphy, bivalves, carbon isotopes, upper Permian, Permian-Triassic boundary, South Verkhoyansk region, northeastern Asia
Abstract
We present new data on the structure and age of the upper Permian strata in the basin of the Setorym River (tributary of the Vostochnaya Khandyga River) in the South Verkhoyansk region, represented by the Imtachan Formation and the lower part of the Nekuchan Formation. Based on the new findings of bivalve fossils from the Intomodesma costatum Zone, as well as on the study of carbon isotopes in the shells and carbon isotopes of the organic matter of the host mudstones, we have for the first time proved the completeness of the Permian section. The detailed description of the contact between the Imtachan and Nekuchan Formations bears evidence for a certain continuity of the lithologic characteristics of the sandstones. The sharp lithologic contact between the formations reflects not a regional sedimentation hiatus but a shift of depositional settings from the upper parts of a delta to the deep shelf, caused by forced marine transgression. It is concluded that there was no long-term hiatus between the accumulation of the Imtachan and Nekuchan Formations. Images of the most characteristic species of bivalves and crinoids from the Imtachan Formation are presented.
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