TY - JOUR

T1 - New Evidence on the Age and Formation Conditions of Pleistocene Deposits in the Eastern Part of the Tunka Depression

AU - Maksimov, F.E.

AU - Savelyeva, L. A.

AU - Laukhin, S. A.

AU - Petrov, A. Yu.

AU - Popova, S. S.

AU - Larin , S. I.

AU - Kobylkin, D. V.

AU - Kuznetsov, V. Yu.

AU - Grigoryev , V. A.

AU - Levchenko, S. B.

AU - Yakimova, K. S.

N1 - Publisher Copyright: © 2020, Pleiades Publishing, Ltd. Copyright: Copyright 2020 Elsevier B.V., All rights reserved.

PY - 2020/12/8

Y1 - 2020/12/8

N2 - Abstract: This article presents the results of a comprehensive geochronological study of organic-rich sediments lying at the base of the sand suite in the well-known reference Belyi Yar II section on the left bank of the Irkut river (Tunka depression, Southwestern Cisbaikalia). It was found that in the 1960s, a pack of lake-marsh sediments from the lower part of the section was assigned to the upper Eopleistocene, and the overlying sands to the Samarovo period of the Middle Pleistocene. Later, based on the first 14C datings, the stratigraphy of these sediments was revised. The lower part of the sediments was attributed to the Karginsky time, and the overlying sands to the Sartanian glaciation. However, the questions concerning the genesis, age and conditions of formation of these sediments remain controversial. In particular, the individual dates of 14C differ greatly from one another; therefore, they require further verification. A renewed study of the lower part of the Belyi Yar II section discovered peat and gyttjas deposits of alluvial origin. It was shown that their numerical age is beyond the 14C dating method limits. Paleobotanical data showed that the gittya was formed in conditions of a relatively warm and humid climate, and the overlying layers accumulated in the cooling and more xerophytic condition. Evaluation of the 230Th/U isochronous age of these organogenic deposits, combined with palynological data, suggested that the bottom of the sand layer in the Belyi Yar II section was not formed during the Karginsky time (MIS 3), as was thought previously, but during MIS 5. The gittya could have formed during MIS-5c, whereas the overlying peat layers formed, possibly, at the transition to MIS-5b.

AB - Abstract: This article presents the results of a comprehensive geochronological study of organic-rich sediments lying at the base of the sand suite in the well-known reference Belyi Yar II section on the left bank of the Irkut river (Tunka depression, Southwestern Cisbaikalia). It was found that in the 1960s, a pack of lake-marsh sediments from the lower part of the section was assigned to the upper Eopleistocene, and the overlying sands to the Samarovo period of the Middle Pleistocene. Later, based on the first 14C datings, the stratigraphy of these sediments was revised. The lower part of the sediments was attributed to the Karginsky time, and the overlying sands to the Sartanian glaciation. However, the questions concerning the genesis, age and conditions of formation of these sediments remain controversial. In particular, the individual dates of 14C differ greatly from one another; therefore, they require further verification. A renewed study of the lower part of the Belyi Yar II section discovered peat and gyttjas deposits of alluvial origin. It was shown that their numerical age is beyond the 14C dating method limits. Paleobotanical data showed that the gittya was formed in conditions of a relatively warm and humid climate, and the overlying layers accumulated in the cooling and more xerophytic condition. Evaluation of the 230Th/U isochronous age of these organogenic deposits, combined with palynological data, suggested that the bottom of the sand layer in the Belyi Yar II section was not formed during the Karginsky time (MIS 3), as was thought previously, but during MIS 5. The gittya could have formed during MIS-5c, whereas the overlying peat layers formed, possibly, at the transition to MIS-5b.

KW - Quaternary deposits

KW - depression of the Baikal type

KW - geochronology

KW - paleobotanical method

KW - radiocarbon method

KW - uranium-thorium method

UR - http://www.scopus.com/inward/record.url?scp=85097278382&partnerID=8YFLogxK

U2 - 10.1134/S1875372841030087

DO - 10.1134/S1875372841030087

M3 - Article

VL - 41

SP - 266

EP - 277

JO - Geography and Natural Resources

JF - Geography and Natural Resources

SN - 1875-3728

IS - 3

ER -