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.

中文翻译：

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Tunka凹陷东部更新世矿床年龄和形成条件的新证据

本文介绍了对位于伊尔库特河左岸（西斯贝卡利亚西南部通卡洼地）著名参考 Belyi Yar II 剖面砂岩底部的富含有机质沉积物的综合地质年代学研究结果。发现在1960年代，该剖面下部的一批湖沼沉积物归于上始更新世，上覆砂岩归于中更新世的萨马罗沃期。后来，根据最初的 14C 测年，对这些沉积物的地层进行了修订。沉积物的下部归因于 Karginsky 时代，而上覆的沙层归因于 Sartanian 冰川作用。然而，关于这些沉积物的成因、年龄和形成条件的问题仍然存在争议。特别是，14C 的各个日期相差很大；因此，他们需要进一步核实。对 Belyi Yar II 剖面下部的重新研究发现了冲积成因的泥炭和 gyttjas 矿床。结果表明，他们的数字年龄超出了 14C 测年方法的限制。古植物学资料表明，木桐形成于相对温暖湿润的气候条件下，上覆层在寒冷和更多的旱生条件下堆积。对这些有机成矿床的 230Th/U 等时年龄的评估，结合孢粉学数据，表明 Belyi Yar II 剖面的砂层底部不是在 Karginsky 时期（MIS 3）形成的，正如之前认为的那样，但是在 MIS 5 期间。gittya 可能在 MIS-5c 期间形成，而覆盖的泥炭层形成，