Evidence of Lowstand of Lake Baikal during the Last Glaciation

摘要

Reconstruction of paleolevels in Lake Baikal is important in the study of its paleoclimatic sedimentary record and interpretation of the history of its endemic fauna origin. This work presents evidence of lowstand of Lake Baikal (40-45 m lower than the present-day level) during the Last Glaciation. The record of uranium isotope distribution in Baikal sediments accumulated over the last 100 ka allowed us to suggest a model of humidity variation in East Siberia [1]. According to the model, precipitation in the Baikal drainage basin during maximal global glaciations was substantially lower compared to the present-day value and was compensated by evaporation in the plain area. As a result, the flow of the Selenga River, the main tributary of Lake Baikal, ceased and the lake became closed. However, it did not dry up, because moisture evaporated from its surface returned via glaciers formed in the surrounding mountains. Based on seismic profiling and study of the lithological composition of bottom sediments in the Selenga River prodelta (radiocarbon dating included), the authors of [2] identified horizons corresponding to a lowstand of Lake Baikal during the marine isotopic stage MIS 2 (18 ka ago, Last Glaciation Maximum). Reconstructed paleolevels differed in two studied areas of the Selenga prodelta. The reconstruction showed that the prodelta is located 45 m lower in the northwestern part and 33 m lower in the southwestern part as compared to the present-day water level. The difference was probably caused by postsedi-mentary movements. The purpose of this work was to seek new signs of lowstand in Lake Baikal during the Last Glaciation.