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Institut für Geowissenschaften, Universität Potsdam, PO Box 601553, 14415 Potsdam, Germany (e-mail: back{at}rz.uni-potsdam.de)
New morphological, sedimentological, and radiocarbon data of Quaternary deposits from the northern Baikal Rift document at least three extensive late Pleistocene glaciations at >50 ka, 40–35 ka, and 26–13 ka, respectively. During these periods valley glaciers advanced from the high rift shoulders (>2500 m) down to the present-day coast of Lake Baikal (456 m); in places, the glaciers advanced beyond the present-day shoreline into the lake basin as indicated by large moraines exposed in steep cliffs along the lakeshore. Furthermore, stratigraphic relations between lacustrine sequences and glacial deposits, as well as 14C-ages of two palaeo-shorelines 10 and 4 m above the present lake level, show that the last and the penultimate glaciations were followed by relative lake highstands. These land-based observations document a significant influence of late Pleistocene glaciations on the sedimentary development of this lacustrine rift basin.
The northern Baikal Rift is characterized by an asymmetric half-graben geometry that controls river drainage and sedimentation. This asymmetry greatly influenced the development and spatial distribution of Pleistocene glaciers on both rift margins. On the western flank, tilted fault blocks parallel to the rift served as topographic barriers for valley glaciers advancing toward the lake basin; only in two locations glaciers could reach the present-day coast. On the eastern rift flank, in contrast, structure and drainage conditions allowed the development of numerous consequent streams providing thoroughfares and space for recurrent valley glaciations. Thus, the glaciers on the eastern flank could advance beyond the present-day lakeshore into the lake basin in numerous locations. These observations indicate that asymmetric rift structure in combination with the effects of global cooling were the important controls on the Pleistocene glacial development of the Baikal Rift.
Keywords: Lake Baikal, Pleistocene, glaciation, sedimentation, half grabens.
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