ASYMMETRIC LATE PLEISTOCENE GLACIATIONS IN THE NORTH BASIN OF THE BAIKAL RIFT, RUSSIA

New morphological, sedimentological, and radiocarbon data of Quaternar y deposits from the northern Baikal Rift document at least three exten sive late Pleistocene glaciations at >50 ka, 40-35 ka, and 26-13 ka, r espectively. During these periods valley glaciers advanced from the hi gh rift shoulders (>2500 m) down to the present-day coast of Lake Baik al (456 m); in places, the glaciers advanced beyond the present-day sh oreline 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 C-14-ag es of two palaeo-shorelines 10 and 4 m above the present lake level, s how that the last and the penultimate glaciations were followed by rel ative lake highstands. These land-based observations document a signif icant influence of late Pleistocene glaciations on the sedimentary dev elopment of this lacustrine rift basin. The northern Baikal Rift is ch aracterized by an asymmetric half-graben geometry that controls river drainage and sedimentation. This asymmetry greatly influenced the deve lopment and spatial distribution of Pleistocene glaciers on both rift margins. On the western flank, tilted fault blocks parallel to the rif t 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 drai nage conditions allowed the development of numerous consequent streams providing thoroughfares and space for recurrent valley glaciations. T hus, the glaciers on the eastern flank could advance beyond the presen t-day lakeshore into the lake basin in numerous locations. These obser vations indicate that asymmetric rift structure in combination with th e effects of global cooling were the important controls on the Pleisto cene glacial development of the Baikal Rift.