Quaternary depositional systems in northern Lake Baikal, Siberia

New high-resolution seismic reflection data from northern Lake Baikal and d etailed land-based morphological and sedimentological data reveal a variety of coarse-grained deposits in the northern Baikal Rift. Each depositional facies is assigned to a specific structural domain. Alluvial fans (onshore) and small fan deltas (offshore) dominate the western border-fault flank. G lacial deposits (onshore) and large glacio-lacustrine fans (offshore) chara cterize the eastern flexural margin. In the north, the axial rift terminati on comprises a large fluvial delta. This distinct pattern of depositional e nvironments reflects the pronounced asymmetry of the rift and emphasizes th e role of rift structure in controlling drainage and the location and type of rift-basin fill. Climate, however, exerts a profound influence on the ge neration and availability of coarse-grained material. This is best document ed along the eastern rift margin where Pleistocene valley glaciers advanced at >50, 40-35, and 26-13 ka from the high rift shoulders down to, and beyo nd, the present shore into the Baikal Basin. During these phases, large vol umes of glacial sediment were introduced into the basin, accumulating in ex tensive glacio-lacustrine outwash fans. About one-third of the seismically penetrated rift fill is glacial-outwash material derived from the eastern s houlder. Under present-day nonglacial conditions, however, the fans are ina ctive because of insufficient sediment supply; this documents the importanc e of major climatic fluctuations with respect to the magnitude of sediment discharge and accumulation. The sedimentary history also underscores the mo difying effects of climate-driven processes on the typical structure-domina ted aspects of rift sedimentation.