Clay minerals in bottom sediments of Lake Baikal as indicators of climate change

The mineral assemblage of Pliocene-Pleistocene bottom sediments of Lake Baikal, exposed by the deep-sea BDP-96-2 (Baikal Drilling Project) has been studied by the methods of XRD and IR spectroscopy. Complex XRD patterns of clay minerals have been modeled using an advanced algorithm based on calculation of interference function from one-dimensional disordered crystals of finite thickness. The modeling implies fitting of theoretical to observed patterns and optimization procedure by methods of nonlinear programming. It has been shown that major day minerals in the sediments that formed for the past 2.5 Ma during cold stages are illite-illite-smectites with predominantly illite Layers, and chlorite; the principal clay minerals in the sediments that formed during warm periods are smectite, illite-smectites with high contents of smectite layers, and chlorite-smectites. These data allow unravelling the climate history of Lake Baikal from biogenic silica record.