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

The mineral assemblage of Pliocene-Pleistocene bottom sediments of Lake Bai kal, exposed by the deep-sea BDP-96-2 (Baikal Drilling Project) has been st udied by the methods of XRD and IR spectroscopy. Complex XRD patterns of cl ay minerals have been modeled using an advanced algorithm based on calculat ion of interference function from one-dimensional disordered crystals of fi nite thickness. The modeling implies fitting of theoretical to observed pat terns and optimization procedure by methods of nonlinear programming. It ha s been shown that major day minerals in the sediments that formed for the p ast 2.5 Ma during cold stages are illite-illite-smectites with predominantl y illite Layers, and chlorite; the principal clay minerals in the sediments that formed during warm periods are smectite, illite-smectites with high c ontents of smectite layers, and chlorite-smectites. These data allow unrave lling the climate history of Lake Baikal from biogenic silica record.