Detailed diatom biostratigraphy of Baikal sediments during the Brunhes Chron and climatic factors of species formation

The Baikal bottom sediments (borehole BDP-96-2) are stratigraphically chara cterized in detail (with a 500 year resolution) within the Brunhes Chron. T he sediment section 35 m thick shows a distribution of diatoms (25 species and varieties), sponge spicules, and golden-algae cysts. Thirty-one local d iatom zones are recognized in the section, providing a derailed stratigraph ic division of the Baikal sediments. The distribution of diatom frustules a nd the diatom zones are correlated with the marine isotope stratigraphy. Cl imate played an important role in the formation of species of plankton diat oms in the lake. More than 21 new species of diatoms appear and then disapp ear in the section. Diatom species extinguished when glaciations began, and new species appeared during interglaciations. This suggests that the evolu tion of plankton diatoms in Baikal is under climatic control.