First study of fossil diatom flora from Middle Miocene-Lower Pliocene lacustrine sediments in BarguzinValley, Baikal Rift Zone

A subsequent formation of oligotrophic tectonic paleo-lakes Bodon-1 and Bodon-2 is reconstructed through study of fossil diatom flora in sediments of the upper stratum of the Tankhoy Formation in the south of Barguzin Valley. The first lake is characterized by the development of Middle - Late Miocene planktonic species-Aulacoseira sp. 1 and 2 (diatom zones 1 and 2), then - of the species Pseudoaulacoseira moisseeviae (diatom zone 3). The second lake is identified due to Early Pliocene species A. islandica, A. canadensis and Eunotia poly-glyphoides (diatom zone 4). The diatom flora of zone 3 of paleo-lake Bodon-1 is correlated to similar zone in paleo-lakes in Vitim Plateau. It was assumed, that these lakes were formed simultaneously with the paleo-lake Mukhal on the Vitim plateau (ca. 13-12 million years ago) and the paleo-lake Yuzhnoe (ca. 10-9 million years ago and later).