Late Pliocene Spongial Fauna in Lake Baikal (from Material from the Deep Drilling Core BDP-96-1)

Spicule analyses of part of the core from the BDP-96-1 bore hole corresponding to the late Pliocene were performed. The samples were dated by paleomagnetic analysis. An analysis of species composition allowed us to describe 40 sponge species, 14 of which belong to present-day Baikal sponges, while the other 26 species do not currently exist in Lake Baikal. According to the quantitative parameters of sponge spicules and species content, sponge fauna evolution in the late Pliocene was divided into three stages: (1) 3.1−2.9 Ma, corresponding to warm-water conditions; (2) 2.9-2.5 Ma, when the warm-water fossil species disappear, suggesting a sharp cooling down; (3) 2.5−2.1 Ma, when the sponge fauna was restored, but did not reach the full diversity of the first period. The dates obtained for sponges correspond well to palynological and diatom analyses of this core.