Climatic and vegetation changes in the Baikal region for the last 5 Ma (according to palynological data on the Baikal sediments)

A palynological analysis of the Baikal sediments from a 200 m deep borehole permitted tracing continuous climatic and vegetation changes in the Baikal region for the last 5 Ma (from the Early Pliocene). The sediment age was d etermined by paleomagnetic analysis, correlation of the obtained palynologi cal data with the available material on this region and the adjacent areas, and extrapolation of sedimentation rate data. The complex of the obtained data evidences a relatively even sedimentation in the above period. The veg etation changes were caused mainly by the gradually progressing cooling of climate in the Tertiary and its strong fluctuations in the Quaternary. It h as been established that there were at least three coolings, recurrent appr oximately every million years: 2.6-2.8, 1.6-1.8, and about 0.6 Ma BP. The c hange of landscapes proceeded regularly. First forest and forest-steppe sma ll-leaved and conifer-broad-leaved landscapes gave way to forest dark-conif erous (spruce or cedar) ones, which, in turn, were replaced by forest light -coniferous (larch) and forest-tundra landscapes. When the cold periods end ed, the regional vegetation again restored its initial, primarily forest, h abit but, at the same time, became compositionally poorer because of the ex tinction of certain plant species.