LAST DEGLACIATION-HOLOCENE HIGH-RESOLUTION RECORDS FROM LAKE BAIKAL: EVIDENCES OF DRAMATIC ENVIRONMENTAL CHANGES IN SIBERIA

The many records from Siberia exhibit a linkage with climate of the North Atlantic. However, the environmental/climatic changes that are recorded in Siberia are not always similar and not absolutely synchronize with those observed in the North Atlantic region. These differences possibly represent the inner continental response of Asia to climatic changes influenced by changes of thermohaline circulation in the North Atlantic.

The high-resolution sedimentary records of Lake Baikal reveal new details about the response of the lake’s watershed and lacustrine ecosystem to climatic changes during LGM-Holocene transition. The last deglaciation of Baikal is characterized by an in increase in diatom productivity from almost zero during LGM to high levels during the Holocene. The first significant increase in diatom productivity in Lake Baikal occurred at ca. 13 Ka BP (¹⁴C age) during the Bflling-Allerfd warming. Diatom abundance and biogenic silica contents increased abruptly in approximately 300 years to reach the Holocene levels. However, the diatom assemblages were different and less diverse as compared with the Holocene.

This diatom bloom was abruptly interrupted about 11.5 Ka ago (¹⁴C age) with the beginning of the Younger Dryas (YD). As result diatom productivity drastically reduced to almost LGM levels. From this time forward glacial clay with ice rafted detritus (similar to LGM time) began to accumulate again in Baikal. These data indicate mountain glacial advanced in the lake watershed during the YD. However, the Baikal diatom productivity did not rebound with the end of YD 10 Ka BP, but instead remained depressed until end of Boreal time ca. 8 Ka BP (¹⁴C age). The total duration of the diatom productivity depression in Baikal exceeds 3 Ka. Many Siberian paleoclimate records also exhibit a deep cooling episode during Boreal time around 9-8 Ka (¹⁴C age) (Khotinsky, 1984; Volkova, 1989) suggesting that cooling during Boreal time was not restricted just to Lake Baikal area but was more widespread in Siberia.