A new record of Holocene climate change from the bottom sediments of Lake Baikal

Detailed siliceous microfossil records (diatoms and chrysophyte cysts) from the BDP-93-2 borehole with resolution of ca 30-120 years were obtained fro m Lake Baikal sediments to test the sensitivity of the Lake Baikal system t o minor climate changes during the Holocene. Our new results demonstrate th at the Subboreal period is characterized by the highest accumulations of di atom frustules and chrysophyte cysts in Lake Baikal sediments. The siliceou s microfossil record suggests that the Holocene climatic optimum in this in terior part of Asia corresponds to the Subboreal period 2.5-4.5 ka and not to the Atlantic period 4.6-6 ka. Although quite different from Holocene rec onstructions for the European part of Eurasia, the Holocene sedimentary rec ord from Lake Baikal shows good correlation with palynological and soil cli matic records from southeast Siberia and Mongolia where similar responses o f the terrestrial biosphere are also documented, A distinctive monospecific lamina of Synedra acus diatom species, coincident with the maximum of chry sophyte cyst accumulation during the Subboreal period, argues for the possi ble short-term changes of the trophic state of Lake Baikal from oligotrophi c, with a cold-water diatom assemblage, to eutrophic with a thermophilic mo nospecific diatom flora. Comparison of diatom and cyst responses provides a key to distinguishing the humidity from temperature response in future stu dies of high-resolution records of Lake Baikal. (C) 2000 Elsevier Science B .V. All rights reserved.