Paleoenvironmental Changes during the Last 12 Million Years in the Eurasian Continental Interior Estimated by Chemical Elements in Sediment Cores (BDP-96 and BDP-98) from Lake Baikal

Abstract

The content of 29 chemical elements (Na, K, Mg, Ca, Al, Fe, Li, Be, Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Ga, Ge, As, Rb, Sr, Mo, Cs, Ba, W, Pb, Th, and U) in 589 subsamples of BD-P96 cores and 703 subsamples of BDP-98 cores from the Academician Ridge of Lake Baikal were determined using inductively coupled plasma-mass spectromety (ICP-MS) in order to estimate paleoenvironmental changes during the last 12 million years in the Eurasian continental interior. The content of terrigenous elements (Na, K, Mg, Ca, Al, Ti, etc.) increased gradually from about 6 Ma BP to the present, with repeated major fluctuations after 3.6 Ma BP, indicating a significant climate change at 3.6Ma BP in the Eurasian continental interior. The abrupt change may be mainly associated with the uplift of the Tibetan plateau and Himalayas. This result corresponds with the rapid increase in the eolian dust accumulation rate in the central north Pacific sediment core (Rea et al. 1998). The data from BDP98 cores indicated that some big changes in the sources of chemical elements occurred at about 7 Ma BP, when the sedimentation rate in the core suddenly increased. We also estimated from the chemical index of alteration (CIA) that the variation in the climate from 8 to 12 Ma BP was small, and the rapid climate change started at 3.6 Ma BP.