Geochemical signals of orbital forcing in the records of paleoclimates found in the sediments of Lake Baikal

X-ray fluorescent analysis with synchrotron radiation (SRXFA) and neutron activation analysis (NAA) were used to study the distribution of elements in sediments of Lake Baikal over the time interval of Brunhes Epoch (0-780 kyr BP). The concentrations of some elements and their ratio respond to changes of the climate. Sr/Ba, Sr/Rb, Sr/Cs, Sr/Fe, Sr/Ti, U/Th, Zn/Nb, Mo, Eu, Y, Yb positively correlate with the content of biogenic silica (BiSi) which is high at intervals belonging to interglacials and small at those belonging to glacials. On the contrary Ba, Rb, Cs, Th, La, Ce, Nd, La (Ce)/Yb (Y, Zr) negatively correlate with BiSi. These two series of geochemical signals, along with BiSi, reflect oscillations of the climate between glacials and interglacials. Spectral analysis of the records revealed that they are modulated by orbital forcing. This proves that the climates of East Siberia depend on orbital forcing to the similar extent, as does the global climate. Comparison of the climate records found in the sediments of Lake Baikal with the pattern of orbital parameters made it possible to estimate the mean rates of sediment accumulation over different time intervals and to refine the age-depth model. (C) 2000 Elsevier Science B.V. All rights reserved.