MULTIWAVE XRF-SR DETERMINATION OF U AND TH IN BOTTOM SEDIMENTS OF LAKE BAIKAL: BRUNHES PALEOCLIMATIC CHRONOLOGY

Abstract

The paper presents a new method of U and Th determination in bottom sediments implying synchrotron radiation with monochromatic beams at different energies, registration, and iterative joint processing of the resultant XRF (X-ray fluorescent) spectra series. The validity of the new method was proved by comparison of U and Th determinations by XRF-SR in different sediment samples with earlier INAA and ICP-MS results for the same samples. Profiles of U and Th were measured at the sampling rate of 2 ka in a drilling core (BDP-96-2) of bottom sediments from Lake Baikal deposited 40 to 780 ka BP. Oscillations of U contents and U/Th ratios record global climate change throughout the Brunhes epoch (780 ka BP), and the response of these "warm" proxies is similar to that observed earlier in shorter cores spanning the last two interglacials (220-0 ka BP).