Climate-induced variations of cosmogenic beryllium-10 in the sediments of Lake Baikal of the last 150 ky from AMS, SRXRF and NAA data

A 150 ky record of Be-10 found in the sediments of Lake Baikal is compared with the two geochemical stacks indicating warm and cold climates ("warm st ack" and "cold stack"). The stacks were Calculated from the concentrations of elements which were determined by Synchrotron Radiation X-Ray Fluorescen t Analysis and Neutron Activation Analysis. The profiles of Be-10 concentra tions and flux suggest that the main reason or the fluctuations was the cha nging extents of dilution with terrigenous matter and diatom algae in layer s belonging to warm and cold periods marked by the peaks of geochemical sta cks. Contrary to the explanations proposed for other records, the rate of p roduction of cosmogenic Be-10 is not the principal reason of Be-10 fluctuat ions in the sediments of Lake Baikal, however, the minor peak of Be-10 flux at ca. 40 ky BP may be partly due to the global increase in the production of Be-10 around the Laschamp excursion. The concentrations of Be-10 in the terrigenous fraction, as well as values of the warm geochemical stack, abr uptly decreased at the wake of the cold stages, suggesting an increased rat e of production of clastic matter which was the source of the terrigenous f raction of the lake sediments, Hence, they are candidates for the proxy of the accumulation rate of terrigenous materials in Lake Baikal sediments. (C ) 2001 Elsevier Science B.V. All rights reserved.