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

Abstract

A 150 ky record of 10Be found in the sediments of Lake Baikal is compared with the two geochemical stacks indicating warm and cold climates (“warm stack” and “cold stack”). The stacks were calculated from the concentrations of elements which were determined by Synchrotron Radiation X-Ray Fluorescent Analysis and Neutron Activation Analysis. The profiles of 10Be concentrations and flux suggest that the main reason of the fluctuations was the changing extents of dilution with terrigenous matter and diatom algae in layers belonging to warm and cold periods marked by the peaks of geochemical stacks. Contrary to the explanations proposed for other records, the rate of production of cosmogenic 10Be is not the principal reason of 10Be fluctuations in the sediments of Lake Baikal; however, the minor peak of 10Be flux at ca. 40 ky BP may be partly due to the global increase in the production of 10Be around the Laschamp excursion. The concentrations of 10Be in the terrigenous fraction, as well as values of the warm geochemical stack, abruptly decreased at the wake of the cold stages, suggesting an increased rate of production of clastic matter which was the source of the terrigenous fraction of the lake sediments. Hence, they are candidates for the proxy of the accumulation rate of terrigenous materials in Lake Baikal sediments.