10 Be record and magnetostratigraphy of a Miocene section from Lake Baikal: Re-examination of the age model and its implication for climatic changes in continental Asia

Abstract

We determined the concentration of the cosmogenic radionuclide 10Be in the Miocene section of a sediment core (5-12 My BP) retrieved from Lake Baikal (BDP98-hole2) that had been previously dated by the magneto-stratigraphic (MS) method. Using our new 10Be geochronology we reexamined the MS age-depth assignments and found inconsistencies. We therefore reexamined the MS record and propose a new model which is consistent with the 10Be data, with an age of 8.4 My BP at a depth of 600 meters. Accepting the revised MS ages, we found the profile of the decay-corrected 10Be concentration, which shows ca. 50% decreases of 10Be during the periods 0-2.7 My BP and 5.3-5.8 My BP. We also detected considerable increases of the 10Be flux into sediments before 4.5 My BP.