Abstract:
The particle density of BDP 98 core sediments (total length 674 m) drilled in Lake Baikal in 1998 is controlled by their diatom valve contents. Deposition of abundant diatom valves occurs during warm periods, and clay particles with few diatom valves deposit during cold periods. Paleoclimates around Lake Baikal are reconstructed based on these facts. Climatic history recorded in the BDP 98 core during the last 6.5 Ma can be roughly classified into three phases based on the variation of particle density: Phase 3 (6.5-3.2 Ma) of constant lower density, Phase 2 (3.2-1.8 Ma) of abrupt shift to higher density, and Phase 1 (1.8 Ma-to present) of high amplitude density changes with overall higher density. Climatic changes shown in the particle density profile of Phases 3 to 1 show a rough similarity with the delta (super 18) O record of benthic foraminifers of marine sediment cores. Particle density of the BDP98 core of Quaternary, Phase 1, also has good similarity with the delta (super 18) O record in a scale of tens of thousands years. Therefore, sediment ages and sedimentation rates of this period can be estimated by comparing the particle density profile of the BDP 98 core with the oxygen isotope ratio curve. Further, the biogenic silica content in sediments can also be estimated by particle density of the BDP 98 core postulating some other factors. Diatom production (biogenic silica flux), calculated from both biogenic silica content in sediments and sedimentation rate, fluctuates periodically in concordance with the delta (super 18) O record. These results also reveal some local characteristics of the Lake Baikal region such as cold periods of 1.77-1.45 Ma and 0.9-0.8 Ma, distinct cold events in interglacial periods since MIS 9, and the presence of a clear 100-kyr-frequency since 1.5 Ma.