An environmental magnetic study of the sediments of Lake Baikal, Russia

The environmental magnetic approach was used to study sediment cores from Lake Baikal, south central Siberia, Russia. Rock-magnetic measurements show that variations in magnetic concentration and mineralogy of Lake Baikal sediment have a high correlation with the SPECMAP marine oxygen-isotope record indicating that Lake Baikal sediment preserves a history of climate change in central Asia for the last 250 kyr. This correlation provides a method of dating the sediment beyond the range of radiocarbon dating.; Paleomagnetic secular variation and relative paleointensity records from Selenga Prodelta cores accurately record variations in the geomagnetic field for the last 84 kyr. The secular variation record will be useful for future regional correlations. The Lake Baikal relative geomagnetic intensity record is highly correlated to marine intensity records dated by astronomically calibrated oxygen-isotope stratigraphy. Geomagnetic intensity stratigraphy provides a means of global correlation and dating for Lake Baikal sediments.; The origin of the Lake Baikal sedimentary magnetic record was investigated through detailed analyses of magnetic extracts. This study provides independent support for the interpretation of the rock-magnetic parameters. Single-domain magnetite found in the surficial sediments throughout Lake Baikal is inferred to be produced by magnetotactic bacteria. Post-depositional reduction diagenesis results in the loss of the fine-grained magnetosomes at depth. This study also reveals that fine-grained magnetite undergoes oxidation to a high-coercivity mineral during long periods of storage. Although the Lake Baikal sedimentary magnetic record has several complex components, by determining their origin this study has shown that the sediments are well-suited for environmental magnetic study.; In order to obtain long sediment records of paleolimnologic and climatic change, two holes were drilled to 100 m depth on the Selenga Prodelta. Magnetic susceptibility provides accurate core correlation. A coarse-resolution study indicates that the sediment is entirely Brunhes in age. In the upper 40 m, rock-magnetic parameters appear related to climate change with well defined glacial and interglacial rock-magnetic assemblages. Below 40 meters, the change in magnetic mineral assemblage suggests a change at the site to an environment dominated by fluvial inputs.