Stratigraphy of multiple piston-core sediments for the last 30,000 years from Lake Biwa, Japan

Analysis of seven piston cores obtained from three sites in Lake Biwa provi de a detailed stratigraphy of the lake sediments for the last 30 kyrs. Desc ription of lithology and measurement of magnetic susceptibility reveal occu rrence of volcanic ashes at ten horizons, that were visually observed or mi croscopically found from clayey sediments. Most ash layers are observed in multiple cores from the three sites and also in earlier cores, establishing correlation and age assignment of the core sediments. This result demonstr ates usefulness of magnetic susceptibility data in finding dispersed volcan ic ashes. The age-depth curves deduced from published tephra ages show that significant difference in sedimentation rates occurs in Lake Biwa. The cen tral part of the depression is characterized by homogeneous sediments depos ited with a high sedimentation rate. The 250-m-thick lacustrine clay in thi s sub-basin has great potential for high-resolution study of the past envir onment and paleomagnetism for the last 0.5 Myr.