Climatic change record of the sediments in Lake Biwa,Japan during the last 1 Ma

Lake Biwa is the largest and oldest lake in Japan.The drilled core in 1982-1983（1400 m core） has revealed;00 m lake and terrestrial sediments overlying the basement rock.The age data obtained from fission-track dating and tephra correlation indicated the discontinuity of the sedimentary sequence in present Lake Biwa.Recendy,the doubt on discontinuity of the sequence in present Lake Biwa was completely cleared by the reinvestigation of the fission-track ages and tephra identification of Danhara et al（2010）.Improvements on fission track timescale have successfully identified the paleomagnetic data from middle Matuyama reversed Epoch including the Jaramillo event,determining time coverage of the Lake Biwa sediment as-1.5 Ma.A highly linear sediment accumulation rate curve is thus given to the 900 m deep Lake Biwa sediment.This secures the stable sedimentary environment of the basin,and the significance of Lake Biwa sediment as a good record for paleoclimate changes.Lake Biwa is,therefore,an ideal terrestrial site to explore paleoclimate and tectonic history during the past 1 Ma of East Asia.