Climate Records From Surface Sediment Cores In Lake Yogo And Lakeonuma In Japan

Lake Yogo lies in Shiga in Japan, Lake Onuma is lacated in the southwestern in Hokkaido, many air currents join Lake Yogo and Lake Onuma area. It is a sensitive area to climate changes.We took4surface sediment cores in Lake Yogo and2surface sediment cores in Lake Omuna using a hand-held cylindrical gravity core sampler on March2011and July2011. We sub-sampled in the laboratory at0.5cm intervals or1cm intervals in the laboratory.In this paper, we will analysis water content, median grain size, organic content, biogenic silica content and particle density in the sediment cores from Lake Yogo and Lake Onuma, and try to interpretation hundreds years scale climate changes with137Cs and210Pb dating. We calculate mean sediment rate:YGS11-4is0.10g/cm2/y; YGS11-5is0.087g/cm2/y; ON11-4is0.0977g/cm2/y; and ON11-7is0.43g/cm2/y. Grain size from lake sediments could indicate the changing of precipitation in basins, organic matter and biogenic silica from lake sediments could indicate lake productivity and temperature variation.The results showed that median grain size (φ) in Lake Yogo was very about7.89(φ)-7.41(φ);organic matter content was between7.13%-23.21%. Median grain size (φ) in Lake Onuma was very about7.63(φ)-6.62(φ); organic matter content was between9.90%-18.59%.The results showed that there were3periods about climate changes more than900years in Lake Yogo:the first period:1088y-1350y, climate was warm and wet; the second period:1350y-1860y, climate was cooler and drier; the third period:1860y-2011y, climate was warm and dry.The results showed that there were3periods about climate changes recent200years in Lake Onuma:the first period:1832y-1900y, climate was warm and wet; the second period:1900y-1960y, climate was cooler and drier than the first period, but still warm and wet; the third period:1960y-2011y,climate was warm and dry. Some climate events had record in cores of Lake Yogo.