Sr isotopic ratios in core sediment of Lake Ogawara and paleo-salinity indicators

Abstract

We carried out the Sr isotope measurements of phases that could be a paleo-salinity proxy, extracted from varve sediment samples in 20-m-long boring core at the center part of Ogawara lake located in the Aomori east shore in the autumn of 2009. The objective is to examine the possibility of reconstruction of paleo-salinity change of lake-water in present brackish lake. If the paleo-salinity change during the late thousands of years could be restored from a varved-lacustrine-sediment core, we will be able to investigate the tsunami attack history with a highly precise time-axis and also the sea-level change during the time. From our preliminary result, it seems that change of Sr isotopic ratio in a carbonate phase" very often synchronizes with the change of the depositional environment described stratigraphically in the columnar section. "