AN ATTEMPT TO ESTIMATE THE SURFACE-TEMPERATURE OF THE JAPAN SEA IN THE EARLY PLEISTOCENE BY USING A MOLLUSCAN ASSEMBLAGE

In order to estimate the surface temperature of the Japan Sea in the E arly Pleistocene, the shallow water molluscan assemblage (Mizuhopecten -Glycymeris assemblage) of the Omma-Manganji fauna was examined by usi ng the HDM characteristic curve (Ida, 1956) and climato-geographic zon ing methods. Consequently, the average ocean temperatures of the Japan Sea borderland in Early Pleistocene were estimated to be 0.5-3.0-degr ees-C lower than the Recent ones. During this time, intermittent invas ions of warm current into the Japan Sea frequently took place with the opening of the paleo-Tsushima Strait. However, the obtained data in t his study show that the Early Pleistocene climate of Japan Sea was les s strongly affected by the warm current than the Recent one.