Molluscan fossils from core samples collected from off Joetsu during MD179 cruise

Abstract

Eleven molluscan species were recovered from 11 cores collected from off Joetsu during MD179 cruise of R/V Marion Defresne. They include three thyasirid species Conchocele bisecta, Thyasira tokunagai and T. sp. which are characteristic species of chemosynthetic fauna. The occurrence of these species corresponds to the horizon below and above the LGM (Last Glacial Muximum), suggesting that the seepage of fluid including methane not at the coldest time. From the bed corresponding to the LGM, many mollusks including two deposit feeders as Robaia robai and Yoldiella philippiana are concentrated probably because of rich organic matter during the LGM. This is also another criterion which the endemic species of the Japan Sea, Robaia robai could survive the deteriorated environment in deep-sea during the ice age.