A Study of Quaternary Paleoenvironments and Paleobiology in Japan.

Abstract

This article presents that our investigations based on Paleobiology have good progress in understanding how environmental conditions changed and fluctuated during Quaternary, of fossils themselves as well, for these ten years. Major results are as follows: (1) Sedimentary facies and molluscan fossil contents of Quaternary sediments were originated from glacio-eustacy with the period of orbital precession and/or obliquity by the Milankovitch cycles. (2) Four stages in warm molluscan and diatom assemblages were recognized during the Holocene in Hokkaido. They can be correlated with the periods of strong northward inflow of the warm Tsushima were recognized at the Hyperthermal and Last Interglacial age. (4) Tsunami deposits, which consist of sand and sandy gravel with mixed environmental molluscan shells and wood fragments, generated by earthquakes were found along the Boso and Miura peninsulas. (5) A cold-seep chemosynthetic community, which is composed of the articulated bivalves Conchocela bisecta and Lucinoma spectabilis, were found in the lower Pleistocene Koshiba Formation, Yokohama City. (6) Living fossils were observed in seafloor caves, in deep water, or in singular area around spouting thermal spring on the ocean floor.