Late Pliocene-early Pleistocene paleoceanographic evolution of the Sea of Japan

The stratigraphic distribution and abundance of molluscs and planktonic for aminifera within a sixth-order (41 kyr) depositional sequence of the early Pleistocene Omma Formation in central Japan provide several important infor mation on the Sea of Japan since 2.5 Ma. The sea possibly experienced three substages in the paleoceanographic history since then. During substage 1 ( 2.5-1.71 Ma, oxygen isotope stage 60/59), cold northern surface water preva iled due to the closure of the sea's southern entrance. During substage H ( 1.71-1.52 Ma, stage 51), the warm Tsushima Current flowed into the sea from the south during interglacial highstands. During substage III (1.52-0 Ma), isolation of the Sea of Japan was reinforced by narrowing and/or shallowin g of the northern entrance. These changes were caused by some local tectoni c movements that affected topography of the southern and northern straits. Inflow of the Tsushima Current resulted in mi.-ration of warm-water organis ms into the Sea of Japan during interglacial stages, and acted as a barrier to the migration of terrestrial organisms between East Asia and Japanese I slands. (C) 2001 Elsevier Science B.V. All rights reserved.