Paleoceanography of the Oyashio Area during the Last 20, 000 Years Based on Benthic Foraminifera

Abstract

Benthic foraminifera in two cores, ST-5 and ST-21, collected from the Oyashio area show paleoenvironmental changes during the last 20, 000 years. Benthic foraminif eral fauna from both cores exhibit large changes during the last glacial-Holocene transition. Glacial fauna of core ST-5 closely resemble modern fauna living around a depth of 2, 000m under the confluence zone between the Kuroshio and Oyashio currents. This indicates that glacial paleoenvironments off Erimo Cape were similar to recent deep-water conditions under the confluence zone. However, Holocene fauna of core ST-5 show that carbonate dissolution has intensified in depths near 2, 000m. Glacial fauna of core ST-21 demonstrate that intermediate waters that originated from the northern North Pacific had intensified around a depth of 1, 000m. Middle and late Holocene fauna of core ST-21 reflect a low-oxygen condition similar to intermediate waters in the recent Oyashio area, although the area's oxygen level temporarily increased during the middle Holocene.