Paleoceanographic control on a large marine reservoir effect offshore of Tokai, south of Japan, NW Pacific, during the last glacial maximum-deglaciation

Abstract

Knowledge of the marine reservoir effect is important in calibrating radiocarbon ages to calendar ages, and in correlating geologic and paleoceanographic events among different sites, including global events. Large, explosive volcanic eruptions have yielded numerous volcanic ash layers (tephras) over geological time. Because tephra layers are deposited both on land and upon the seafloor, they represent a unique and important link between the geological records of terrestrial and marine areas. Comparison of the radiocarbon ages of a tephra layer deposited in marine (planktonic foraminifera) and terrestrial (peat) materials reveals a local marine reservoir age (600–700 years or more) during the early part of the last deglaciation off Tokai, south of Japan. This age is larger than that determined for the present-day Pacific coast of Japan (82 years) and similar to that of the present-day subarctic NW Pacific (350–580 years). This difference between modern-day and deglaciation marine reservoir values is thought to reflect the contrasting properties of surface water masses between the two periods.