Radiocarbon Marine Reservoir Ages in the Northwestern Pacific off Hokkaido Island, Japan, During the Last Deglacial Period

Abstract

We measured radiocarbon ages of planktic foraminifera in 4 sediment cores from the northwestern Pacific region off northern Japan in order to estimate marine reservoir ages during the Blling-Allerd period. The ages of deglacial tephra markers from 2 Japanese source volcanoes identified in these sediment cores had been previously estimated from 14C ages of terrestrial charcoal and buried forests. By comparing the foraminiferal and tephra ages, we estimated the surface water reservoir age during the Blling-Allerd period to be ~1000 yr or more in the region off northern Japan. The deglacial reservoir ages were more than 200 yr higher than the Holocene values of ~800 yr. The older deglacial ages may have been caused by active upwelling of deep water during the last deglaciation and the consequent mixing of older deep water with younger surface waters.