Measurements of the Marine Reservoir Effect on Radiocarbon Ages in the Eastern Bering Sea

Abstract

The marine reservoir effect is known to skew radiocarbon dating (marine samples appear "older" than terrestrial samples of equivalent age), but the magnitude of this effect is not the same in all locations. Carbon-14 age determinations from 23 paired samples of terrestrial and marine origin are presented for five areas around the northern and eastern Bering Sea. It appears statistically suitable to average the age differences for three pairs, weighted inversely by variance. Differences from within each of 14 pairs of wood charcoal vs. sea mammal residue (from St. Lawrence Island, Cape Prince of Wales, Nunivak Island, Alaska Peninsula, and Unalaska Island) yield a weighted mean of 737 ± 20 years. Somewhat more variant differences from within each of five additional pairs of wood charcoal vs. sea mammal residue (St. Lawrence Island, Unalaska Island) provide a lower weighted mean of 460 ± 41 years. Differences from within each of four pairs of wood charcoal vs. marine shell (Nunivak Island) produce a weighted mean of 459 ± 32 years. Variations in these apparent reservoir effects presumably result largely from the interplay of differential ocean water upwelling and customary faunal feeding areas, although possible effects of other species characteristics cannot be ruled out. Dating of marine samples from the Bering Sea should thus either proceed with the expectation that age determinations may not be accurate within several centuries, or be approached through experimental measurement of reservoir effect among restricted faunal species in limited areas. Overall, the effect throughout the eastern Bering Sea appears to range from about 450 to 750 years.