Marine radiocarbon reservoir corrections (∆R) for Chesapeake Bay and the Middle Atlantic Coast of North America

Abstract

Radiocarbon dates from known age, pre-bomb eastern oyster (Crassostrea virginica) shells provide local marine reservoir corrections (∆R) for Chesapeake Bay and the Middle Atlantic coastal area of eastern North America. These data suggest subregional variability in ∆R, ranging from 148±46 14Cyr on the Potomac River to −109±38 14Cyr at Swan Point, Maryland. The ∆R weighted mean for the Chesapeake's Western Shore (129±22 14Cyr) is substantially higher than the Eastern Shore (−88±23 14Cyr), with outer Atlantic Coast samples falling between these values (106±46 and 2±46 14Cyr). These differences may result from a combination of factors, including 14C-depleted freshwater that enters the bay from some if its drainages, 14C-depleted seawater that enters the bay at its mouth, and/or biological carbon recycling. We advocate using different subregional ∆R corrections when calibrating 14C dates on aquatic specimens from the Chesapeake Bay and coastal Middle Atlantic region of North America.