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

Radiocarbon dates from known age, pre-bomb eastern oyster (Crassostrea virginica) shells provide local marine reservoir corrections (ΔR) for Chesapeake Bay and the Middle Atlantic coastal area of eastern North America. These data suggest subregional variability in ΔR, ranging from 148±46 14C yr on the Potomac River to −109±38 14C yr at Swan Point, Maryland. The ΔR weighted mean for the Chesapeake's Western Shore (129±22 14C yr) is substantially higher than the Eastern Shore (−88±23 14C yr), with outer Atlantic Coast samples falling between these values (106±46 and 2±46 14C yr). 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 ΔR corrections when calibrating 14C dates on aquatic specimens from the Chesapeake Bay and coastal Middle Atlantic region of North America.