QUANTIFYING THE MARINE RESERVOIR EFFECT FOR EARLY HOLOCENE SOUTHEAST ALASKA

This project contributes new data for the approximation of the early Holocene marine reservoir effect in southeast Alaska. Variability in ocean water composition across both time and space influence the apparent radiocarbon age of marine shell, requiring local calibrations to account for the marine reservoir effect. Previously available data for the region were limited to eight data points from the northern half of southeast Alaska (weighted mean delta R of 520 +- 80, McNeely et al., 2006, accessed on the 14Chrono Marine Reservoir database at calib.org) and five points from Haida Gwaii in British Columbia (weighted mean delta R of 265 +-80, same source). We present 34 shell-wood pairs from secure contexts in early Holocene raised marine terraces from Baranof, Kupreanof, Kuiu, Heceta, Kosciusko and Prince of Wales Islands. For southern southeast Alaska in the early Holocene the average reservoir age is 710 +- 70, with a range of 240 to 1000 years (comparable to reservoir ages for coastal British Columbia in Southon and Fedje 2003 and Hutchinson et al. 2004); the resulting weighted average of delta R values is 365 +-80, ranging from -90 to 625. These data reflect relationships with McNeeley et al.’s samples both to the north and south of our sampling region, and provide confidence for future radiocarbon dating of marine shell for use in paleoshoreline modelling and dating archaeological contexts.

Delta R values calculated using online deltar software (Reimer and Reimer 2016) with IntCal13 and Marine13 calibrations (Reimer et al. 2013).