Reservoir Effect of Coastal Waters off Western and Northwestern Galicia

Abstract

Differences in the radiocarbon ages of closely associated marine mollusk shells and terrestrial material (charred wood or bones) from several Galician archaeological contexts are significant from the Iron Age to Medieval times. Delta-R values show high variability, ranging from 280 +/- 70 to 270 +/- 40 14C yr. The set of Delta-R values also presents a strong positive peak (Delta-R = 270 +/- 40 14C yr) at 860 +/- 90 BP, which matches another peak found for western Portuguese coastal waters. The data obtained, namely the negative or close to zero R values, suggest that the reduced offset between atmospheric and surface water 14C content is due to the existence of a strong stratification of the water column and environmental factors in the Galician rías during the Iron Age and the Medieval period.