Influence of Mollusc Species on Marine Δr Determinations

C ages were measured on replicate samples of burnt grain and five mollusc species collected from a single, sealed layer at an archaeological site (Hornish Point) on the west coast of South Uist, Scotland. The aim was to examine the impact of using different mollusc species on ΔR determinations that are calculated using the paired terrestrial/marine sample approach. The mollusc species examined inhabit a range of environments and utilise a variety of food sources within the intertidal zone. Several authors have suggested that these factors may be responsible for observed variations in the C activity of mollusc shells that were contemporaneous in a single location. This study found no significant variation in the C ages of the mollusc species, and consequently, no significant variation in calculated values of ΔR. The implication is that in an area where there are no carboniferous rocks or significant local input of terrestrial-source carbonate to the surface ocean water, any of a range of marine mollusc species can be used in combination with short-lived terrestrial material from the same secure archaeological context to accurately determine a ΔR value for a particular geographic location and period in time.