Radiocarbon ages were measured on replicate samples of burnt grain and 5 mollusk 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 mollusk species on ΔR determinations that are calculated using the paired terrestrial/marine sample
approach. The mollusk species examined inhabit a range of environments and utilize a variety of food sources within the
intertidal zone. Several authors have suggested that these factors may be responsible for observed variations in the 14C activity
of mollusk shells that were contemporaneous in a single location. This study found no significant variation in the <sup>14</sup>C ages of
the mollusk 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 inputs of freshwater to the surface ocean, any of a range of marine
mollusk 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
