Radiocarbon ages of raised‐beach shells from Oronsay, Inner Hebrides, Scotland: a lesson in interpretation and deduction

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Abstract
Comparison of radiocarbon ages of raised‐beach shells from sites in the proximity of Mesolithic shell middens on Oronsay illustrates the importance of correct interpretation of the significance of the stratigraphical, ecological and archaeological contexts of dated shells. A difference of c. 3000 years between the determined ages of shell samples of Patella and Arctica from the same horizon in a raised beach and smaller but significant differences in the ages of shell samples of the same genera and other genera from four horizons within a raised storm beach may have been caused by combinations, in varying degree. of isotopic fractionation, isotopic replacement, depleted initial 14C activity and the hard‐water effect. Comparisons are made with published accounts of similar problems encountered in dated raised‐beach shells from west Greenland, Finnmark (north Norway) and south Wales.