Dating marine shell in Oceania: Issues and prospects

Abstract

Marine shell has several advantages for radiocarbon (¹⁴C) dating in the Pacific — it is ubiquitous in archaeological sites, is easy to identify to the species level, and can often be related directly to human activity. Consequently, shells are one of the most commonly dated ¹⁴C sample types within this region. The modelled marine calibration curve and associated regional offsets (known as ΔR) originally constructed by Stuiver et al. (1986), have been widely accepted as the most accurate method for calibrating surface marine ¹⁴C dates. The use of published values, however, is not straightforward because the surface ocean ¹⁴C reservoir is variable both regionally and over time, and because of additional uncertainties with the reliability of some shell species due to habitat and dietary preferences. This paper presents an overview of ΔR variability in Oceania and highlights areas of caution when using extant ΔR values, and when selecting marine shell for ¹⁴C dating. Particular attention is given to the Hawaiian archipelago where numerous ΔR values are available for evaluation and the influence of ocean currents, estuarine environments and geology is apparent.