Amino acid ratios and the correlation of raised beach deposits in south-west England and Wales

Abstract

Interest in studies of amino acid racemisation as a framework for Quaternary chronostratigraphy has increased recently^1–4. These studies have used different materials, but the main two substances have been bone and shell. Different shell genera can have different rates of racemisation⁵, so the use of new genera requires some study of the kinetics of the reactions before the results from one taxa can be compared to another. We report here the successful application of amino acid racemisation studies on the limpet Patella vulgata as a basis for correlating the scattered raised marine beaches of interglacial age(s) from south-west England and Wales. We show that the epimerisation of D alloleucene: L isoleucene (D allo: L iso) in P. vulgata, provides a useful basis for regional correlation. This mollusc lives attached to rocks above the mean tide level and, hence, spends a good portion of its life living at the ambient air temperature. We suggest that the fossil material may have been primarily exposed to regional atmospheric climate since death, because all available evidence points to sea level being lower than present during much of the past 120,000 yr (ref. 6).