Geochronology of coastal prehistoric environments: a new closed system approach using amino acid racemisation

This study tested the feasibility of a closed system approach of amino acid racemisation (AAR) to provide reliable geochronological control for Quaternary coastal sites, crucial for the understanding of past climatic change and human evolution. An intracrystalline fraction of proteins was therefore isolated from several marine molluscan species and successfully tested for closed system behaviour with regard to protein diagenesis. The main focus was on the intracrystalline proteins within Patella: both modern shells, artificially degraded at high temperatures, and fossils. It was recognised that high temperature experiments are not necessarily able to mimic diagenesis at low temperatures, i.e. in fossils, and should be used with caution. Nonetheless, the extent of degradation of multiple amino acids within fossil Patella was successfully used for dating purposes. For the British record, a chronological framework was established from the historic period to the Middle Pleistocene. This was extended to the Late Pliocene/Early Pleistocene, using shells of Littorina, Nucella and Hiatella, although a “species effect“ was recognised which hampers the direct comparison of the kinetic patterns between species. The closed system approach using Patella was applied for the first time to areas characterised by warm climates: Northern Spain, Gibraltar and Morocco. Preliminary tests were also undertaken to aid future investigations of the chronology for the Red Sea (using Bursa and Strombus). The results from these studies have proved important for our understanding of human evolution, particularly with regard to exploitation of marine resources by Neanderthals and the origins of modern humans. Further studies should focus on better understanding the spatial localisation of the intracrystalline proteins, their composition and the kinetic pathways within the closed system. However, this approach successfully developed aminostratigraphic frameworks for Quaternary coastal sites in different areas of the world.