Through the Looking-Glass, and What Amino Acids Found There

Abstract:

Timing is everything: accurate dating of the geological record is essential to an understanding of our Earth's history. Chronology underpins our understanding of the past, but beyond the limit of radiocarbon dating (~60 ka), sites become more difficult to date. Amino acid geochronology uses the time-dependent breakdown of proteins in biominerals, with the racemisation reactions (conversion between mirror-images) of amino acids having the potential to date the whole of the Quaternary. Recent studies have shown that a very small fraction of ‘intra-crystalline’ protein within mollusc shells, opercula and eggshell forms a closed system, and if this is targeted, the difficulties due to leaching, contamination and environmental factors are removed. The analysis of a coherent calcite intra-crystalline system has enabled the development of a robust chronology for Britain back to at least 2.8 Ma.

Correlation of Quaternary sequences, even in adjacent regions, is often problematic, but the development of regional aminostratigraphies promises to provide robust chronologies, enabling more confident correlation. The calcitic opercula of bithyniid (or similar) gastropods occur commonly in many Quaternary sequences, offering potential for development and correlation of regional aminostratigraphies around the world. Extending the British framework to continental Europe (and beyond) is one of the first steps, and we present preliminary results from analyses of a series of key archaeological and palaeontological sites from across northern Europe from France to Russia. In order to build the most comprehensive framework possible, we are targeting type localities for various interglacial stages, as well as horizons that can be related to glacial sediments, river terrace sequences, biostratigraphy and archaeology. We have tested the technique against other geochronological techniques, and a detailed understanding of the temperature effects on the extent of protein breakdown allows us to make comparisons between regions, and correlations to the marine oxygen isotope record. Our research focuses on building chronological frameworks on a wide spatial and temporal scale, and ever expanding the range of materials we are testing.