Sub-centennial resolution amino acid geochronology for the freshwater mussel Lampsilis for the last 2000 years

摘要

We present an amino acid racemization-based age calibration with sub-centennial resolution from historical specimens of several species of the freshwater mussel genus,. Lampsilis, from multiple river basins in the eastern United States. Valve samples that were bleached to isolate the intra-crystalline fraction of amino acids resulted in more consistent amino acid concentration and D/L values amongst duplicate sub-samples than those subjected to standard sample preparation techniques; therefore bleached samples are preferable for this geochronological application. The relation between D/L and age was determined for historical specimens housed in museums, allowing for the age determination of valves stored at room temperature for up to 150 years. We derived the Arrhenius parameters for the racemization of aspartic acid and glutamic acid by combining the results of heating experiments using live-collected specimens with data from museum specimens. This allows the determination of age for undated samples that lived during the last 2000 years and that experienced a range of post-depositional thermal histories. The procedure provides an accurate and low-cost geochronological tool for studies in biology, geology, environmental science, and conservation biology and paleobiology.