LOESSFEST'09 | Aug. 31st – Sept. 3rd, 2009 |Novi Sad-Serbia
Testing the Applicability of the Closed System Approach on Arianta Arbustorum for Further Use in Aar Dating
Pintér, A.G.1, Demarchi, B.2, Penkman, K.E.H.2, Kovács, J.1
1Department of Geology, University of Pécs, H-7624 Pécs, Hungary
2BioArCh, Departments of Biology, Archaeology and Chemistry, University of York, York, UK, YO10 5DD
Isolating a closed system in mollusc shells has proved vital for the reliability of amino acid racemization (AAR) dating in Quaternary geochronology. However, preliminary experiments for each species of shell are needed to determine whether a closed system can be isolated in the calcium carbonate matrix of the shells. Initially oxidation (bleaching) tests are undertaken on powdered samples, followed by further experiments on the kinetics of racemisation in the “intra-crystalline” amino acids.
These preliminary studies were carried out on Arianta arbustorum (LINNAEUS, 1758) a gastropod shell that is commonly found within loess deposits, and which therefore has potential utility for dating these sediments.
The bleaching results suggest that Arianta may not be suitable for geochronological applications, due to the lack of a completely isolated “intra-crystalline” protein fraction. Although an abrupt decrease in concentrations upon bleaching is seen showing a similar pattern to that found in other species, changes in D/L values do not seem to follow such patterns. The kinetic experiments begin to provide a better understanding of this phenomenon, and may enable us to predict which shells are suitable for AAR. The study confirms that these preliminary experiments need to be carried out before application of the new technique for dating purposes.