T03_12

The comparison of four ¹⁴C pretreatment methods applied to archaeological shells from Vale Boi (Portugal).

Paleček D¹, Falini G¹, Wacker L², Bicho N³, Talamo S¹

¹Department of Chemistry G. Ciamician, Alma Mater Studiorum University of Bologna, Bologna, Italy, ²Laboratory of Ion Beam Physics, ETH, Zürich, Switzerland, ³Interdisciplinary Centre for Archaeology and the Evolution of Human Behavior, University of Algarve, Faro, Portugal

Mollusc shells are often found in archaeological sites, given their great preservation potential and high value as a multipurpose resource. Vale Boi (Algarve, Portugal) is a well-known Upper Paleolithic archaeological site representing the earliest recorded modern human occupation in southwestern Iberia, as attested by the Early Gravettian remains dated to c. 32 ka Cal BP. The continued use and importance of mollusc shells at this site is attested by their presence throughout the long stratigraphic sequence. Thus, it is especially important to determine their age and purpose at the site.

Radiocarbon (¹⁴C) dating is a field in constant improvement; sample pretreatment chemistry is addressed by laboratories across the world, with the continuous development of new and improved protocols. Nevertheless, the pretreatment method for mollusc shells has not changed since the first application and is still used in many laboratories, although a new protocol was introduced in 2010. In our new ¹⁴C lab (BRAVHO) at Bologna University, we tested and applied these two methods in order to compare them. Furthermore, we introduced two alternative methods to extract the organic matrix from the shell, as it is protected from the environment and should reveal the true age of the shell. Here, we compare the ¹⁴C dates obtained to determine the most reliable pretreatment method for mollusc shells. The results of this study will give us the possibility to construct precise chronologies for sites such as Vale Boi, where shells are abundant throughout the stratigraphic sequence.