Modern radiocarbon offsets within the land snails Cyclophorus: a tropical karst case study from Northern Vietnam
This thesis forms part of the SUNDASIA project on the archaeology of the UNESCO World Heritage Site Tràng An (Ninh Bình, Northern Vietnam), a tower karst area of high endemism and habitat insularity. Archaeological sites in the region contain abundant shell middens, composed mainly of terrestrial Cyclophorus molluscs. The reliable interpretation of radiocarbon (14C) dates of terrestrial mollusc shells depends on an understanding of their ecology and behaviour as well as the geology of the area. Since gastropods feed by substrate scraping, they are prone to biased radiocarbon dates as they can incorporate 14C-deficient or dead carbon in their shells. Even though shells are commonly found in archaeological midden deposits, they are avoided for radiocarbon dating, especially those from karstic regions. Live terrestrial Cyclophorus species and associated vegetation were collected on limestone outcrops from the Tràng An area. The results indicate that the shells uptake a considerable amount of dead carbon. A localised reservoir offset for Cyclophorus 14C ages is estimated. Being able to reliably correct radiocarbon dates for this offset will set the basis for a better understanding of the role played by prehistoric middens in the Tràng An region.
Networked Digital Library of Theses and Dissertations