The potentials and limitations of two taxa of terrestrial snails (polygyra spp. And euglandina rosea) as a source material for the radiocarbon dating of indigenous shell mounds and middens in florida, usa

Abstract

Preferred materials for radiocarbon dating are often rare on coastal archaeological sites, leading many archaeologists to date more common and abundant marine shells. But marine shell is often difficult to reliably radiocarbon date owing to the effects of the marine reservoir effect, especially where local environmental factors such as hardwater and limestone substrates complicate corrections. Terrestrial gastropods provide a potential alternative material for radiocarbon dating, although they are variably impacted by the same environmental factors and thus require testing to determine their reliability for dating archaeological deposits. We compare radiocarbon dating results from paired archaeological samples of wood charcoal and Odocoileus virginianus (white-tailed deer) bone with the shells of two terrestrial snail taxa—Polygyra spp. (flat coil snails) and Euglandina rosea (rosy wolf snails)—from the Cockroach Key archaeological site, in Tampa Bay, an open-water estuary on the western coast of the Florida Peninsula, USA. In one-third of the total 12 pairings, we found no statistically significant difference at the 95% probability level. For the other pairings, differences between snail shell dates and the reference dates ranged from decades to several centuries. Overall, our results suggest that both taxa have the potential to yield reliable radiocarbon dates, although not without complications.