Thermal Influences on Shells: an Archaeological Experiment from the Tropical Indo-pacific

Thermal influences on marine molluscs are poorly understood across all disciplines, including archaeology. This presents potential issues for further analysis including radiocarbon dating and stable isotope analysis, as well as hindering our understandings of processing and preparation methods for shell in the past. Different methods of burning or heating may not always leave visual signs on a shell; however, a variety of structural and chemical changes may take place. Here, we present an experimental study using modern-day shells of five tropical marine species designed to explore how various thermal interventions modified shells in terms of microstructure (scanning electron microscope) and mineralogy (X-ray diffraction). We found distinct differences between the taxa using varied temperatures and durations, with shell microstructure playing a key role in responses to thermal stresses. This study highlights the importance of acknowledging this variation, both when structuring research as well as seeking to interpret archaeological shell remains.