Calcitic dung spherulites and the potential for rapid identification of degraded animal dung at archaeological sites using FTIR spectroscopy

Animal dung is increasingly a valuable resource for reconstructing ancient activity in archaeology. One of the most common archaeological indicators of dung in caves and arid environments are calcitic dung spherulites that form in the digestive system of a variety of animals. Although many aspects of their formation and taphonomy are understood, details of their mineralogy remain poorly-defined. Using the Fourier transform infrared (FTIR) grinding curve method, we report here that archaeological sediments containing large amounts of dung spherulites can be differentiated from sediments composed of other forms of geogenic and pyrogenic calcites. We propose that this attribute can be used to rapidly identify well-preserved degraded dung deposits at archaeological sites with routine laboratory or on-site field FTIR analysis. This observation at a 5000-year-old open air site suggests that the grinding curve method also has potential to be used for assessing preservation of dung spherulites for future radiocarbon or stable isotope investigations.