Phytolith radiocarbon dating in archaeological and paleoecological research: a case study of phytoliths from modern Neotropical plants and a review of the previous dating evidence.

Recent carbon-14 studies of phytoliths from modern plants collected from extra-tropical regions of the world have yielded dates that are too old by several hundred to thousands of years. These findings have prompted questions about the suitability of phytolith-derived carbon for dating in archaeological and paleo-environmental research. In this paper, phytolith 14 C ages are determined from a number of modern Neotropical plant taxa collected between 1964 and 2013. The specimens studied are maize ( Zea mays L.), two squash species ( Cucurbita ecuadorensis H.C.Cutler & Whitaker and C. ficifolia Bouche), and two trees common in Neotropical forest, Hirtella americana L. and Socratea durissima (Oersted) H. Uendl. They represent families, genera, and species that are well-represented in Neotropical archaeological and paleoecological sediments. Every phytolith sample returned a post-bomb 14 C phytolith age reflecting collection after 1955, with the exception of a herbarium specimen that was treated with chemicals containing radiocarbon-dead carbon. The phytolith dates do not indicate a source of extraneous old or young carbon occurring on the surfaces or inside of phytoliths that bias their ages. Such findings are also reflected by previous phytolith 14 C studies of ancient Neotropical sites. Possible reasons for the differences in results between these and other studies and varying interpretations of soil and sediment phytolith 14 C analyses by different investigators are discussed. [ABSTRACT FROM AUTHOR]