The LSU Campus Mounds: New Investigations Using Synchrotron Radiation–Based Techniques

Abstract In a recent publication, Ellwood et alia (2022) presented results indicating that the LSU Campus Mounds (16EBR6) could be the oldest man-made extant structures in the Americas, that they were built in phases with a hiatus of approximately 2,000 years, and that they were used for ceremonial fires or cremations. In a subsequent publication, McGimsey et alia (2022) expressed their concerns regarding the conclusions presented in the Ellwood et alia publication. To resolve some of the controversial issues, McGimsey et alia identify six avenues for further research. In this article, we address selected aspects of four of these recommendations using synchrotron radiation (SR)–based techniques. SR-X-ray fluorescence spectra show no significant differences in the elemental concentrations of samples from various possible construction phases and in the concentration of samples from lighter-colored (ash?) and darker areas. For iron (Fe; a temperature-sensitive element) and for silicon (Si; the characteristic element for phytoliths), the corresponding X-ray absorption spectra show no significant differences in the chemical state between light- and dark-area samples. These results support neither the assumption that Mound B was built in two phases with a long hiatus nor the assumption that light-colored lenses consist of ash from hot fires.