GPR for detecting buried animal bones in controlled sandbox experiments

Bone-beds can provide a wealth of information at archeological sites, including age of the site, site formation processes, seasonality of the kill, size and gender of the herd, and paleoenvironmental conditions at the time of the kill. Ground-penetrating radar (GPR) is a non-invasive, cost-effective technique that has the potential to delineate the horizontal and vertical limits of bone-beds in different geomorphological settings. Furthermore, the identification of a bone signature from geophysical methods can have modern day applications, particularly in forensic research investigations. There have been previous attempts, mostly in forensic studies and studies that involve mapping graveyards, to locate buried bone using geophysics. Although geophysical tools have successfully identified buried remains of homicide victims and the location of graves, these finds resulted from the identification of anomalies related to the disturbed soil in graves and not to an anomalous signal from the bone itself. It is necessary to detect the signal from the bone at these archaeological sites, because prehistoric animal remains typically were not buried immediately upon death, but instead became covered over time by sediment. Initial lab experiments determined the electrical properties (i.e. the relative permittivity, loss factor, and loss tangent values) of modern animal bone and indicate that bone is a desirable low-loss target for GPR detection. In order to test these results, we have built a 1x2x1 meter sandbox and placed modern bison bone inside of it to simulate natural burial conditions. This research presents successful GPR detection of the vertical and horizontal extents of the buried bison bone. In addition, changes in variables such as depth of burial, size and shape of target, and antenna orientation are presented to assess the overall detection capability of GPR for this unique archaeological feature.