We tend to think of cemeteries as places where time has stopped, yet cemeteries are cultural products with a history. A number of natural and cultural processes act to transform these places over time, often obscuring those features that allow us to recognize individual graves or even entire cemeteries. A critical and long-standing challenge in the preservation field has been finding unmarked graves.
Near-surface geophysical techniques would appear ideally suited to solve this problem. Not only are they efficient, but in contrast to excavation techniques, they allow one to "look" into the ground without disturbing the graves they are attempting to find. Yet countless projects involving a battery of methods have left researchers less than satisfied. These surveys do not guarantee that all or even most graves are found and they often confuse graves with other sources of disturbance.
Using a PTT grant, researchers Rinita Dalan (Minnesota State University Moorhead), Steven De Vore (National Park Service, Midwest Archeological Center), and Berle Clay (Cultural Resource Analysts, Inc.) tested a new approach using minimally-invasive down-hole geophysical measurements aimed at improving near-surface geophysical results. Their research involved the use of a magnetic susceptibility sensor introduced down a small diameter (approximately 1 inch) hole made with a hand-held corer together with magnetic analyses of soil samples to recognize soil disturbance associated with the excavation and refilling of grave shafts.
Partnering with the Sac and Fox of Missouri and the Iowa Tribe of Kansas and Nebraska allowed them to test this approach at two Native American family cemeteries in Nebraska and Kansas. In conjunction with an excavation project conducted by the Kentucky Archaeological Survey, they were able to test down-hole techniques for grave shaft recognition and to also investigate magnetic properties of burials.
Their investigations revealed a distinctive magnetic signature for grave shafts related to differential soil compaction, often most apparent at depths not tested by soil compaction instruments. Thus, down-hole measurements could be employed to evaluate whether near-surface geophysical targets actually corresponded to grave shafts or even to explore targeted areas where graves were suspected. Their limited studies of burials indicated magnetic characteristics associated with interments that might be used, in excavation contexts, as a means of burial identification where grave goods and skeletal remains are lacking. Although not a replacement for near-surface surveys, these techniques show promise for improving capabilities in the identification, evaluation, and thus the preservation of graves.