This presentation is part of the International Cemetery Preservation Summit, October 8-10, 2014 Niagara Falls, NY.
Finding Avondale: Remote Sensing for an Unmarked Cemetery in Difficult Subsurface Conditions by Hugh B. Matternes and Valerie Davis
One of the most challenging tasks for cemetery researchers is to positively identify the location of unmarked cemeteries. In central Georgia the problem is compounded by the presence of undisturbed beds of Saprolite, the deeply weathered remains of metamorphic rock, more affectionately known as Georgia red clay. These clays are extremely dense, are prone to re-compact relatively soon after disturbance, and they contain significant amounts of iron, making the application of non- and minimally-invasive remote sensing techniques a challenge. When left undisturbed for many decades, bioturbation will erase surface characteristics that can normally be used to help identify unmarked grave details. Our need to identify the location of the Avondale Burial Place (9BI164), an unmarked cemetery in southern Bibb County, Georgia, provided an opportunity to compare how different techniques fared in a worst-case scenario.
The Avondale Burial Place was a nineteenth- through early twentieth-century rural folk cemetery used by a dispersed community of African-American sharecroppers and farm laborers. The cemetery occupied the corner of a land lot on a slight rise of red clay that in all likelihood was never plowed. We ultimately determined that the grounds held the remains of 101 individuals, placed in an east-west orientation, and arranged in what appeared to be loosely organized family clusters. There were no grave markers present, but the ephemeral scatter of glass, potsherds, toys, and tile fragments emphasized that the community probably decorated grave surfaces following African-American folk cemetery traditions. These materials only approximated the general area of the cemetery and provided no information on individual grave locations.
While limited testing confirmed the presence of the cemetery, its exact size and distribution was unknown. Three methods of remote sensing, including soil compaction (or probing), ground-penetrating radar, and canine detection (cadaver dogs) were employed to help define the cemetery’s boundaries. The location of each potential grave was mapped during each survey. Based on the distribution suggested by these methods, we used heavy equipment to remove all surface deposits to expose the underlying grave shafts. While this provided us with the true location of each interment, it also generated a means of examining the effectiveness of each remote sensing method.
The results of the soil compaction survey revealed a highly irregular pattern of soil compaction immediately beneath the surface that likely reflected more recent natural intrusions (burrows and roots). Potential grave shafts were not detected and the method was determined to be ineffective for the given environment. Using ground-penetrating radar, a total of 71 anomalies were interpreted as potential graves. Only 32 (45%) of these ultimately corresponded with true graves. Many of the false positives were in areas that were determined to be outside the cemetery. Scent-detection dogs specially trained in grave identification by the Alpha Team Search and Rescue group, were employed to define the cemetery. Of the 60 positive alerts generated by these animals, 16 (26%) positively corresponded with true graves. While canine success rates for identifying individual graves were lower than GPR rates, canine alerts were more concentrated to within the burial ground. Most of the false positives outside the cemetery were associated with areas where equipment used in previous burial recoveries by New South had been stored.
While ground-penetrating radar was able to more accurately define the location of individual graves, its results included extra-cemetery anomalies that inflated the size of the burial ground. In contrast, canines were less able to define exact locations for individual graves; however, their alerts more accurately pinpointed the cemetery’s true location. The results from our triad of remote sensing techniques emphasized that the application of multiple methods can result in different, yet complimentary information. Given that some methods may be ineffective, particularly when faced with adverse subsurface environments, the use of multiple remote sensing methods is advocated to provide more accurate estimates of the location and size of unmarked graves and cemeteries.
Dr. Hugh B. (Matt) Matternes of New South Associates is the Director of the Cemetery Studies Program, where he is responsible for the identification, preservation, and recovery of cemetery sites, and the professional and ethical treatment of human remains. He received his B.A. in Anthropology from the University of North Carolina, Greensboro, his M.A. and Ph.D. in Anthropology with a focus in physical anthropology and mortuary archaeology from the University of Tennessee, Knoxville. He is a Registered Professional Archaeologist (RPA) with over 28 years devoted to studying cemeteries. He is the author or co-author of over 80 technical reports and professional publications. His research interests currently focus on community dynamics as reflected in post-Reconstruction era African American cemeteries.
Valerie S. Davis
Valerie Davis is a professional Mortuary Archaeologist and Physical Anthropologist at New South Associates, Inc. where she supervises field and laboratory cemetery investigations. She is a Registered Professional Archaeologist (RPA) with over 13 years of experience, and is proficient in identifying folk and ephemerally marked cemeteries, documenting surface and subsurface mortuary data, as well as conducting in-field and laboratory analysis of human remains. She received her BA in Anthropology and her MA in Anthropology with a focus on Bioarchaeology from Mississippi State University.