The Effect of Settlement Reoccupation on Electromagnetic Induction Data Sets in Archaeology (pp. 349-362)
Authors: (Daniel P. Bigman, University of Georgia, Athens, Georgia, USA)
Abstract: This chapter compares results of electromagnetic induction surveys from two archaeological contexts, Drake’s Field and Southeast Plateau, located at Ocmulgee National Monument in Macon, GA. One is a single component area and the other a multi-component area. This survey was conducted to understand large, landscape scale, human settlement patterns in an efficient, cost effective manner without disturbing the archaeological record. I carried out field tests using a soil conductivity meter in continuous data collection mode at a frequency of 12150 Hz. I collected 6 to 9 measurements per meter and spaced transects 1 m apart. The conductivity meter recorded more variation in apparent conductivity values (mS/m) for the reoccupied site (Southeast Plateau). The two data sets differed in interpretability of horizontal grey scale plots and single traces of apparent conductivity values. Drake’s Field resembled similar surveys of single occupation sites. I could interpret anomalies as specific features and patterned clusters of anomalies as buildings. However, 4,000 years of human reoccupation on the Southeast Plateau left a high density of archaeological remains including postholes, hearths, burials, storage pits, and garbage pits.
The density of features results in overlapping electromagnetic signatures and anomalies cannot be attributed to specific feature types nor can the location of a specific anomaly be accurately determined. Despite the difficulty in interpreting electromagnetic data sets from reoccupied sites, an important recognition came from this comparison: archaeological sites containing multiple reoccupations yield a specific and recognizable electromagnetic signature. This signature reflects the complicated subsurface modifications made by humans throughout history and can be distinguished from contexts of single occupancy and presumably from unoccupied zones. Archaeologists could potentially use this method for rapid assessment of occupational intensity or length.