A Multistage Geophysical Approach to Detecting and Interpreting Archaeological Features at the LeBus Circle, Bourbon County, Kentucky

Abstract

ABSTRACTMagnetic gradiometry and in‐phase electromagnetic induction (EM) instruments were employed during a geophysical survey to identify archaeological features at an Adena circular ditch and embankment earthwork site. Three features identified in the geophysical survey were selected for further geophysical examination because of their shape, spatial arrangement, and differences in the gradiometer and EM data. Downhole magnetic susceptibility was used to explore the subsurface shape of these features and to identify the presence of magnetic variations within them. Excavation of these features exposed a buried ground surface below the earthwork's embankment, a midden‐like soil in the ditch, and a large pit situated over a spring/seep inside the earthwork. Magnetic susceptibility data were collected on open wall profiles of excavation units with a KT9 kappameter. Pairing the geophysical results and excavation profiles helped separate a lightly burned ground surface from a buried A horizon below the embankment, map the buried A horizon beneath areas where the embankment is now destroyed, and separate natural from cultural fill episodes inside the pit feature. Correlations between the magnetic susceptibility data and drawn profiles identified specific cultural contexts for radiocarbon dating. The radiocarbon chronology of the site indicates the earthwork was constructed during Middle Adena ritual development (150 bc to ad 1), a time marked by increasing ritual diversity and the appearance of circular structures used in mortuary ritual. This research also demonstrated that the Woodland earthwork was reused by Late Fort Ancient peoples after approximately ad 1450. Copyright © 2011 John Wiley & Sons, Ltd.