Combining ER and GPR surveys for evidence of prehistoric landscape construction: case study at Mound City, Ohio, USA

• GPR and Electrical Resistivity defined the remnants of a clay loam liner that appears to have been emplaced by the Hopewell.
• A strong relationship was observed between the GPR and ER data for distinguishing ultra-shallow soil textural changes.
• GPR and ER results support a new interpretation that the pits at the Mound City site served as cultural landscape features.

Mound City, located at the Hopewell Culture National Historical Park in south-central Ohio, USA, is a prehistoric earthwork (200 BC–500 AD) that consists of 24 mounds enclosed in a square embankment wall and is surrounded by eight pits. Recent excavation of two of these pits resulted in the discovery of a clay loam liner that appears to have been placed on the floor of the pits by a prehistoric society known as the Hopewell. The aim of this study was to determine the spatial pattern of this liner in one of the pits using non-invasive geophysical techniques, specifically electrical resistivity and ground-penetrating radar. Minimally invasive soil augers and a test trench yielded information that was used to corroborate interpretations of the geophysical data. The geophysical methods proved to be useful in locating and defining the remnants of the prehistoric clay loam liner, and the results of our investigation indicate that almost 50% of the liner still remains in the pit today. This discovery supports a new interpretation that the Hopewell excavated and preserved the pits at the Mound City site because they served as cultural landscape features.