Three-Dimensional Delineation of the Pierre Shale Bedrock from Electrical Resistivity Surveys Conducted in Two Areas of Interest Within and Near Ellsworth Air Force Base, South Dakota, 2022

In 2022, the USGS, in cooperation with the U.S. Air Force Civil Engineer Center (USAF/CEC), performed geophysical surveys at two areas of interest within and near Ellsworth Air Force Base (EAFB) to delineate the Cretaceous Pierre Shale bedrock. Electrical resistivity tomography (ERT) data were collected in two grid patterns using the dipole-dipole array within and near EAFB and site information—including latitude, longitude, and elevation—were surveyed along geophysical transects comprising the grids using real-time kinematic (RTK) techniques. The purpose of collecting ERT data in grids rather than along individual transects was to create three-dimensional (3D) surfaces of the bedrock, which improve site characterization by providing [...]