CHARACTERIZATION OF SUBSURFACE GLACIAL SEDIMENTS IN NORTHWEST PENNSYLVANIA USING NON-INTRUSIVE GEOPHYSICAL METHODS

Glacial sediments in the shallow subsurface in the vicinity of Corry, Pennsylvania were evaluated using multichannel analysis of surface waves (MASW), electrical resistivity (ER) and induced polarization (IP) geophysical methods. The project area encompassed approximately 11 square miles and the maximum depth of investigation was up to 300 feet below ground surface.

ER and MASW data indicated localized patterns of resistivity and shear wave velocity measurements that correlate with coarse grained gravels to fine grained silts in drilling logs from nearby water wells. In addition, the entire sequence of glacial overburden is distinguished from the underlying Paleozoic bedrock via resistivity and shear wave velocity contrasts in the geophysical data. Measured IP responses were minimal throughout the survey.

Seven distinct geophysical signatures were developed from correlations with numerous well logs in the study area including fine-grained deposits, poorly consolidated sand and silt, water-bearing sand and gravel, variably saturated sand and gravel, well-consolidated lodgement till, layered till with variable grain size, and shaley siltstone bedrock. Recommended future studies include conducting high resolution geophysical surveys for water supply investigations or other types of natural resources and using ER and MASW data to establish aquifer parameters for numerical groundwater models in these types of terranes.