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Two reflection seismic transects, one across the central Appalachians in Virginia and the other across the southern Appalachians in Georgia, reveal a significant contrast in mid- and lower crustal reflectivity from east to west. Data from east of the Blue Ridge geologic province in Virginia and to the east of the Inner Piedmont in Georgia show a highly reflective crust extending from the near-surface to the Moho, including zones of east-dipping reflections, a sub-horizontal reflection signature at ∼7 seconds, and a west-dipping Moho. Reflection seismic data from west of the Blue Ridge in Virginia and Inner Piedmont farther south are characterized by reflector geometries related to deformation above a master decollement, leading to classic ‘thin-skinned’ tectonic structures in the overlying allochthon, and few if any apparent structures in the underlying basement. The location of the Iapetan rifted margin, the preexistence of favorably oriented structures to the east of this point, and sub-horizontal weak zones within the lower Paleozoic shelf strata have played critical roles in the distribution of seismic reflector geometry. Seismic reflection signatures seen in the southeastern United States are a result of multiple episodes of deformation from the early Paleozoic through the middle Mesozoic. Oblique stresses during late Paleozoic time produced transpression that manifested itself as predominantly strike-slip faulting to the east of the Blue Ridge/Inner Piedmont. Onlapping lower Paleozoic shelf strata responded to tectonic stresses through thin-skinned deformation above a master decollement during the late Paleozoic Alleghanian orogeny, aided in part by sub-horizontal zones of weakness in the strata. This partitioning of strain was supported via tectonic buttressing provided by Precambrian continental crust that was little deformed in the Taconic orogeny. During the Alleghanian orogeny, the variations in Valley and Ridge deformational style between the central and southern Appalachians were controlled by the original shape of the continental edge. Further deformation during Mesozoic extension occurred to the east of the Precambrian rift margin in the region where favorably oriented faults were reactivated, leading to the rotation of the fault zones from more steeply dipping initial orientations, the merging of the mid-crustal reflection zone with the Moho, and the formation of Mesozoic basins and antiformal reflections in the seismic sections.

Electrical resistivity and induced polarization (IP) measurements were made to explore the variability of electrical parameters within tar-contaminated soils at the site of a former shingle manufacturing facility on the floodplain of the Oswego River in Fulton, NY. Degradation of the buried shingles generated diapirs of tar, which extrude onto the surface, creating self-replenishing “tar boils” at the site. Data from offset Wenner electrical resistivity surveys conducted in December of 1997 and 1998 were used to delineate highly resistive areas believed to be associated with the tar. Trenching and drilling after the 1997 effort revealed tar in some of the resistive zones; other resistive zones contained large sandstone boulders believed to be associated with the building of the Oswego River Barge Canal. Known and potential tar-contaminated zones were the focus of IP surveys conducted in May through July of 1999. The field experiments conducted at this site were designed to test the ability of IP parameters to distinguish between types of resistive zones in the subsurface. Both dipole-dipole and gradient data were collected, targeting zones with the highest resistivity and surface tar boils. Results indicate that maps of chargeability at early times on the decay curve indicate the presence of tar. In addition, Cole-Cole parameters calculated from the decay curve for exponent c = 0.25 were used to generate amplitude, phase and critical frequency values. Maps of these values also separate zones of tar contamination from sandstone boulders and other resistive zones.

Electrical resistivity measurements were made to determine the variability of surficial deposits, the depth to bedrock and to characterize the distribution of groundwater at the Rice Creek Field Station near Oswego, New York. The field station is underlain by drumlin deposits and ablation till associated with Pleistocene glaciation. These deposits reside on Ordovician quartz sandstone of the Oswego Formation that outcrops within 1500 m of the study site. Locally the Oswego Formation contains subvertical fractures with an average spacing of less than 0.5 m. Twenty offset Wenner electrical resistivity surveys were conducted in June and August of 1998 along trails and across an open field within the field station grounds. Analysis of pseudosections and simple 1-D modeling and 2-D least squares inversion indicate the following: 1) low resistivity zones associated with perched water tables within the chaotic drumlin deposits; 2) highly variable and resistive near-surface measurements along Rice Creek indicative of large (>l m diameter) glacial erratics as observed in the creek bed; 3) a transitional zone below -250 ft elevation of subcircular highs separated by relatively low resistivities that continue into the deepest portions of the data, which is coincident with the projected depth to bedrock beneath the field station and is interpreted to be an undersaturated zone within the fractured Oswego Sandstone; and 4) low resistivities below an elevation of - 190 ft are interpreted to be the top of the saturated domain within the fractured bedrock.