DIPOLE-DIPOLE ELECTRICAL RESISTIVITY CHARACTERIZATION OF THE LYCOMING VALLEY GLACIAL AQUIFER LYCOMING COUNTY, PA

The Lycoming Creek Valley is located in northern Lycoming County, PA within the glaciated Appalachian Plateau. The steep valleys walls are blanketed with a thin veneer of colluvium that overlies the Devonian aged Catskill sandstone that abruptly terminates as a flat bottom 300-500 meters in width. Little is known about the surficial deposits comprising the valley fill, although multiple stream terraces along the valley flanks and limited exposures of inversely graded boulder-gravel suggest a complex geologic history. Dipole-Dipole resistivity surveys were collected in an attempt to determine the depth of the valley fill and character of the unconfined aquifer.

Cross-valley profiles were completed at ~3 kilometer intervals. Surveys were completed with either a 3-meter spacing or a 5-meter electrode spacing depending on accessibility and the narrow width valley. Surveys were completed using a Wenner muti-electrode array. Subsurface features exist in three distinct zones, which are consistent in all survey lines. The geoelectric sections clearly delineate a 1.5-to-3 meter thick high resistivity zone interpreted as the vadose zone. An abrupt decrease in resistivity indicates contact with the water table at a depth of 4 meters. The saturated zone consistently extended straight downward to bedrock with an inferred bedrock interface consistently occurring at a depth of 20-22 meters. One geoelectric section intersected a low resistive/ highly conductive body running down valley, which may indicate the narrow coarse-grained glacial aquifer may be especially vulnerable to contamination. The coarse-grained aquifers comprising this valley and several others most likely represent a major recharge flow path to the Susquehanna River Basin.