32 Hydrogeology and Environmental Geology (Posters)

Wednesday, 16 March 2005
8:00 AM - 12:00 PM

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

Paper number: 32-16
Program: Technical Sessions
Time: 8:00 AM – 12:00 PM

Authors

Abstract

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.