HR: 1340h
AN: H23A-1121    [Abstracts]
TI: Using High-Resolution Seismic Reflection Techniques to Image Sand Channels Within the Potomac Aquifer System in New Castle County, Delaware
AU: * Costas, E M
EM: percyon@udel.edu
AF: Department of Geology, University of Delaware, Newark, DE 19716 United States
AU: McGeary, S
EM: smcgeary@udel.edu
AF: Department of Geology, University of Delaware, Newark, DE 19716 United States
AU: McKenna, T E
EM: mckennat@udel.edu
AF: Delaware Geological Survey, University of Delaware, Newark, DE 19716 United States
AU: McLaughlin, P P
EM: ppmclau@udel.edu
AF: Delaware Geological Survey, University of Delaware, Newark, DE 19716 United States
AB: Preliminary results are presented from an ongoing project designed to use high-resolution seismic reflection imaging methods to examine the stratigraphy of the Potomac aquifer system in Delaware. The Potomac Formation is a heterogeneous, non-marine, Cretaceous unit that includes important fresh water aquifers. This study aims to use seismic reflection data to characterize the sand bodies that are woven though a section predominantly composed of silts and clays. The sands are believed to be paleo-river channels, whereas the silts and clays are overbank deposits. The seismic reflection data will provide the geometrical characteristics of the sand channels, which can provide important constraints for groundwater modeling or contaminant transportation studies in the Potomac aquifer system. We are currently conducting the seismic reflection survey using a 24-channel Geometrics Strataview seismograph and a sledgehammer source. Three profiles covering a total of 1.6 kilometers have been collected to date. These seismic lines were collected using a geophone and shot spacing of 5 meters and a source offset of 30 meters. The data were collected on farms located immediately south of the Chesapeake and Delaware Canal in a region of open land area where Potomac sand channels are likely. After preliminary processing, reflections in the data can be seen as deep as 350 ms, which is possibly basement. Most coherent reflections are above 300 ms. Strong reflections correlate between profiles at both 185-200 ms and 240-260 ms, which are possible sand bodies within the Potomac aquifer system. These reflections are generally continuous, with some lateral variation. Frequency content is reasonably high, up to about 200 Hz. Continuing work will include additional lines within the study area allowing for improved delineation of the lateral extent and stratigraphic relationships of the channel intervals in three dimensions.
DE: 0900 EXPLORATION GEOPHYSICS
DE: 0935 Seismic methods (3025)
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting