Abstract: Environmental Subsurface Mapping Using Shallow High Resolution Reflective Seismic in the Upper Coastal Plain of South Carolina

M. C. Waddell, D. E. Wyatt, F. Keith, R.A. Aadland

Subsurface geologic mapping for environmental assessment often requires an integrated approach. Generally, environmental site assessments consist of drilling and coring wells and mapping the subsurface by correlating between the drill holes. This paper presents case studies combining shallow high resolution and very high resolution seismic reflection profiling in unconsolidated sediments with borehole and well data to map the subsurface geology of the South Carolina Coastal Plain. At selected sites, structural interpretations that may affect groundwater and contaminant transport are demonstrated using 2-D and 3-D shallow seismic. Using the 2-D high resolution seismic for stratigraphic sequence interpretations, it is possible to delineate the different hydrostratigraphic units. Using b th 2-D and 3-D seismic, faults and folds inferred from borehole data were confirmed with the seismic data. In other areas, seismic data enabled the mapping of faults that had gone unrecognized from borehole data nor were suspected from regional geological mapping.

The quality of the high resolution seismic data provides an opportunity to interpret and map sediment sequences that control hydrostratigraphic relationships. Small-scale sequence packages such as erosional channels as well as other unconformable events can be mapped to aid in comprehensive groundwater assessment. These techniques are familiar to most petroleum geologists and are proving to have valuable applications in the field of environmental assessment studies.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994