Delaware’s oldest rocks are metamorphic crystalline rocks of the central Appalachian Piedmont Physiographic Province. Atlantic Coastal Plain sediments overlie the crystalline rocks of the Piedmont and range in thickness from a feather edge at the Fall Line to approximately 9,000 feet in the southeastern corner of Delaware. Sediments range in age from Early Cretaceous to Holocene.
The feasibility of using geophysical techniques in determining the amount of overburden and the nature of the subsurface along a proposed highway was tested in the Piedmont area of Delaware. The area is underlain by crystalline rocks capped by varying amounts of unconsolidated material or regolith. Seismic refraction and surface resistivity methods were used at selected stations and the interpretations were later compared to results from test holes and to the material exposed in road cuts. In general, interpretation of the seismic refraction results compared quite well with test borings and with field observations made after construction was started. Resistivity data were inconclusive in themselves but provided some additional control points when correlated with seismic refraction data. With proper control, it is concluded that such techniques could be useful in the Piedmont of Delaware for highway planning.
The ground-water recharge potential map of Kent County, Delaware, is a compilation of 1:24,000-scale maps of the water-transmitting properties of sediments in the interval between land surface and 20 ft below land surface. Water-transmitting properties are a key factor in determining the amount of water that recharges Delaware’s aquifers and the susceptibility of aquifers used as sources of water supply to contamination from near-surface pollutant sources. The mapping methodology was developed by Andres (1991) for the geologic characteristics of the Atlantic Coastal Plain portion of Delaware. Mapping and methods development started in 1990 and the final maps were completed in 2002 (Andres et al., 2002). Additional information about the map and methodology and a list of cited references are presented on the reverse side. The mapping program was funded by the Delaware Department of Natural Resources and Environmental Control and the Delaware Geological Survey.
Geology and hydrology of the Chesapeake and Delaware Canal Area, Delaware. There are 2 sheets in this series.