Additional sources of ground water have been located in the Piedmont Province as a result of a ground-water exploration program conducted by the Delaware Geological Survey at the University of Delaware in cooperation with the City of Newark. Drilling sites for relatively high-yielding wells were located through the use of geophysical investigations, air-photo interpretation, field mapping, and review of existing data.

The complex geologic framework of the Fall Zone in Delaware is primarily caused by diverse structural features present in the crystalline basement rocks that have exerted a considerable influence on the distribution of the overlying sediments of the Coastal Plain.

The results of an intensive ground-water study on University of Delaware lands in the Newark area revealed additional sources of available ground water. Geophysical techniques, air-photo interpretation, studies of existing data, field mapping, test drilling, and pump tests were used as the bases for guiding additional well development. The study, conducted by the Delaware Geological Survey, was a cooperative effort between the University of Delaware and the City of Newark in response to mutual water supply problems. A potential ground-water yield of about 500 gpm was discovered on the University Laird Tract in the Piedmont Province. Ground water available from other locations in the Coastal Plain portion of the study area may total about 175 gpm. However, careful well development and proper well spacing will be necessary to obtain optimum yields.

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.

Geology and Hydrology of the Newark, Delaware area. There are 2 sheets in this series.

This map shows the surficial geology of New Castle County, Delaware at a scale of 1:100,000. Maps at this scale are useful for viewing the general geologic framework on a county-wide basis, determining the geology of watersheds, and recognizing the relationship of geology to regional or county-wide environmental or land-use issues. This map, when combined with the subsurface geologic information, provides a basis for locating water supplies, mapping ground-water recharge areas, and protecting ground and surface water. Geologic maps are also used to identify geologic hazards, such as sinkholes and flood-prone areas, to identify sand and gravel resources, and for supporting state, county, and local land-use and planning decisions.

This is a map of the crystalline bedrock units in the Piedmont of Delaware and adjacent Pennsylvania. The southern boundary of the mapped area is the updip limit of the Potomac Formation (Woodruff and Thompson, 1972, 1975). Soil, regolith, and surficial deposits of Quaternary age are not shown.

Crystalline bedrock geology of the Newark area, Delaware.

This dataset contains the geologic polygons used for the creation of DGS Geologic Map 13. This dataset shows the surficial geology of New Castle County, Delaware, at a scale of 1:100,000.