This vector data set contains the rock unit polygons for the surficial geology in the Delaware Coastal Plain covered by DGS Geologic Map Series No. 18 (Bethany Beach and Assawoman Bay Quadrangles). The geologic history of the surficial units of the Bethany Beach and Assawoman Bay Quadrangles is that of deposition of the Beaverdam Formation and its subsequent modification by erosion and deposition related to sea-level fluctuations during the Pleistocene. The geology reflects this complex history onshore, in Indian River Bay and Assawoman Bay, and offshore in the Atlantic Ocean. Erosion during the late Pleistocene sea-level lowstand and ongoing deposition offshore and in Indian River Bay during the Holocene rise in sea level represents the latest of several cycles of erosion and deposition. An additional dataset of datapoints used to generate rock unit polygons for the surficial geology in the Delaware Coastal Plain covered by DGS Geologic Map Series No. 18 (Bethany Beach and Assawoman Bay quadrangles) exists for use in conjunction with this dataset.

The geologic history of the surficial units of the Bethany Beach and Assawoman Bay Quadrangles is that of deposition of the Beaverdam Formation and its subsequent modification by erosion and deposition related to sea-level fluctuations during the Pleistocene. The geology reflects this complex history onshore, in Indian River Bay and Assawoman Bay, and offshore in the Atlantic Ocean. Erosion during the late Pleistocene sea-level lowstand and ongoing deposition offshore and in Indian River Bay during the Holocene rise in sea level represents the latest of several cycles of erosion and deposition.

Southern New Castle County is dependent on ground water for nearly all of its water supply. The area has been undergoing development from predominately agricultural land use to urban/suburban land use (Delaware Water Supply Coordinating Council [WSCC], 2006). With this development comes a need to more accurately predict the availability of ground water to reduce the potential of overusing the resource. This report has 3 plates listed as separate files.

This map is the first detailed surficial geologic map in southern Kent and northern Sussex counties. Other maps covering the same or adjacent areas have focused on subsurface geology (Benson and Pickett, 1986), hydrogeology (Talley, 1982), or surficial geology on a regional basis (Jordan, 1964; Owens and Denny, 1979; Ramsey and Schenck, 1990). The purpose of this map is to show the distribution of geologic units found at or near the present land surface. These units are composed of the geologic materials that support agriculture and development, are mined for sand and gravel resources, and are the surface-to-subsurface pathway for water.

Subsurface geology of the southern central portion of Kent County.

The scanned raster and vector datasets contains the rock unit polygons for the surficial geology for DGS Geologic Map No. 8 (Milford-Mispillion River Quadrangles). This map is the first detailed surficial geologic map in southern Kent and northern Sussex counties.