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.

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. 17 (Harbeson quadrangle). The complex geologic history of the surficial units of the Harbeson Quadrangle 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 is further complicated by periglacial activity that produced dune deposits and Carolina Bays scattered throughout the map area.

The complex geologic history of the surficial units of the Harbeson Quadrangle is one of deposition of the Beaverdam Formation and its subsequent modification by erosion and deposition related to sea-level fluctuations during the Pleistocene. The geology is further complicated by periglacial activity that produced dune deposits and Carolina Bays scattered throughout the map area.

This vector data set contains the rock unit polygons for the surficial geology in the Delaware Coastal Plain covered by DGS Geologic Map No. 16 (Fairmount and Rehoboth Beach quadrangles). The geologic history of the surficial units of the Fairmount and Rehoboth Beach 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 both onshore, in Rehoboth Bay, and offshore. Erosion during the late Pleistocene sea-level low stand and ongoing deposition offshore and in Rehoboth Bay during the Holocene rise in sea level represent the last of several cycles of erosion and deposition.

To facilitate the GIS community of Delaware and to release the geologic map of the Fairmount and Rehoboth Beach quadrangles with all cartographic elements (including geologic symbology, text, etc.) in a form usable in a GIS, we have released this digital coverage of DGS Geological Map 16. The update of earlier work and mapping of new units is important not only to geologists, but also to hydrologists who wish to understand the distribution of water resources, to engineers who need bedrock information during construction of roads and buildings, to government officials and agencies who are planning for residential and commercial growth, and to citizens who are curious about the bedrock under their homes. Formal names are assigned to all rock units according to the guidelines of the 1983 North American Stratigraphic Code (NACSN, 1983).

The geologic history of the surficial units of the Fairmount and Rehoboth Beach 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 both onshore, in Rehoboth Bay, and offshore. Erosion during the late Pleistocene sea-level low stand and ongoing deposition offshore and in Rehoboth Bay during the Holocene rise in sea level represent the last of several cycles of erosion and deposition.

This vector data set contains the rock unit polygons for the surficial geology in the Delaware Coastal Plain covered by DGS Geologic Map No. 15 (Geologic Map of the Georgetown Quadrangle, Delaware). The geologic history of the surficial geologic units of the Georgetown Quadrangle is primarily that of deposition of the Beaverdam Formation and its subsequent modification by erosion and deposition of younger stratigraphic units. The age of the Beaverdam Formation is uncertain due to the lack of age-definitive fossils within the unit but is thought to be between late Pliocene to early Pleistocene in age. Refer to Ramsey, 2010 (DGS Report of Investigations No. 76) for details regarding the stratigraphic units.

To facilitate the GIS community of Delaware and to release the geologic map of the Georgetown Quadrangle with all cartographic elements (including geologic symbology, text, etc.) in a form usable in a GIS, we have released this digital coverage of DGS Geological Map 15. The update of earlier work and mapping of new units is important not only to geologists, but also to hydrologists who wish to understand the distribution of water resources, to engineers who need bedrock information during construction of roads and buildings, to government officials and agencies who are planning for residential and commercial growth, and to citizens who are curious about the bedrock under their homes. Formal names are assigned to all rock units according to the guidelines of the 1983 North American Stratigraphic Code (NACSN, 1983).

The geologic history of the surficial geologic units of the Georgetown Quadrangle is primarily that of deposition of the Beaverdam Formation and its subsequent modification by erosion and deposition of younger stratigraphic units. The age of the Beaverdam Formation is uncertain due to the lack of age-definitive fossils within the unit. Stratigraphic relationships in Delaware indicate that it is no older than late Miocene and no younger than early Pleistocene. Regional correlations based on similarities of depositional style, stratigraphic position, and sediment textures suggest that it is likely late Pliocene in age; correlative with the Bacons Castle Formation of Virginia (Ramsey, 1992, 2010).

This map shows the surficial geology of Kent 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 flood-prone areas, to identify sand and gravel resources, and to support state, county, and local land-use and planning decisions.

The surficial geology of the Ellendale and Milton quadrangles reflects the geologic history of the Delaware Bay estuary and successive high and low sea levels during the Quaternary. Ramsey (1992) interpreted the Beaverdam Formation as deposits of a fluvial-estuarine system during the Pliocene. Sediment supply was high, in part due to geomorphic adjustments in the Appalachians related to the first major Northern Hemisphere glaciations around 2.4 million years ago. The Beaverdam Formation forms the core of the central Delmarva Peninsula around which wrap the Quaternary deposits.

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.

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.

These vector and raster data sets contain the rock unit polygons for the surficial geology in the Delaware Coastal Plain covered by DGS Geologic Map No. 11 (Milton-Ellendale area) in ESRI shapefile and TIF format.

This data set contains the rock unit polygons for the surficial geology in ESRI shapefile format for DGS Geologic Map No. 14 (Geologic Map of Kent County, Delaware). This map shows the surficial geology of Kent County, Delaware, at a scale of 1:100,000.