This resource is a compilation of the Geologic Units of Delaware, provided by the Delaware Geological Survey and made available for distribution through the AASG Geothermal Data Systems project, published as a web feature and available as an Excel workbook for download. The workbook contains 7 worksheets, including information about the template, notes related to revisions of the template, Resource provider information, the data, a field list (data mapping view) and vocabularies used to populate the data worksheet (data valid terms). Data from 54 geologic units are included. Fields in the data table include unit names, descriptions, symbols/labels, lithology and data source.
Report of Investigations detailing the history of oil and gas exploration in the mid-Atlantic and Delaware's involvement in the OCS leasing program
Bulletin describing stratigraphy of Delaware, for more information on this resource please see links provided.
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 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. The map was compiled from topographic and geologic maps, aerial photographs, geologists' and drillers' logs, geophysical logs, soils maps, and sample descriptions. Samples from drill holes and outcrops were examined for comparison with previous descriptions. Other than the Old College (Ramsey, 2005) and Bridgeton Formations (Owens, 1999; Owens et al., 1970), all geologic units were previously mapped or described in Delaware. Descriptions of geologic units, unless otherwise referenced, were generated by the author after examination of cores, outcrops, and samples from the Delaware Geological Survey Core and Sample Repository.
Progress report on the geothermal potential for the state of Delaware by examining five Department of Energy 1,000 foot test wells
Report of Investigation detailing the analysis and summary of water-table maps for the Delaware Coastal Plain
Publication prepared to serve as a general procedure guide to various technical, economic, and institutional aspects of geothermal development in Delaware
Report of investigations on the Cat Hill Formation and the Bethany Formation of Delaware and their importance of ground water to the local areas
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.
Open file report on the subsurface geology and resource potential, focusing on the hydrocarbon, of southern Delaware for the nontechnical reader. This review summarizes the present knowledge of the subsurface
geology and resource potential of southern Delaware and outlines the needs for future studies to gain further understanding of these matters. Because of the present interest in exploring for oil and gas beneath the Atlantic Outer Continental Shelf it is most timely that the primary resource considered in this report be the hydrocarbon (petroleum and natural gas) potential of the State. Hydrocarbons occur in commercial quantities only in thick sections of sedimentary rock, therefore, southern Delaware (primarily Sussex County) is the focus of this study because the thickest sedimentary rock section in the State is here. Assessment of the hydrocarbon potential of this area also has bearing on other resources such as groundwater (both fresh water and subsurface brines), underground storage of natural gas, and underground waste disposal.
This data set contains 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 format. The original Geologic Map Description of the published map follows: 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 North 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. The Columbia Formation which is recognized to the north of the map area was deposited as the result of the distal portion of glacial outwash of the Delaware and possibly Susquehanna rivers during the early Pleistocene (Ramsey, 1997). After the deposition of the Columbia, the Delaware River and Bay developed their present geographic positions. In the northwest portion of the map area contiguous with the area mapped by Ramsey (1993) as the Columbia Formation, the surficial unit has many similarities in texture, color, bedding, geophysical log character, and thickness with the Beaverdam Formation to the south and east. No diagnostic pollen-bearing beds or other fossils have been found in the area to aid in identification of the unit. Because of the continuity in thickness and lithic character with the Beaverdam, the area in mapped as Tbd?. Where the Beaverdam is mapped, silty clay to clayey silt beds yielded pollen assemblages characteristic of the unit (Andres and Ramsey, 1995, 1996; Groot and Jordan, 1999). The Lynch Heights and Scotts Corners formations (Ramsey, 1993, 1997) represent shoreline and estuarine deposits associated with high stands of sea level during the middle to late Pleistocene on the margins of Delaware Bay. The western boundary of these units is found at a topographic break (scarp) that marks the ancestral, erosional shoreline of Delaware Bay during the sea-level high stand. Upland dunes (Qd) are extensive linear dunes and large dune fields found along the contact between the Lynch Heights and older deposits to the west. Some of these dunes may be relict coastal dunes associated with the ancestral shoreline of Delaware Bay at the time of Lynch Heights deposition. Dunes to the west may be younger; late Pleistocene or early Holocene in age. Carolina Bay deposits are circular to semi-circular depressions with sand rims found in the northern half of the Milton Quadrangle. They are thought to be cold climate features associated with reduced tree cover and increased winds during the glacial periods of the Pleistocene (Ramsey, 1997). Quaternary upland deposits (Qud) cover much of the southern half of the Ellendale Quadrangle. These deposits represent deposition in swamps associated with poor drainage and eolian deposition during cold climate phase of the late Pleistocene and early Holocene. The eolian sands are found both as small dunes in this area, but more commonly, as sheets of fine to medium sand with no to rare sedimentary structures. Although no radiocarbon dates have been collected from this area, the age of the deposits is considered to be latest Pleistocene to early Holocene on the bases of similarities in stratigraphic position and depositional style with the Cypress Swamp Formation (Andres and Howard, 2000) found to the south of the map area. Quaternary and older deposits are transgressed by Holocene swamp, marsh, shoreline, and estuarine deposits along the stream valleys and shoreline of Delaware Bay. Stratigraphic units found at depth within the map area are shown with the geophysical log of Ng42-17, a deep test well drilled in Milton. Major aquifer units are also shown. Cross section A-A' is a north-south section roughly along Route 113 through the center of the Ellendale Quadrangle. It shows the relationship of the Beaverdam Formation (Tbd?) and the Beaverdam Formation (Tbd). Also shown are the units underlying the surficial units and position of the major aquifers. Cross-section B-B' is a west-east section showing the relationships between the Quaternary-Tertiary deposits undifferentiated, Lynch Heights, and Scotts Corners formations as well as underlying stratigraphic units. Aquifers shown in the cross-sections are water-bearing sand layers that are used for public, domestic, agricultural, and industrial sources of water. Where the surficial or water-table aquifer is in contact with sands of an underlying geologic unit such as the Manokin formation, the entire water-bearing unit is called the Columbia aquifer.
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 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. The map was compiled from topographic and geologic maps, aerial photographs, geologists' and drillers' logs, geophysical logs, soils maps, and sample descriptions. Samples from drill holes and outcrops were examined for comparison with previous descriptions. Descriptions of geologic units, unless otherwise referenced, were generated by the author after examination of cores, outcrops, and samples from the Delaware Geological Survey Core and Sample Repository.
The vector data set contains the rock unit polygons for the surficial geology for DGS Geologic Map No. 10. The original Geologic Map Description of the published map follows: This map is 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. This map is available in both analog and digital formats from the Delaware Geological Survey (DGS) website; data on individual rock types can be found in the DGS Data Repository on the DGS web site. The map incorporates much of the previous work done in the Piedmont (Bascom et al., 1909; Bascom and Miller, 1920; Bascom and Stose, 1932; Ward, 1959; Woodruff and Thompson, 1972, 1975; Higgins et al. 1973; Crawford and Crawford, 1980; Crawford and Mark, 1982; Wagner and Srogi, 1987; Srogi, 1988; Alcock, 1994; Woodruff and Plank, 1995; and Plank and Schenck, 1997). The map includes the adjacent Pennsylvania Piedmont to show the entire extent of the Mill Creek Nappe and the Arden Pluton. We were aided in mapping the geology around the Landenberg and Avondale anticlines by J. E. Alcock (personal communication, 2000). The amphibolites in Pennsylvania are as mapped in the Pennsylvania Geologic Atlas (Berg and Dodge, 1981). We have attempted to show the larger amphibolite bodies within the Wissahickon Formation in Delaware. Schenck (1997) gives a detailed history of previous geologic work in the Piedmont of Delaware and adjacent Maryland and Pennsylvania. Our model for the geologic history of the Delaware Piedmont is one of eastward dipping subduction and closure of a forearc basin bringing magmatic arc crust over forearc basin sediments, nearshore deposits, and continental crust during the Taconic orogeny. The metaigneous, metavolcanic, and igneous rocks of the Wilmington Complex represent the magmatic arc, the metasedimentary rocks of the Wissahickon Formation represent forearc sediments, and the rocks of the Glenarm Group and Baltimore Gneiss represent Paleozoic nearshore deposits and continental crust of Grenville-age, respectively. Although penetrative deformation and upper amphibolite to granulite facies metamorphism have obscured most igneous fabrics and contact relationships in the Wilmington Complex, we consider the Brandywine Blue Gneiss, Barley Mill Gneiss, Montchanin Metagabbro, Mill Creek Metagabbro, and Christiansted Gneiss as metamorphosed plutonic rocks, and the Rockford Park Gneiss, Faulkland Gneiss, and Windy Hills Gneiss as metamorphosed volcanic and volcaniclastic rocks. U-Pb ages of igneous crystallization of zircon for these 8 units within the Wilmington Complex range between 488 and 470 Ma. (John N. Aleinikoff, U. S. Geological Survey, personal communication, 2000). The Arden composite pluton, Bringhurst Gabbro, and Iron Hill Gabbro are probably younger than the other units in the Wilmington Complex because igneous fabrics are preserved, and U-Pb dates on the igneous zircons in the Arden composite pluton are reported to be 422+/-6.5 Ma. (Bosbyshell et al., 1998) and 434+/-4 Ma (John N. Aleinikoff, U. S. Geological Survey, personal communication, 2000). Trace elements in the mafic rocks of the Arden composite pluton indicate the mafic rocks are similar to E-MORBS or back arc basin basalts (Plank et al., in press), thus they probably intruded during a late-stage rifting event within the arc. The metasedimentary rocks and amphibolites of the Wissahickon Formation were deposited in a forearc basin. Geochemistry of the amphibolites indicates they were derived from a variety of magma sources (R. C. Smith and J. H. Barnes,1994; Pennsylvania Geological Survey, unpublished reports). One type of amphibolite is enriched in Fe and Ti and has trace element compositions similar to intraplate basalts suggesting the magma formed seamounts within the forearc basin. Another type of amphibolite has trace element compositions similar to MORBs and E-MORBs. This magma either erupted during rifting within the forearc basin or was preserved in the basin as a remnant of oceanic crust. Metamorphism in the Delaware and adjacent southeastern tern Pennsylvania Piedmont varies from amphibolite to granulite grade. The highest grade of metamorphism is recorded in the Brandywine Blue Gneiss and the Rockford Park Gneiss in Delaware with the intensity of metamorphism decreasing from there in all directions (Wycoff, 1952; Crawford and Mark, 1982; Wagner and Srogi, 1987; Alcock, 1989; Plank, 1989; Schenck and Plank, 1995; Alcock and Wagner, 1995; Bosbyshell et al., 1999). The decrease has also been noted within the Brandywine Blue Gneiss and the Rockford Park Gneiss where granulite gneiss in the city of Wilmington and east of Concord Pike changes to amphibolite grade gneiss to the north in Pennsylvania (Ward, 1959). The interfingering of Wissahickon metasediments with Wilmington Complex volcanic and volcaniclastic rocks plus the identification of a small dike of Rockford Park Gneiss that intrudes the Wissahickon Formation in Glens Mills, Pennsylvania (Bosbyshell et al., 1999), suggests that the Wissahickon Formation and Wilmington Complex came into contact early in history of the arc. Isotopic evidence based on metamorphic zircons in the Brandywine Blue Gneiss constrains the high grade metamorphism to 441 Ma. (Grauert and Wagner, 1975; Wagner and Srogi, 1987) and 432+/-6 Ma (John N. Aleinikoff, U. S. Geological Survey, personal communication, 2000). The metamorphic ages are similar to the igneous ages of the younger plutons that intruded during the rifting event at about 422 Ma and 432 Ma and indicate that the granulite metamorphism was associated with high heat flow developed during arc rifting. Previous studies have modeled the thrust emplacement of the Wissahickon Formation and the folding and thrusting of the Mill Creek Nappe as events that occurred during northwest directed Taconic compression. These events probably represent a continuum beginning with the deformation of the Baltimore Gneiss, the Glenarm units, and the Wissahickon Formation. As subduction closed the forearc basin between the magmatic arc and ancient continent, Wissahickon sediments were thrust over developing nappes in the Baltimore Gneiss and its Glenarm cover. Folding continued, and this initial thrust contact was also folded. In a final compressional event, a thrust developed that cut the first thrust and brought the Baltimore Gneiss and Glenarm Group over Wissahickon to the northwest (Alcock, 1989, 1991, and 1994; Woodruff and Plank, 1995; Plank and Schenck, 1997).
This resource is a compilation of heat flow observations compiled by the Virginia Tech Geothermal Program, published as a Web feature service for the National Geothermal Data System by the Delaware Geological Survey. This is the most current dataset and uses schema version 1.23. The data are available in the following formats: web feature service, web map service, ESRI service endpoint, and an Excel workbook for download. The workbook contains 5 worksheets, including information about the template, notes related to revisions of the template, resource provider information, the data, a field list (data mapping view) and vocabularies (data valid terms) used to populate the data worksheet. This resource was provided by the Delaware Geological Survey and made available for distribution through the National Geothermal Data Systems project.
The Michigan Geological Survey NGDS node is a Geoportal catalog serving geothermal-relevant resources for the state of Michigan.