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ItemBasic Data For The Geologic Map Of The Seaford Area, Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 1995) Andres, A.S.; Ramsey, K.W.; Schenck, W.S.The Seaford area geologic mapping project (Andres and Ramsey, 1995) was conducted by Delaware Geological Survey (DGS) staff and focused on the Seaford East (SEE) and Delaware portion of the Seaford West (SEW) quadrangles (Fig. 1). Data evaluated in support of mapping from these quadrangles and surrounding areas are documented in this report. ItemBeach Sand Textures From The Atlantic Coast Of Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 1999) Ramsey, K.W.The purpose of this report is to characterize Delaware Atlantic Coast beach sand on the basis of sand texture data in order to identify geologic material suitable for beach nourishment. ItemBedrock Geologic Map of the Delaware Piedmont(Newark, DE: Delaware Geological Survey, University of Delaware, 2021-06) Schenck, W.S.The Piedmont rock units in Delaware, and bedrock geologic map of Schenck et al. (2000) are revised in this report based on new rock geochemistry, geochronometric data, petrography, and recent detailed mapping. Major revisions include: • revising the extent of the Christianstead Gneiss and Windy Hills Gneiss • abandoning the Wissahickon Formation as originally mapped in Delaware by Bascom (1902, 1905) and Bascom et al. (1909, 1920, and 1932) and replacing it with the Mt. Cuba Gneiss, a lithodeme of the West Grove Metamorphic Suite (Bosbyshell et al., 2012, 2013, 2014, 2015), and reserving the Wissahickon Schist/Formation for the metasediments on the east side of the Wilmington Complex magmatic arc and referring to them herein as Wissahickon Formation (restricted sense) • extending the Rosemont Shear Zone from Pennsylvania southwest through Delaware to Maryland separating the Mt. Cuba Gneiss and the Wilmington Complex • formally naming and describing two new units in the Wilmington Complex - the Greenville Gabbro and the Thompsons Bridge Gneiss. Additional Notes Plate 1 of OFR54 can also be viewed in a Web Mapping Application. Layers can be turned on and off and manipulated under the "Layers" icon in the upper right hand corner. Cross section is available by clicking on the cross section line. Rock unit descriptions available by clicking on the geologic map. OFR54 Plate 1 (Bedrock Geologic Map of the Delaware Piedmont) Web Mapping Application Plate 1 Summary The vector data set contains the rock unit polygons for the surficial geology for DGS Open File Report 54 - Plate 1. The Piedmont rock units in Delaware, and bedrock geologic map of Schenck et al. (2000) are revised on this map based on new rock geochemistry, geochronometric data, petrography, and recent detailed mapping. Major revisions include: • revising the extent of the Christianstead Gneiss and Windy Hills Gneiss • abandoning the Wissahickon Formation as originally mapped in Delaware by Bascom (1902, 1905) and Bascom et al. (1909, 1920, and 1932) and replacing it with the Mt. Cuba Gneiss, a lithodeme of the West Grove Metamorphic Suite (Bosbyshell et al., 2012, 2013, 2014, 2015), and reserving the Wissahickon Schist/Formation for the metasediments on the east side of the Wilmington Complex magmatic arc and referring to them herein as Wissahickon Formation (restricted sense) • extending the Rosemont Shear Zone from Pennsylvania southwest through Delaware to Maryland separating the Mt. Cuba Gneiss and the Wilmington Complex • formally naming and describing two new units in the Wilmington Complex - the Greenville Gabbro and the Thompsons Bridge Gneiss. ItemCatalog Of Earthquakes In Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 2000) Baxter, S.J.The occurrences of earthquakes in northern Delaware and adjacent areas of Pennsylvania, Maryland, and New Jersey are well documented by both historical and instrumental records. Over 550 earthquakes have been documented within 150 miles of Delaware since 1677. One of the earliest known events occurred in 1737 and was felt in Philadelphia and surrounding areas. The largest known event in Delaware occurred in the Wilmington area in 1871 with an intensity of VII (Modified Mercalli Scale). The second largest event occurred in the Delaware area in 1973 (magnitude 3.8 and maximum Modified Mercalli Intensity of V-VI). The epicenter for this event was placed in or near the Delaware River. Sixty-nine earthquakes have been documented or suspected in Delaware since 1871. ItemCharacterization Of The Potomac Aquifer, An Extremely Heterogeneous Fluvial System In The Atlantic Coastal Plain Of Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 2004) McKenna, T.E.; McLaughlin, P.P.; Benson, R.N.Fluvial sands of the subsurface Cretaceous Potomac Formation form a major aquifer system used by a growing population in the northern Coastal Plain of Delaware. The aquifer is extremely heterogeneous on the megascopic scale and connectivity of permeable fluvial units is poorly constrained. The formation is characterized by alluvial plain facies in the updip section where it contains potable water. While over 50 aquifer tests indicate high permeability, the formation is primarily composed of fine-grained silt and clay in overbank and interfluvial facies. Individual fluvial sand bodies are laterally discontinuous and larger-scale sand packages appear to be variable in areal extent resulting in a labyrinth style of heterogeneity. The subsurface distribution of aquifers and aquitards has been interpreted within a new stratigraphic framework based on geophysical logs and on palynological criteria from four cored wells. The strata dip gently to the southeast, with generally sandy fluvial facies at the base of the formation lapping onto a south-dipping basement unconformity. The top of the formation is marked by an erosional unconformity that truncates successively older Potomac strata updip. Younger Cretaceous units overly the formation in its downdip area. In the updip area, the formation crops out or subcrops under Quaternary sands.The fine-grained facies include abundant paleosols that contain siderite nodules and striking mottling that commonly follows ped faces and root traces. These paleosols may serve as regional aquitards. This geologic complexity poses a challenge for determining the magnitudes and directions of ground-water flow within the aquifer that are needed for making informed decisions when managing this resource for water supply and contaminant remediation. ItemConfiguration Of The Base And Thickness Of The Unconfined Aquifer In Southeastern Sussex County, Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 1983-05) Denver, J.M.The purpose of this study was to map the thickness and the configuration of the base of the unconfined aquifer in southeastern Sussex County, Delaware (figure 1). The unconfined aquifer provides much of the water used in this part of the State and is the first unit to be affected by pollution or waste disposal problems. Contour maps and geologic sections were prepared from available geologic, geophysical, and drillers' logs and previously published reports and maps. Six test holes (figure 1) were drilled to supplement available data. The information in this report will be useful for water-resources planning and for locating water-supply wells in the unconfined aquifer. ItemData Report On Rock Cores From Red Mill Road, Harmony Road, Prices Corner, And Newport, Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 1995-06) Schenck, W.S.; Plank, M.O.The Delaware Piedmont is underlain by metamorphosed sedimentary and igneous rocks of Middle Proterozoic to Paleozoic age. The rocks have been studied for many years, but because of poor exposure, high-grade metamorphism, and intense deformation, it has been difficult to identify units, understand their stratigraphic relationships to one another, and determine their origin and history; however, northern Delaware occupies a critical position in the central Appalachian Piedmont, and understanding its geology is key to understanding the geology of this region. ItemDatabase of Quaternary Coastal Geochronologic Information for the Atlantic and Pacific Coasts of North America (additional information for sites in Peru and Chile)(Newark, DE: Delaware Geological Survey, University of Delaware, 2015-02) Wehmiller, John F.; Pellerito, V.Open-File Report 50 presents and describes a database of geochronological information for coastal deposits of the US Atlantic and Pacific coasts, as well as for sites from the Pacific coast of South America. This database represents a synthesis of nearly forty years of study conducted by John F. Wehmiller and students in the Department of Geological Sciences, University of Delaware, as well as many collaborating colleagues. The majority of the chronological information in the database is based on amino acid racemization (AAR) data for fossil mollusks obtained from over 1000 collection sites. These chronological data have been used for various mapping, paleoenvironmental, stratigraphic, sea-level, and tectonic studies. In addition to the database itself, 18 on-line supplements containing information related to sample descriptions, sample and collection site photographs, field notes, supporting or related analytical data, and laboratory publications and technical reports are available. Periodic updates and additions will be made where appropriate. The database will be updated regularly to add new data or to complete entries that are currently blank. The instructions provided with the database indicate the date of the latest revision, as well as all revisions after the first release. Some output data from the Amino Acid Racemization Data Base (AARDB) are available at on-line mapping sites or are posted to the NOAA-World Data Center for archival preservation (http://www.ncdc.noaa.gov/paleo/aar.html). ItemDelaware Geological Survey Petrographic Data Viewer(Newark, DE: Delaware Geological Survey, University of Delaware, 2021-05) Schenck, W.S.; Wang, L.T.Petrography is a branch of geoscience focused on the description and classification of rocks, primarily by microscopic study of optical properties of minerals. A thin sliver of rock is cut from a sample, mounted on a glass slide, ground to approximately 30 microns (0.03mm), and viewed under a microscope that uses polarized light. By observing the colors produced as plain polarized light and crossed (90 degrees) polarized light shines through the minerals, petrologists can determine the minerals that comprise the sampled rock. The data and photomicrographs of thin sections within the Delaware Geological Survey (DGS) Petrographic Data Viewer represent the total collection of the Delaware Geological Survey for the Delaware Piedmont and surrounding areas. The data viewer includes slides from DGS research, slides donated by researchers, and slides culled from class reports, master's theses, and Ph.D. dissertations. Within the application, the “Slide Made For” field identifies the original owner of the thin section. The researchers include: John Branca, A.D. Cohen, Bernard Dirska, Gregory S. Ghon, G. Michael Hager, C. Scott Howard, Guy W. Metz, Margaret O. Plank, LeAnn Srogi, Richard F. Ward, and DGS. Existing data/slide descriptions have been included; however, no attempt was made to change the data/descriptions originally prepared by these researchers other than to correct typographical errors. These data appear as they were originally presented unless noted that modifications were made at a later date. Additional Notes The zoom tool allows one to focus on an area of interest. Click on an outcrop (sample) location to open a popup window containing the data for the selected sample(s). The popup window also includes thumbnail photomicrographs of the thin section in both plain polarized light and crossed polarized light. Click the thumbnail to open a full-size image. If interested in specific outcrops or thin sections, use the search tool to query by DGS outcrop ID, lithology, or address. Launch the Delaware Geological Survey Petrographic Data Viewer References Branca, J., 1979, Petrology and structure of the Glenarm Series and associated rocks in the Mill Creek area, Delaware: Newark, Delaware, University of Delaware, unpublished Master's thesis, 84 p. Cohen, A. D., 1964, Petrologic analysis of the gneisses at Windy Hills Bridge, Delaware: Newark, Delaware, University of Delaware, unpublished Geo402 class paper, DGS Sample/thin section record only. Dirska, B., 1990, Petrology and evolution of the plutonic igneous rocks of the Wilmington Complex, northeastern northeastern Delaware and southeastern Pennsylvania: Newark, Delaware, University of Delaware, unpublished Master's thesis, 227 p. Gohn, G.S., John, C.J., Hager, G.M., Niemann, N.L., Grundl, T.J., Bair, P.L., Dempsey, J.M., Ferris, L.A., and Lazzeri, J.J., 1974, Reconnaissance geology of the Mill Creek uplift, northeastern Delaware and southeastern Pennsylvania Piedmont: Newark, Delaware, University of Delaware, unpublished report, 23 p. Hager, G. M., 1976, Petrologic and structural relations of the crystalline rocks in the Hoopes Reservoir area, Delaware: Newark, Delaware, University of Delaware, unpublished Master's thesis, 79 p. Howard, C. S., 1984, Geological and geophysical investigations in the Wilmington Complex/Wissahickon Formation boundary area, Delaware Piedmont: Newark, Delaware, University of Delaware, unpublished Master's thesis, 258 p. Metz, G. W., 1988, The petrology of the cordierite-bearing gneisses near Montchanin, Delaware: Newark, Delaware, University of Delaware, unpublished senior thesis, 44 p. Plank, M. O., 1989,Metamorphism in the Wissahickon Formation of Delaware and adjacent areas of Maryland and Pennsylvania: Newark, Delaware, University of Delaware, unpublished Master's thesis, 111 p. Srogi, L., 1988, The petrogenesis of the igneous and metamorphic rocks in the Wilmington Complex, Pennsylvania-Delaware Piedmont: Philadelphia, Pennsylvania, University of Pennsylvania, unpublished Ph. D. dissertation, 613 p. Ward, R. F., 1958, Petrology and metamorphism of the Wilmington Complex Delaware adjacent Pennsylvania and Maryland: Philadelphia, Pennsylvania, Bryn Mawr College, unpublished Ph. D. dissertation, 103 p. ItemDelaware's Extractive Mineral Industry(Newark, DE: Delaware Geological Survey, University of Delaware, 1981-01) Doyle, R.G.; Pickett, T.E.The purpose of this report is to provide information on the mining industry of Delaware as an essential component of a growing economy. The industry, particularly in sand and gravel mining, must deal with uneven regulation, land use competition, and environmental pressures. It is hoped that the information gathered here will assist planning and regulatory agencies as well as an interested general public in evaluating the role of the extractive mineral industry. ItemDigital Watershed And Bay Boundaries For Rehoboth Bay, Indian River Bay, And Indian River(Newark, DE: Delaware Geological Survey, University of Delaware, 2007) McKenna, T.E.; Andres, A.S.; Lepp, K.P.Digital watershed and bay polygons for use in geographic information systems were created for Rehoboth Bay, Indian River, and Indian River Bay in southeastern Delaware. Polygons were created using a hierarchical classification scheme and a consistent, documented methodology that enables unambiguous calculations of watershed and bay surface areas within a geographic information system. The watershed boundaries were delineated on 1:24,000-scale topographic maps. The resultant polygons represent the entire watersheds for these water bodies, with four hierarchical levels based on surface area. Bay boundaries were delineated by adding attributes to existing polygons representing water and marsh in U.S. Geological Survey Digital Line Graphs of 1:24,000-scale topographic maps and by dissolving the boundaries between polygons with similar attributes. The hierarchy of bays incorporates three different definitions of the coastline: the boundary between open water and land, a simplified version of that boundary, and the upland-lowland boundary. The polygon layers are supplied in a geodatabase format. ItemEffects Of Earthquakes And Earth Tides On Water Levels In Selected Wells In The Piedmont Of Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 1980-02) Talley, J.H.Examination of continuous water-level hydrographs from two artesian observation wells in the Piedmont near Newark, Delaware reveals water-level fluctuations caused by earthquakes and by earth tides. The effects of 14 distant earthquakes with MS (surface wave) magnitudes between 6.7 and 8.0 and MB (body wave) magnitudes between 5.9 and 7.0 (National Earthquake Information Service, 1975-1977) have been recorded over a two-year and ten-month period. ItemEstimate Of Nitrate Flux To Rehoboth And Indian River Bays, Delaware, Through Direct Discharge Of Ground Water(Newark, DE: Delaware Geological Survey, University of Delaware, 1992-05) Andres, A.S.Agricultural fertilizer application, animal (poultry) waste, and wastewater disposal practices of the past 40 years have resulted in widespread nitrate contamination of ground water in coastal Sussex County, Delaware. Discharge of contaminated ground water to Rehoboth and Indian River bays is suspected of being a significant contributor to elevated nutrient concentrations in these surface water bodies, resulting in excessive phytoplankton growth and other related problems. ItemEvaluation Of Remote Sensing And Surface Geophysical Methods For Locating Underground Storage Tanks(Newark, DE: Delaware Geological Survey, University of Delaware, 1986-01) Andres, A.S.Delaware Code, Title 7, Chapter 74, Section 7415 states in part: "The Delaware Geological Survey shall investigate the feasibility of utilizing aerial photographs and other new advanced techniques for locating abandoned tanks." In response to this charge, the Delaware Geological Survey has completed a survey of currently available remote sensing and geophysical tools to determine which methods may be utilized to locate underground storage tanks. Limited preliminary field testing has been performed. ItemGeologic And Hydrologic Aspects Of Landfills(Newark, DE: Delaware Geological Survey, University of Delaware, 1982-03) Spoljaric, N.; Talley, J.H.In the United States more than 3.5 billion tons of solid waste are generated annually. Of this, more than 2 billion tons are agricultural waste, such as manure and crop waste. Almost 300 million tons are generated by commercial and industrial activities and municipalities, and another 1.1 billion tons are attributed to various mining operations (Vaughan, 1969). Increasing amounts of solid waste have had detrimental effects on environmental quality. It has become necessary to reprocess and reuse some, and to provide safe and environmentally acceptable ways of disposing of the remaining waste in properly constructed landfills. Pollution brought about by improperly constructed landfills may be very severe. For example, the contaminants generated by the waste at the old, abandoned Army Creek Landfill, New Castle County, Delaware, were so widespread that the situation received national attention. General and sincere concern expressed by many citizens of our State has prompted the Delaware Geological Survey to prepare this report. The report explains the functioning of a landfill, problems improperly constructed landfills may cause, and the geologic and hydrologic aspects that have to be considered in selecting a suitable disposal site for solid waste. The report does not contain discussions of other important factors, such as social impact, transportation, and specific health hazards, that must also be considered. ItemGeologic And Hydrologic Considerations In The Disposal Of Low-Level Radioactive Wastes(Newark, DE: Delaware Geological Survey, University of Delaware, 1983-06) Spoljaric, NIn view of the possible need for disposal of low-level radioactive waste in Delaware under the Nuclear Waste Policy Act of 1982, the Delaware Geological Survey has prepared this report to assist the citizens of our State in understanding this complex subject. Emphasis here is on geologic and hydrologic aspects of disposal. Health, social, and economic factors are outside the scope of this report and are not discussed. However, they are very important integral parts of the safe disposal of low-level radioactive waste, and must be considered when selecting suitable disposal sites. ItemGeologic Aspects Of Disposal Of Highly Radioactive Nuclear Waste(Newark, DE: Delaware Geological Survey, University of Delaware, 1981-05) Spoljaric, N.This report was prepared to provide a simple but comprehensive overview of programs and concepts of highly radioactive waste disposal. This report is not based on original research, but was prepared from data and information reported in voluminous publications of the U.S. Department of Energy, the Nuclear Regulatory Commission, the U.S. Environmental Protection Agency, and the U.S. Geological Survey. ItemGeologic Cross-Sections, Cenozoic Sediments of the Delmarva Peninsula and Adjacent Area(Newark, DE: Delaware Geological Survey, University of Delaware, 1975) Spoljaric, N. ItemGeologic Field Trips In Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 1977-05) Benson, R.N.; Hahn, W.F.; Jordan, R.R.; Pickett, T.E.; Talley, J.H.; Thompson, A.M.; Woodruff, K.D.The information contained in this Guidebook was compiled on the occasion of the Annual Meeting of the Association of American State Geologists held in Delaware in June 1977. The Delaware Geological Survey is pleased to have been selected to host this national meeting. The field trip logs were designed to familiarize geologists from across the United States with basic features of Delaware's geology and resources. We have also sought to identify some points of historical and cultural interest that may help the visitor become familiar with our State. Experience has shown that field guides retain their usefulness beyond the event that they initially served. They may assist classes, other groups, and individuals seeking additional information about their physical environment. Therefore, this Guidebook has been published as an Open File Report for public distribution. All users of this information are urged to exercise caution, especially at rock faces and along waterways, and to obtain specific permission for visits from landowners where necessary. ItemGeologic Map Of Southern Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 1990-06) Ramsey, K.W.; Schenck, W.S.This geologic map shows: (1) distribution of geologic units found at the land surface; (2) updip limit (generally the northern extent) of Miocene and Pliocene geologic units found in the subsurface; and (3) locations of major subsurface faults that affected deposition of the Miocene and Pliocene geologic units. The geologic units shown are defined on their dominant lithologies (i.e., sand, silt, clay) and other characteristics such as presence or absence of shells or other fossils and range of colors.