Browsing by Author "Tomlinson, J.L."
Now showing 1 - 13 of 13
Results Per Page
Sort Options
Item Aquifers and Groundwater Withdrawals, Kent and Sussex Counties, Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 2023-08) McLaughlin, P.M.; Tomlinson, J.L.; Lawson, A.K.Groundwater is the sole source of drinking water and the main source of water for agriculture and industry in central and southern Delaware. This study mapped the depth and thickness of thirteen aquifers in Kent and Sussex Counties, used these maps to assign groundwater withdrawals for 2004 to 2008 to the appropriate aquifer, and analyzed withdrawals for each type of water use by geographic area. The geology of the Delaware Coastal Plain is characterized by a broad complex of surficial Quaternary deposits unconformably underlain by Cretaceous to Cenozoic sediments that dip gently to the southeast. Permeable sands within this succession are used as groundwater sources. The hydrogeologic framework of the study area was characterized by maps of the elevation and thickness of thirteen aquifers. The maps were created in a geographical information system by interpolating aquifer depth data extracted from a database encompassing approximately 6,600 boreholes. The unconfined aquifer occurs in surficial Quaternary and Neogene sands. It is generally less than 100 feet thick in Kent County but varies from a few feet to more than 200 feet thick in Sussex County. The confined aquifers mapped include one Cretaceous (Mount Laurel), two Paleogene (Rancocas and Piney Point), and nine Neogene sand units (lower Calvert, Cheswold, Federalsburg, Frederica, Milford, Middle Choptank, Upper Choptank, Manokin, and Pocomoke). These aquifers are typically tens of feet thick and occur at progressively greater depths southeastward from their recharge areas. The study found that annual groundwater withdrawals for all uses in the study area ranged from approximately 89 to 144 million gallons per day annually for 2004 to 2008. Withdrawals were assigned to aquifers using the aquifer maps and well-screen elevation data. For water-use categories where withdrawals could be attributed to specific wells – public, industrial, and golf courses – aquifers were determined by analyzing well-screen elevations relative to aquifer raster surfaces. For categories in which withdrawals could not be assigned to individual wells – irrigation, domestic self-supplied, and livestock – available well depth data in each category were analyzed by census block and compared to the aquifer raster surfaces; for each block, the proportion of wells in each aquifer was used as the basis for apportioning withdrawals to aquifers. The results indicate that the unconfined aquifer accounted for more than half of groundwater withdrawals. Three shallow, confined aquifers primarily used in Sussex County (confined Columbia, Pocomoke, and Manokin) each provided approximately between 8 and 11 percent of total withdrawals. Withdrawals for the three most important confined aquifers in Kent County (Cheswold, Frederica, and Piney Point) each represented 3 to 5 percent of total withdrawals. Estimated withdrawals were also computed by aquifer for each water-use category and each census block.Item Geologic Map of Offshore Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 2020-02) Mattheus, C.R.; Ramsey, K.W.; Tomlinson, J.L.Delineation of map units is based on sediment-core descriptions (e.g., texture, color, and composition) from 469 locations and seafloor morphology, which was assessed from a seamless NOAA/USGS topo-bathymetric model (Pendleton et al., 2014). The latter was integrated with high-resolution ‘chirper’ seismic reflection data, collected in 2013 by the Delaware Division of Natural Resources and Environmental Conservation (DNREC) and in 2015 as part of the 2015-2017 Bureau of Ocean Energy Management (BOEM) Atlantic Sand Assessment Project (ASAP), using sweep frequency pulses of 2-12 kHz and 0.7-12 kHz, respectively. Stratigraphic mapping based on these data allowed seafloor composition to be inferred across areas of limited core coverage (e.g., Federal waters, beyond 3 miles from shore) and facilitated the delineation of unit boundaries based on subsurface trends and seafloor geomorphology. A minimum surface-unit thickness of 1 ft served as the cut-off for geologic mapping of the seafloor, given the vertical resolution constraints of geophysical data. If surficial sediments were <1 ft thick, the underlying unit was mapped. Unit names and descriptions conform to those established in prior subsurface work along the Delaware barrier shoreline by Ramsey (1999), a synthesis of the Delaware coastal plain geology (Ramsey, 2010), and a previous map which included portions of the offshore surface geology (Ramsey and Tomlinson, 2012).Item Geologic Map of the Bethany Beach and Assawoman Bay Quadrangles, Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 2012-12) Ramsey, K.W.; Tomlinson, J.L.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.Item Geologic Map of the Cecilton and Middletown Quadrangles, Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 2020-09) Tomlinson, J.L.; Ramsey, K.W.Mapping was conducted using field maps at a scale of 1:12,000 with 2-ft contours. Stratigraphic boundaries drawn at topographic breaks reflect detailed mapping using contours not shown on this map. Most stratigraphic units mapped in stream valleys are projected from subsurface data. Except for a few erosional bluffs, these units are covered by colluvium. This map supersedes Geology of the Middletown-Odessa Area, Delaware: Delaware Geological Survey Geologic Map Series No. 2 (Pickett and Spoljaric, 1971). The geology of the map area reflects a complex history with a cut and fill geometry where the Pleistocene-aged deposits incised into older units. The Tertiary deposits were modified by erosion and deposition of the Columbia Formation during the early Pleistocene and again by the Lynch Heights and Scotts Corners Formations as a result of sea-level fluctuations during the middle to late Pleistocene. The geology is further complicated by periglacial activity that produced Carolina Bay deposits in the map area, which modified the land surface.Item Geologic Map of the Elkton, Saint Georges, and Delaware City Quadrangles, Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 2023-05) Tomlinson, J.L.; Ramsey, K.W.Geologic mapping was conducted at 1:12,000 with a 1-ft contour basemap. In some instances, stratigraphic boundaries drawn at topographic breaks reflect detailed mapping using LiDAR data. Elevations of stratigraphic contacts along stream valleys are projected from subsurface data. Except for a few erosional bluffs, these contacts are covered by colluvium. This map supersedes this portion of Geology of the Chesapeake and Delaware Canal Area, Delaware: Delaware Geological Survey Geologic Map Series No. 1 (Pickett, 1970) and Geologic Map of New Castle County, Delaware: Delaware Geological Survey Geologic Map Series No. 13 (Ramsey, 2005). The geological history of the surficial units of the Elkton, Saint Georges, and Delaware City Quadrangles is the result of erosion of the Potomac Formation and younger Cretaceous and Cenozoic units by glacial dam burst events during the early Pleistocene. These periods of erosion were followed by stream incision and fluvial and estuarine deposition associated with multiple sea-level fluctuations during the middle to late Pleistocene. Periglacial activity that followed produced Carolina Bay deposits, alluvium along stream valley slopes, and freeze-thaw features on the land surface.Item Geologic Map of the Frankford and Selbyville Quadrangles, Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 2013-12) Tomlinson, J.L.; Ramsey, K.W.; Andres, A.S.The geological history of the surficial units of the Frankford and Delaware portion of the Selbyville Quadrangles was the result of deposition of the Beaverdam Formation during the late Pliocene and its subsequent modification by erosion and deposition related to sea-level fluctuations during the Pleistocene. The geology at the land surface was then further modified by periglacial activity that produced dune deposits in the map area. Surficial geologic mapping was conducted using field maps at a scale of 1:12,000 with 2 foot contours. Stratigraphic boundaries drawn at topographic breaks reflect detailed mapping using contours not shown on this map.Item Geologic Map of the Harbeson Quadrangle, Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 2011) Ramsey, K.W.; Tomlinson, J.L.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.Item Geologic Map of the Millington, Clayton and Smyrna Quadrangles, Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 2018-04) Ramsey, K.W.; Tomlinson, J.L.The geological history of the surficial units of the Clayton, Smyrna, and the Delaware portion of the Millington Quadrangles are the result of deposition of the Beaverdam Formation and its modification by erosion and deposition of the Columbia Formation during the early Pleistocene. These units were then modified by the Lynch Heights and Scotts Corners Formations as a result of sea-level fluctuations during the middle to late Pleistocene. The geology is further complicated by periglacial activity that produced Carolina Bay deposits in the map area, which modified the land surface. This map supersedes Geologic Map of New Castle County, Delaware (Ramsey, 2005) and Geology of the Geologic Map of Kent County, Delaware (Ramsey, 2007).Item Geologic Map of the Millsboro and Whaleysville Quadrangles, Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 2014-04) Ramsey, K.W.; Tomlinson, J.L.The geological history of the surficial units of the Millsboro Quadrangle and Delaware portion of the Whaleysville Quadrangle was the result of deposition of the Beaverdam Formation during the late Pliocene and its subsequent modification by erosion and deposition related to sea-level fluctuations during the Pleistocene and late Pleistocene upland swamp and bog deposition. The geology at the land surface was then further modified by periglacial activity that produced dune deposits and Carolina Bays in the map area. Surficial geologic mapping was conducted using field maps at a scale of 1:12,000 with 2 foot contours. Stratigraphic boundaries drawn at topographic breaks reflect detailed mapping using contours not shown on this map.Item Geologic Map of the Seaford West and Seaford East Quadrangles, Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 2015-08) Tomlinson, J.L.; Ramsey, K.W.; Andres, A.S.The geological history of the surficial units of the Seaford East Quadrangle and the Delaware portion of the Seaford West Quadrangle was the result 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 by the cut and fill geometry of the middle and late Pleistocene deposits incised into the Beaverdam Formation. The geology is further complicated by periglacial activity that produced dune deposits and the Carolina Bays in the map area, which modified the land surface.Item Geologic Map of the Sharptown, Laurel, Hebron, and Delmar Quadrangles, Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 2014-09) Ramsey, K.W.; Tomlinson, J.L.The geological history of the surficial geologic units in western Sussex County is that of deposition of the Beaverdam Formation and its subsequent modification by erosion and deposition related to the sea-level fluctuations during the Pleistocene. The geology reflects this complex history by the cut and fill geometry of the middle and late Pleistocene deposits into the Beaverdam Formation. The geology is further complicated by periglacial activity that produced dune deposits and Carolina Bays in the map area, which modified the land surface. Mapping was conducted using field maps at a scale of 1:12,000 with 2-ft contours. Stratigraphic boundaries drawn at topographic breaks reflect detailed mapping using contours not shown on this map.Item Geologic Map of the Trap Pond and Pittsville Quadrangles, Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 2014-06) Tomlinson, J.L.; Ramsey, K.W.The geological history of the surficial units of the Trap Pond and the Delaware portion of the Pittsville Quadrangle was the result of deposition of the Beaverdam Formation and its subsequent modification by erosion and deposition related to the sea-level fluctuations during the Pleistocene. The geology reflects this complex history by the cut and fill geometry of the Middle and late Pleistocene deposits into the Beaverdam Formation. The geology is further complicated by periglacial activity that produced dune deposits and Carolina Bays in the map area, which modified the land surface. Surficial geologic mapping was conducted using field maps at a scale of 1:12,000 with 2-foot contours. Stratigraphic boundaries drawn at topographic breaks reflect detailed mapping using contours not shown on this map.Item Stratigraphy And Correlation Of The Oligocene To Pleistocene Section At Bethany Beach, Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 2008) McLaughlin, P.P.; Miller, K.G.; Browning, J.V.; Ramsey, K.W.; Benson, R.N.; Tomlinson, J.L.; Sugarman, P.J.The Bethany Beach borehole (Qj32-27) provides a nearly continuous record of the Oligocene to Pleistocene formations of eastern Sussex County, Delaware. This 1470-ft-deep, continuously cored hole penetrated Oligocene, Miocene, and Pleistocene stratigraphic units that contain important water-bearing intervals. The resulting detailed data on lithology, ages, and environments make this site an important reference section for the subsurface geology of the region.