Browsing by Author "Groot, J.J."
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Item Ages Of The Bethany, Beaverdam, And Omar Formations Of Southern Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 1990-02) Groot, J.J.; Ramsey, K.W.; Wehmiller, John F.The microflora of the Bethany formation and the lower part of the Beaverdam Formation is characterized by a Quercus-Carya assemblage, very few non-arboreal pollen, and Pterocarya and Sciadopitys as exotic constituents. This assemblage has much in common with that of the Brandywine Formation of Maryland and the Eastover Formation of Virginia which are of late Miocene or early Pliocene age. The environment of deposition of the Bethany was probably deltaic, and that of the lower Beaverdam fluviatile.Item The Delaware Geological Survey: The Formative Years, 1951-1969(Newark, DE: Delaware Geological Survey, University of Delaware, 1988-06) Groot, J.J.Emphasis is placed herein on the years of Dr. Groot's leadership of the Survey. The remarkable work of James C. Booth in the last century is acknowledged but has elsewhere been entered in history. Some continuing activities of the Survey after 1969 are noted together with comments of an experienced observer; this current period may someday receive the attention of a recorder having the enhanced perspective of time.Item Engineering Materials Of Northern New Castle County(Newark, DE: Delaware Geological Survey, University of Delaware, 1957-11) Ward, R.F.; Groot, J.J.This investigation was undertaken to locate deposits of rock, sand, gravel, fill and borrow in northern New Castle County which may be potential sources of material for highway construction, and to prepare maps and descriptions of the surficial earth materials relative to their geologic and engineering properties.Item Evaluation Of The Water Resources Of Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 1966-03) Baker, W.W.; Varrin, R.D.; Groot, J.J.; Jordan, R.R.At present, Delaware has an abundance of water for the foreseeable future, but is already faced with water problems in some municipalities. These can only be resolved satisfactorily through complete evaluation of the State's water resources and the establishment of a coordinated program of water management.Item Geology and Ground-Water Resources of the Newark Area, Delaware with a section on the Surface Water Resources(Newark, DE: Delaware Geological Survey, University of Delaware, 1954-04) Groot, J.J.; Rasmussen, W.C.; Hulme, A.E.This report describes the geological and lithological conditions in the Newark area, and the occurrence, quantity, and quality of the available ground-water supply. Newark is located on the Fall Line, the boundary between the rolling hills of the Piedmont on the north and the gentle slopes of the Coastal Plain on the south. Because the Piedmont is underlain by dense crystalline rocks and their weathered clayey soils, which are of low water-bearing capacity in contrast to the more permeable silts and sands of the Coastal Plain, the exploration for ground water was confined to the Coastal Plain south and southeast of Newark.Item Geology Of The Milford And Mispillion River Quadrangles(Newark, DE: Delaware Geological Survey, University of Delaware, 1997) Ramsey, K.W.; Groot, J.J.Investigation of the Neogene and Quaternary geology of the Milford and Mispillion River quadrangles has identified six formations: the Calvert, Choptank, and St. Marys formations of the Chesapeake Group, the Columbia Formation, and the Lynch Heights and Scotts Comers formations of the Delaware Bay Group. Stream, swamp, marsh, shoreline, and estuarine and bay deposits of Holocene age are also recognized. The Calvert, Choptank, and St. Marys formations were deposited in inner shelf marine environments during the early to late Miocene. The Columbia Formation is of fluvial origin and was deposited during the middle Pleistocene prior to the erosion and deposition associated with the formation of the Lynch Heights Formation. The Lynch Heights Formation is of fluvial and estuarine origin and is of middle Pleistocene age. The Scotts Corners Formation was deposited in tidal, nearshore, and estuarine environments and is of late Pleistocene age. The Scotts Corners Formation and the Lynch Heights Formation are each interpreted to have been deposited during more than one cycle of sea-level rise and fall. Latest Pleistocene and Holocene deposition has occurred over the last 11,000 years.Item Geology Of The Seaford Area, Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 1996) Andres, A.S.; Ramsey, K.W.; Groot, J.J.This report supplements the map "Geology of the Seaford Area, Delaware" (Andres and Ramsey, 1995). The map portrays surficial and shallow subsurface stratigraphy and geology in and around the Seaford East and Delaware portion of the Seaford West quadrangles. The Quaternary Nanticoke deposits and Pliocene Beaverdam Formation are the primary lithostratigraphic units covering upland surfaces in the map area. Recent swamp, alluvial, and marsh deposits cover most of the floodplains of modern streams and creeks. The Miocene Choptank, St. Marys, and Manokin formations occur in the shallow subsurface within 300 ft of land surface. The Choptank, St. Marys, and Manokin formations were deposited in progressively shallower water marine environments. The Beaverdam Formation records incision of underlying units and progradation of a fluvial-deltaic system into the map area. The geologic history of the Quaternary is marked by weathering and erosion of the surface of the Beaverdam and deposition of the Nanticoke deposits by the ancestral Nanticoke River. Depositional environments in the Nanticoke deposits include fresh water streams and ponds, estuarine streams and lagoons, and subaerial dunes.Item Ground-Water Availability In Southern New Castle County, Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 1983-04) Groot, J.J.; Demicco, P.M.; Cherry, P.J.The purposes of the study described in this report are (1) to determine the total amount of fresh ground water (chloride content less than 150 milligrams/liter) available in New Castle County south of the Chesapeake and Delaware Canal, and (2) to map the geographic distribution of available fresh ground water on the basis of areas delineated by one minute of latitude and one minute of longitude (such areas measure essentially one square mile). The investigation has been based solely on data available in various publications and in the files of the Delaware and United States Geological Surveys.Item High-Capacity Test Well Developed At The Air Force Base, Dover, Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 1958-06) Rasmussen, W.C.; Groot, J.J.; Depman, A.J.A thick aquifer of Eocene age underlies the Dover area, Delaware at depths ranging from 250 to 400 feet below the land surface. The aquifer is about 250 feet thick beneath the Dover Air Force Base and is composed of fairly uniform medium to fine glauconitic quartz sand. The static water level in a test well at the base was 18 feet below the land surface, or 5.7 feet above sea level, on April 17, 1957. The yield of the test well was about 300 gpm (gallons per minute), and the specific capacity at the end of a 12-hour pumping period was 8.3 gpm per foot of drawdown.Item Marine upper cretaceous formations of the Chesapeake and Delaware Canal(Newark, DE: Delaware Geological Survey, University of Delaware, 1954-11) Organist, D.M.; Richards, H.G.; Groot, J.J.In the Coastal Plain of Delaware, the non-marine Cretaceous sands and clays are separated from the Tertiary formations by a series of marine formations of Upper Cretaceous age. The sedimentary and hydrologic characteristics of these formations deserve detailed study because some of them are water-bearing beds. whereas others act as confining beds. A clear understanding of their relative age. and the presence or absence of unconformities is needed for proper correlation with formations found in wells throughout the State. as well as in Maryland and New Jersey.Item Plant Microfossils Of The Calvert Formation Of Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 1992-06) Groot, J.J.The Calvert Formation, deposited in a shallow sea during the late Oligocene and early to middle Miocene (15-27 million years ago), contains a very rich fossil microflora, both in terms of number of specimens and number of species. Most abundant are pollen of oak, pine, and hickory, but exotic taxa (those that no longer occur in Delaware) are present in all samples of this formation. They include pollen of Engelhardia type, Manilkara, Planera (water elm), Alangium(?), and palms. All of these exotics are genera of subtropical or tropical regions, some occurring now in Central America, Florida, and east Asia. The climate during the deposition of the Calvert Formation was probably subtropical and moist.Item The Pliocene And Quaternary Deposits Of Delaware: Palynology, Ages, And Paleoenvironments(Newark, DE: Delaware Geological Survey, University of Delaware, 1999) Groot, J.J.; Jordan, R.R.The surficial Pliocene and Quaternary sedimentary deposits of the Atlantic Coastal Plain of Delaware comprise several formal and informal stratigraphic units. Their ages and the paleoenvironments they represent are interpreted on the basis of palynological and lithologic data and, to a lesser degree, on geomorphology.Item Salinity Distribution And Ground-Water Circulation Beneath The Coastal Plain Of Delaware And The Adjacent Continental Shelf(Newark, DE: Delaware Geological Survey, University of Delaware, 1983-05) Groot, J.J.The possibility of salt-water encroachment into the aquifers of the Coastal Plain of Delaware from saline-water bodies (Chesapeake and Delaware Canal, Delaware Bay, Atlantic Ocean) has received considerable attention (e.g., Sundstrom et al., 1967, 1971, 1976; Woodruff, 1969). These authors have shown that, so far, little encroachment has taken place. It is also known that a large body of highly saline water occurs at depth beneath the Coastal Plain (Upson, 1966; Back, 1966; Brown and Reid, 1976) and the adjacent continental shelf, but no reports have been published about its origin and shape, and the salinity distribution and flow pattern within it. Yet, this saline-water body has a bearing on the development of fresh-water resources throughout Delaware, the feasibility of constructing injection wells for the disposal of liquid wastes, and radioactive waste disposal in the crystalline rocks beneath the Coastal Plain sediments, and upon the occurrence or migration of hydrocarbons (Bredehoeft and Maini, 1981). It is, therefore, important to study this body of saline water.Item Saturated Thickness of the Columbia Formation in Southern New Castle County, Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 1983) Groot, J.J.; Demicco, P.M.; Cherry, P.J.This map shows the saturated thickness of the Columbia Formation. The Columbia Formation covers most of the Coastal Plain of Delaware. Because it consists primarily of coarse sand, it is important to the hydrology of the area. It is an important groundwater reservoir and in most places water must pass through it to reach deeper units. The water budget of the Columbia Formation also influences runoff and baseflow components of streamflow. The saturated thickness was determined through interpretation of data in publications and files of the Delaware Geological Survey, United States Geological Survey, and the Water Resources Center of the University of Delaware. The thicknesses shown on the map represent the best judgment of the authors based on available data. Detailed investigations of specific sites will require additional data.Item Saturated Thickness of the Water-Table Aquifer in Southern New Castle County, Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 1983) Groot, J.J.; Demicco, P.M.; Cherry, P.J.This map shows the saturated thickness of the water-table aquifer. This aquifer consists of the deposits of the Columbia Formation and those portions of the Magothy and Englishtown-Mt. Laurel formations, and Rancocas Group that are hydraulically connected with the Columbia deposits (see Groot, Demicco, and Cherry, 1983). For example, large, saturated thicknesses in the zone trending northeast-southwest near Townsend reflect the addition of the sands of the Rancocas Group to the total thickness of the sands of the overlying Columbia Formation.Item Sedimentary Petrology Of The Cretaceous Sediments Of Northern Delaware In Relation To Paleogeographic Problems(Newark, DE: Delaware Geological Survey, University of Delaware, 1955-07) Groot, J.J.The non-marine Cretaceous sediments of northern Delaware older than the Magothy formation cannot be divided accurately into formations or mappable geologic units because their lithologic characteristics are very similar. However, two heavy mineral zones can be distinguished in these deposits: a lower staurolite-kyanite-tourmaline-zircon zone, and an upper tourmaline-zircon-rutile zone with abundant alterites. They have been named the Patuxent zone and the Patapsco-Raritan zone respectively. The Magothy formation is characterized by abundant staurolite and also contains significant amounts of tourmaline. The marine Upper Cretaceous deposits have a greater variety of heavy minerals than the underlying non-marine sediments. They contain abundant epidote; chloritoid, first appearing at the base of the Merchantville formation, is persistently present. Garnet is found in the Merchantville and the Mount Laurel-Navesink formations. The heavy mineral composition of the Cretaceous sediments is shown in table IV.Item Some Observations On The Sediments Of The Delaware River South Of Wilmington(Newark, DE: Delaware Geological Survey, University of Delaware, 1962-02) Jordan, R.R.; Groot, J.J.A series of cores was obtained from a boring in the sediments of the Delaware River near the Delaware Memorial Bridge. The mineralogy, texture and palynology of these samples have been studied. The sedimentary and palynological records suggest that the Delaware River, while swollen with Wisconsin meltwaters, deepened its channel and that subsequent flooding of the mouth of the stream by rising sea waters initiated the deposition of estuarine silts in post-Wisconsin time.Item The Water Resources Of Northern Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 1957-06) Rasmussen, W.C.; Groot, J.J.; Martin, R.O.R.; McCarren, E.F.; Behn, V.C.Northern Delaware, the area above the Chesapeake and Delaware Canal in New Castle County, is an area of rapidly growing population and expanding industry. In some places the demand for water has reached or exceeded the capacity of the existing facilities creating apparent water shortages. Many agencies, both public and private, are attempting to alleviate these shortages; studies are being made and reports prepared for immediate action as well as long-term planning. It is the purpose of this report to examine on a long-range basis the water resources of the northern Delaware area. This examination indicates that the surface-water and groundwater resources of the area far exceed the 72.8mgd (million gallons per day) used during 1955. The amount of ground water potentially available in the area is estimated to be at least 30 mgd and the amount of surface water potentially available depends principally on the amount of storage that may be feasible economically. Storage of 3 million gallons per square mile would provide an allowable draft rate of 140 mgd with a deficiency at average intervals of ten years, while storage of 30 million gallons per square mile would raise the allowable draft to 250 mgd, which is about half of the mean annual discharge. In addition to the fresh-water resources, saline water from the Delaware River and its tidal estuaries is available in almost unlimited quantity for cooling, fire fighting, some types of washing, and other purposes.Item Wells For The Observation Of Chloride And Water Levels In Aquifers That Cross The Chesapeake And Delaware Canal(Newark, DE: Delaware Geological Survey, University of Delaware, 1958-08) Rasmussen, W.C.; Groot, J.J.; Beamer, N.H.Three test wells were drilled near the banks of the Chesapeake and Delaware Canal, in aquifers formed by sand beds in two geologic units, the nonmarine Cretaceous sediments and the Magothy formation, which crop out along the sides and across the bottom of the canal. The canal carries tidal flow from the Delaware River to and from Chesapeake Bay. The purpose of the wells was to determine whether salt water from the canal has entered the water-bearing beds of these formations, and to determine the head of water in them. It was found that the sands contain fresh water, uncontaminated, and that apparently there was discharge of fresh water from the aquifers to the canal under low head, at least from the winter of late 1955 through early autumn 1957.