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F. A. Kohout

Publications and source records attributed to F. A. Kohout.

12 recordsLinked to original sources
USGS2007

Reply to discussion by Michael A. Collins, "Fresh ground water stored in aquifers under the continental shelf: implications from a deep test, Nantucket Island, Massachusetts"

We appreciate the comments made in the discussion by Michael A. Collins , regarding o ur paper about the anomalously low salinity of water underlying Nantucket Island. However, we feel that in his effort to justify the mathematical approach for solving salt water intrusion problems, he has overlooked several of the major points in this paper. We will try to amplify these points to establish that, indeed, the situation at Nantucket is anomalous, contrary to Collins’ negative conclusion (Collins, 1978).

Massachusetts↗
USGS2006

Some aspects of sampling salty ground water in coastal aquifers

Investigations of the fluctuations of chloride content in wells that tap the zone of diffusion between fresh and salt water show that the salty well water behaves erratically when the well is pumped. Frequently, a static distribution of chloride content that ranges from less than 1,000 ppm at the top to more than 10,000 ppm at the bottom is present in the open‐hole part of a well. When the well is pumped, the discharge water tends to come from the upper part of the open hole because less energy is expended by removal of low‐density water from this region than by removal of high‐density water from the lower part of the open hole. Where the permeability of strata in the deep part of the open hole is greater than that in the shallow part, the tendency for natural selection of the less dense, shallow water is suppressed, and practically all the water in the blend comes from the deep part. As a result of this complex interrelation of hydraulics, distribution and density of the salt water , and permeability, the depth at which the pumped water enters the well bore is indeterminate. This deficiency leads to the use of multiple‐depth‐bottle, windshield‐wiper, and electrical‐conductivity sampling techniques for collection of data used in constructing maps and cross sections that show the areal‐depth relations of salt water in the Biscayne aquifer of the Miami area, Florida.

Groundwater↗
USGS1984

Seismic reflection studies of sinkholes and limestone dissolution features on the northeastern Florida shelf

High-resolution seismic-reflection profiles show that the shelf off northern Florida is underlain by solution deformed limestone of Oligocene, Eocene, Paleocene and late Cretaceous age. Dissolution and collapse features are widely scattered. They are expressed in three general forms: as sinkholes that presently breach the sea floor, such as Red Snapper Sink and the Crescent Beach submarine spring; as sinkholes that have breached the seafloor in the past but are now filled with shelf sands; and as dissolution collapse structures that originate deep within the section and have caused buckling and folding of overlying Eocene, Oligocene, and to a lesser extent, Neogene strata. Although deformation caused by solution and collapse can be shown to be a continuous process, the major episode of karstification occurred in the late Oligocene and early Miocene when the shelf was exposed to subaerial conditions.

Conference Paper↗
USGS1979

U.S. Geological Survey core drilling on the Atlantic shelf

The first broad program of scientific shallow drilling on the U.S. Atlantic continental shelf has delineated rocks of Pleistocene to Late Cretaceous age, including phosphoritic Miocene strata, widespread Eocene carbonate deposits that serve as reflective seismic markers, and several regional unconformities. Two sites, off Maryland and New Jersey, showed light hydrocarbon gases having affinity to mature petroleum. Pore fluid studies showed that relatively fresh to brackish water occurs beneath much of the Atlantic continental shelf, whereas increases in salinity off Georgia and beneath the Florida-Hatteras slope suggest buried evaporitic strata. The sediment cores showed engineering properties that range from good foundation strength to a potential for severe loss of strength through interaction between sediments and man-made structures.

Science↗
USGS1976

Preliminary summary of the 1976 Atlantic Margin Coring Project of the U.S. Geological Survey

The U.S. Geological Survey Atlantic Margin Coring Project, 1976, a 60-day expedition to obtain core samples by drilling beneath the floor of the Continental Shelf and Slope of the eastern United States, was carried out in July, August, and September 1976 aboard D/V GLOMAR CONCEPTION. The coring penetrated as much as 310 meters below the sea floor at 19 sites along the continental margin from Georgia to Georges Bank off New England in water depths ranging from 20 to 300 meters; 1,020 meters of material were recovered in 380 cores, ranging in age from Late Cretaceous to Holocene. One of the major findings was the discovery of relatively fresh water (salinities less than 3 parts per thousand) extending beneath the Continental Shelf as much as 60 nautical miles seaward from the New Jersey coast. Water of about 1 part per thousand salinity was found beneath the shelf more than 7 nautical miles off Ocean City, Maryland and Barnegat Inlet, New Jersey. Analyses for light hydrocarbons in the cores show the highest concentrations (as much as 412,000 ppm) at sites in water depth greater than 200 meters (the shelf-slope break), principally in Pleistocene sediments, although methane concentrations greater than 400,000 ppm also were found in Miocene sediments at one site near the shelf edge. (Woodard-USGS)

Open-File Report↗
USGS1976

Fresh ground water found deep beneath Nantucket Island, Masachusetts

In a deep water-resources and stratigraphic test well near the center of Nantucket Island, about 30 miles (48 kilometres) off the New England coast, freshwater has been found at greater depths than predicted by the Ghyben-Herzberg principle. An uppermost lens of freshwater, which occupies relatively permeable glacial-outwash sand and gravel to a depth of 520 feet (158 metres), is believed to be in hydrodynamic equilibrium with the present level of the sea and the height of the water table. However, two zones of freshwater at 730 to 820 ft (222-249 m) and 900 to 930 ft (274-283 m) are anomalously deep. Although several explanations are possible, the most likely is that the entire surface of the Continental Shelf was exposed to recharge by precipitation during long periods of low sea level in Pleistocene time. After the last retreat of glacial ice, seawater rapidly drowned the shelf around Nantucket Island. Since then, about 8,000 years ago, the deep freshwater zones which underlie dense clay layers have not had time to adjust to a new equilibrium. Under similar circumstances, freshwater may remain trapped under extensive areas of the Continental Shelf wherever clay confining beds have not permitted saltwater to intrude rapidly to new hydrodynamic equilibria positions. The implications are far reaching because all continental shelves worldwide were exposed to similar hydrologic influences during Pleistocene time.

Massachusetts↗
USGS1967

Hydrologic effects of area B flood control plan on urbanization of Dade County, Florida

Swampy low land (Area B) that fringes the Everglades west of Metropolitan Miami, Florida (Area A) probably will be urbanized in the future. Area B will be protected from flooding by huge pumps that will pump water westward from Area B over a levee system into Conservation Area 3B. The total capacity of the pumps will be about 13,400 cubic feet per second which is sufficient to lower water levels 2 inches per day in the 203 square miles of Area B. As this capacity is about equal to the highest gravity-flow discharge to the ocean through existing canals of the Miami area, a great potential. will exist, not only for control of floods, but also for beneficial control and management of a major segment of the water resources in southeastern Florida.

Florida↗