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C. W. Poag

Publications and source records attributed to C. W. Poag.

27 records · Page 2Linked to original sources
USGS1989

A record of Appalachian denudation in postrift Mesozoic and Cenozoic sedimentary deposits of the U.S. Middle Atlantic continental margin

The complex interplay between source-terrain uplift, basin subsidence, paleoclimatic shifts, and sea-level change, left an extensive sedimentary record in the contiguous offshore basins of the U.S. middle Atlantic margin (Salisbury Embayment, Baltimore Canyon Trough, and Hatteras Basin). Isopach maps of 23 postrift (Lower Jurassic to Quaternary) a allostratigraphic units, coupled with a revised stratigraphic framework, reveal that tectonism, by regulating sediment supply (accumulation rate), dominated the interplay of forcing mechanisms. Tectonic pulses are evidenced by abruptly accelerated sediment accumulation, marked latitudinal shifts in the location of depocenters, and regional changes in lithofacies. Relatively rapid tectonic subsidence during the Early and Middle Jurassic history of the basins may have enhanced sediment accumulation rates. Beginning in the Late Jurassic, however, subsidence rates decreased significantly, though occasional short pulses of subsidence may have effected relative sea-level rises. Sea-level change heavily influenced the distribution and redistribution of sediments one they reached the basins, and paleoclimate regulated the relative abundance of carbonates and evaporites in the basins. We conclude that source terrains of the central Appalachian Highlands were tectonically uplifted, intensely weathered, and rapidly eroded three times since the Late Triassic: (1) Early to Middle Jurassic (Aalenian to Callovian); (2) mid-Early Cretaceous (Barremian); and (3) Late Cenozoic (Middle Miocene). Intervals of tectonic quiescence following these three tectonic pulses provided conditions suitable for the formation of regional erosion surfaces, geomorphic features commonly reported to characterize the central Appalachian Highlands. This series of three, irregularly spaced, tectonic/quiescent cycles does not, however, match the traditional four-cycle concept of post-Triassic Appalachian “peneplanation”.

Geomorphology↗
USGS1987

Benthic foraminifera of the Panamanian Province: distribution and origins.

Two hundred twenty-nine species of benthic foraminifera have been identified from 96 stations representing 33 localities on the eastern Pacific inner continental shelf, ranging from southern Peru to northern Baja California. Their distributions mark nearshore provincial boundaries that are nearly identical with those previously documented from the distribution of ostracodes and molluscs. Thirteen species are characteristic of the Panamanian Province, one is characteristic of the Chilean-Peruvian Province, and one is characteristic of the newly proposed Sonoran Subprovince. Seventeen species (7%) appear to be endemic to the eastern Pacific. Fifty-eight (25%) of the species recognized are disjunct from population centers in the western Pacific, 134 species (59%) are disjunct from modern assemblages of the Atlanto-Caribbean region, and 40 species (17%) are disjunct from both the western Pacific and the Atlanto-Caribbean. The distribution of the remaining 57 species (25%) is poorly documented; we classify them as of unknown origin.

Journal of Foraminiferal Research↗
USGS1985

Elemental X-ray mapping of agglutinated foraminifer tests: A non- destructive technique for determining compositional characteristics.

The composition of agglutinated foraminiferal tests vary remarkably in response to local substrate characteristics, physiochemical properties of the water column and species- dependant selectivity of test components. We have employed a technique that combines a scanning electron microscope with an energy dispersive X-ray spectrometer system to identify major and minor elemental constituents of agglutinated foraminiferal walls. As a sample is bombarded with a beam of high energy electrons, X-rays are generated that are characteristic of the elements present. As a result, X- ray density maps can be produced for each of several elements present in the tests of agglutinated foraminifers.

Micropaleontology↗
USGS1985

Geologic evolution of the United States Atlantic Margin

This volume compiles the significant findings which began to be accumulated in 1974 during offshore petroleum explorations in the Atlantic Continental Shelf. It's the first presentation of current geological data from the U.S. Atlantic Margin from the inner edge of the coastal plain to the deep sea. A seismic grid of several thousand seismic reflection profiles is correlated with 48 deep borings and the same number of shallow core holes. These profiles are presented on 26 large displays that fold out to as large as 48 x 36''.

Book↗
USGS1984

Distribution and ecology of deep-water benthic foraminifera in the Gulf of Mexico

Bathyal and abyssal foraminifera in the Gulf of Mexico are distributed among thirteen generic predominance facies. Five predominance facies nearly encircle the Gulf basin along the slope and rise; a sixth predominance facies blankets the Sigsbee Plain, and a seventh is restricted to the Mississippi Fan. The remaining eight predominance facies have more restricted distributions. The areal patterns of these predominance facies can be related chiefly to water mass and substrate characteristics; modifications are brought about by calcite dissolution, upwelling, and sill depth. Analysis of ancient generic predominance facies is useful in predicting relative paleobathymetry and other paleoenvironmental properties.

Alabama, Florida, Louisiana, Mississippi, Texas↗
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↗
USGS1978

Stratigraphic test well, Nantucket Island, Massachusetts

The U.S. Geological Survey, in cooperation with the Massachusetts Water Resources Commission and the Nantucket Conservation Foundation, continuously cored 514 m of sediment and volcanic rock in a stratigraphic and water-quality test near the geographic center of Nantucket Island. Stratified sediments were divided texturally into three zones: the upper zone (0-128 m) contains mostly coarse sand and gravel; the middle zone (128-349 m) contains mostly silty clay and a few beds of sand and silt; and the lower zone (349-457 m) contains soft, unconsolidated, clayey sand. Below the lower zone, a saprolite, composed mostly of clay, grades abruptly downward at 470 m into partially altered basalt that extends to the bottom of the hole at 514 m. Calculations based on the Ghyben-Herzberg principle predicted a zone of freshwater 120-150 m thick. This principle is the theory of hydrostatic equilibrium between freshwater and more dense seawater in a coastal aquifer; it states that for each meter of ground-water elevation above sea level, the freshwater lens will depress the saltwater interface about 40 m below sea level. Freshwater or low-salinity brackish water was found in sediments far below the depth predicted by the Ghyben-Herzberg principle. These interstitial waters are probably relict ground water emplaced during times of low sea level during the Pleistocene. (Woodard-USGS)

Circular↗
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↗