May 2020
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22 Reads
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May 2020
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22 Reads
January 2008
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291 Reads
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171 Citations
Journal of Coastal Research
Geologic and geomorphic data on 42 world deltas were compiled for a NASA-sponsored research project. Satellite images from 14 of these deltas (Danube, Ganges, Brahmaputra, Indus, Mahanadi, Mangoky, McKenzie, Mississippi, Niger, Nile, Shatt el Arab, Volga, Huang He [Yellow], Yukon, and Zambezi) were analyzed for delta plain wetland loss caused by natural causes and conversion of wetlands for agricultural and industrial use. These analyses indicated that a total of 15,845 km(2) of wetlands have been irreversibly lost during the past 14 years and the average rate of loss is 95 km(2)/y. If a similar trend is present in the other deltas, a total wetland loss in the delta plains of the 42 deltas would be on the order 364,000 km(2) over the past 15 to 20 years.
November 2007
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44 Reads
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6 Citations
Journal of Coastal Research
Surrounding the Colorado River Delta is the Sonoran sand sea to the east, delta deposits to the north, and basin and range country plus tidal salt flats to the west. Eolian sands at the western end of the sand sea form a 100-m high escarpment between the Sonoran desert-plateau and the Gulf of California. The western edge of the sand sea has a narrow zone of badland topography with well-developed dendritic drainage patterns. Where the sand sea meets the Gulf of Mexico, eolian sands predominate along the strand. Geometry of the spits indicates a net northward transport of eolian sands into the channel and shoal architecture of the delta. An array of longshore mudflats, salt flats, spits, bars, and coastal dunes dominate the shores of the Gulf. The USGS EROS data center provided standard images on CD-ROM to order. Browse images and metadata sets are easily accessible via the Internet. Included are the latest Landsat 7 thematic mapper (ETM+) images exploiting the multispectral. and panchromatic imagery of this new sensor. The image size of Lansat similar to 185 X 185 is particularly valuable in study of deltas because most will fit in a single frame. The revisit time interval of 15 d, however, falls way short of what is needed in coastal waters.
June 2006
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57 Reads
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6 Citations
Sedimentology
Grain-size analyses were performed on 84 samples from six environments in the Burdekin River Delta, NE Queensland, Australia. The data were subjected to a stepwise discriminant function analysis and canonical analysis which showed that the grain-size characteristics of the sediments are sufficiently distinctive to distinguish the six different environments of deposition. The resulting ‘reference set’ was then tested by plotting the grain-size characteristics of 66 samples from different environments of the Mississippi River Delta, Louisiana and Galveston Island, Texas. Seventy-four per cent of the North American samples were correctly classified.
December 2004
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6 Reads
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1 Citation
Marine Technology Society Journal
This article discusses the findings and recommendations of the U.S. Commission on Ocean Policy in the areas of ocean science and education. It argues that an effective national policy should be based on unbiased, credible, and up to date scientific information. Since the oceans remain one of the least explored and most poorly understood environments on the planet, coordinated and enhanced research activities and marine operations are needed to: understand biological, physical, chemical and social processes and interactions; maintain overall ecosystem health and biological diversity; observe, monitor, assess, and predict environmental events and long term trends; explore the ocean depths for new resources; and map ocean and coastal areas for safe navigation and resource management. Using the excitement of ocean science and exploration as a catalyst, all ocean related agencies should explore innovative ways to engage people in learning, thus promoting improved stewardship of the nation's ocean and coastal resources.
December 1996
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35 Reads
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46 Citations
Engineering Geology
Before publication of Fisk's classic scientific papers dealing with the Mississippi River alluvial valley and deltaic plain, geological knowledge of the Holocene deltaic plain was the product of surficial geomorphological studies with a temporal framework provided by archaeology. Fisk and his co-workers provided the third and fourth dimensions, the three-dimensional characteristics of sediment bodies, by numerous deep borings and better chronostratigraphy through14C dating. This research, and the emphasis of his work on fluvial processes, was largely responsible for the form-process approach in sedimentary geology and the awareness that depositional environments are represented by unique sedimentary sequences and properties. Although Fisk made many contributions to deltaic geology, six major areas are noteworthy: delta response to base level changes, sedimentary loading, processes of delta switching, delta abandonment and formation of transgressive sands, river diversion (Atchafalaya distributary), and deltaic sedimentary architecture.
January 1992
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4 Reads
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3 Citations
December 1991
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3 Reads
January 1990
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19 Reads
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33 Citations
Geo-Marine Letters
The continental slope off Texas and Louisiana is the most structurally and sedimentologically complex area in the Gulf of Mexico. This 120,000 km2 area is dominated by diapiric tectonics, resulting in numerous faults, oil and gas seeps, and other geological phenomena that affect near-surface sediments. Bottom gradients range from 0 to 20°. High-resolution seismic surveys, foundation borings, and drop cores reveal several mass-movement features, acoustic wipeout zones, sea floor erosion, faults, hardgrounds, bioherms, reefs, and outcrops. Recent data indicate that most geological activity takes place during relative sea level lowering and low stands.
January 1990
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9 Reads
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7 Citations
Cyclic sequences are extremely common in the geologic record; they are particularly well developed in marine deposits associated with large river systems. Superimposed on cycles attributed to shifting sites of deposition are those related to high-frequency sea-level changes. These latter cycles are well-developed in the near-surface sediments of the Northern Gulf of Mexico shelf. The large data base for this study (471 deep foundation borings, thousands of line kilometers of high-resolution seismic, and sedimentological and dating analyses) represents the most complete information on high-resolution lithostratigraphy that is available on any modern continental shelf/upper slope. These data are used to document sedimentological characteristics and spatial depositional patterns during several complete sea-level cycles over the entire continental shelf/upper slope of offshore Louisiana. Sedimentation during periods of high sea level is characterized by: 1) thin, slowly accumulated depositional sequences, referred to as condensed sections, 2) calcareous-rich deposits, including hemipelagic sediments and shell hashes, and 3) wide lateral continuity. Sedimentation during periods of low sea level is characterized by: 1) variable-thickness, rapidly accumulated sequences referred to as expanded sections, 2) coarse-grained clastic deposits, including abundant sands and gravels, and 3) well-defined depositional trends. Examination of high-resolution seismic records indicates that well-defined, high-amplitude, laterally continuous reflectors correlate with rising and highstand condensed sedimentary sequences and that the deposits laid down during falling and lowstand periods (expanded sections) are characterized by a wide range of acoustic responses. Discontinuous reflectors with high-amplitude variability, continuous parallel reflectors, and chaotic and amorphous zones are common acoustic responses. Even though the data set covers only a short period of geologic time (an estimated 240,000 years), these high frequency events are responsible for the deposition of excellent reservoir-quality facies in well-defined and predictable trends.
... During geological investigations for a proposed nuclear power plant, researchers-using drill cores, geophysical lines, and geologic profilesreported that horizontal Berea layers were pushed down to the southwest and overturned at the creek level by Pleistocene ice movement . Pashin and Ettensohn (1995) explained that the deformed beds at Chappel Creek and Old Woman Creek were due to soft-sediment deformation processes, similar to Holocene mud diapirism, thrust faults, and overturned beds within the Mississippi Delta (Morgan 1961;Morgan et al. 1968). Jones (2000) concurred with the softsediment deformation hypothesis and stated that the sense of rotation on Berea layers at Chappel Creek ruled out glacial deformation. ...
January 1968
... Features like horizontal bioturbation, carbonate clasts, glauconite, fossil content, carbonate cement and erosional contacts implicate the sedimentation in distal delta channels [12] [13]. Some authors [15] [16], mentioned that frequent bioturbation occurs in distal bar environment. The abundance of bioturbation is interpreted as the existence of living biota colonies after the deposition of feeding materials. ...
January 1980
... Prolonged sediment supply, over periods of 10 6 y to 10 7 y, allows the build-up of fan thicknesses from <1 km to over 15 km, and prolongation of the fan radius (or length) from 1 km to 3000 km. Since the 1970s, a number of conceptual models explaining the construction of submarine fan systems have been developed (Normark, 1970;Mutti and Ricci Lucchi, 1972;Walker, 1978;Nilsen, 1980;Stow, 1981Stow, , 1985aMutti and Normark, 1987;Shanmugam et al., 1988;Normark et al., 1993;Reading and Richards, 1994), along with numerous case studies of fans, modern and ancient, throughout the world (Bouma et al., 1985;Shanmugam et al., 1988;Stow, 1992;Pickering et al., 1995;Stow et al., 1996;Stow and Johansson, 2000;Piper and Normark, 2001;Mulder 2011;Pickering and Hiscott, 2015;Hessler and Fildani, 2019). ...
December 1984
... The presence of a fluid-mud bottom, with higher suspended concentrations, changes the form of incoming waves from a sinusoidal to a solitarylike appearance (flatter troughs). Sediment suspension by waves is more likely to occur than by tidal currents in this region due to the solitary-wave characteristics over the fluid mud, where high concentrations are observed (Wells et al., 1978;Wells and Coleman, 1981a). Wave shear stresses generally exceed the stress by tidal currents, and concentrations decay seaward. ...
January 1978
Coastal Engineering Proceedings
... Coastal wetlands offer a variety of ecosystem services, including food production, flood protection, storm surge reduction, water quality improvement, blue carbon sequestration, recreational opportunities, and nursery habitats (Barbier 2013(Barbier , 2016Costanza et al. 2008;Engle 2011;Interis and Petrolia 2016;Mendelssohn et al. 2012;Petrolia et al. 2014). However, wetlands have been lost or degraded dramatically in the last few decades (Blum and Roberts 2012;Davidson and Janssens 2006;Templet and Meyer-Arendt 1988;Walker et al. 1987), especially in the northern Gulf of Mexico (NGOM) (Bourne 2000). The extensive loss in the NGOM has been attributed to sea-level rise, land subsidence, reduced sediment input, storm surge, land conversion, levee constructions, and oil spills, to name a few hypothesized causes (Dahl and Stedman 2006;Reed 1995;Turner and Cahoon 1987;Couvillion et al. 2017;Entwistle, Mora, and Knight 2018;Lin and Shen 2018). ...
April 1987
Geografiska Annaler Series A Physical Geography
... The presence of a fluid-mud bottom, with higher suspended concentrations, changes the form of incoming waves from a sinusoidal to a solitarylike appearance (flatter troughs). Sediment suspension by waves is more likely to occur than by tidal currents in this region due to the solitary-wave characteristics over the fluid mud, where high concentrations are observed (Wells et al., 1978;Wells and Coleman, 1981a). Wave shear stresses generally exceed the stress by tidal currents, and concentrations decay seaward. ...
August 1978
... During the Stage 5 interglacial high-sea-level episode, a significant portion of the Mississippi River drainage was directed toward the western Louisiana shelf. There, a large, sandy highstand delta existed ( Fig. 6; Coleman and Roberts, 1990;Wellner et al., this volume). Likewise, highstand deltas were associated with the ancestral Rio Grande, Colorado, and Brazos Rivers in Texas (Banfield and Anderson, this volume; Abdulah et al., this volume), and with rivers east of the modern Mississippi delta (Fig. 6). ...
January 1990
... We also examined seismic-reflection profiles and SeaMARC sidescan sonar data obtained from R/V Conrad cruise 23-12, archived at Scripps Institution of Oceanography (La Jolla, California, USA), together with reports and peerreviewed publications O'Connell et al., 1985O'Connell et al., , 1991, to assign the deposits to architectural elements of the Mississippi fan. ...
January 1985
... Deep Sea Drilling Project (DSDP) Leg 96 focused primarily on the composition and structure of the Mississippi Fan, where nine cores were taken in the middle and lower fan lobes (Bouma et al., , 1986aStelting et al., 1985). Sediment accumulation rates as high as 10 m/1000 yr were recorded for the middle fan channel during MIS 2-4 (Kohl, 1985). ...
January 1985
... Sediment samples were collected at 5-cm intervals from the surface to greater than 180 cm below the surface (cmbs). Carolina bays are shallow, elliptically shaped wetland depressions (ponds or lakes) oriented (NW-SE in the Carolinas) and occur in large numbers throughout the Coastal Plain portion of the South Atlantic Slope [82][83][84][85][86]. Several hundred thousand bays exist between Maryland and northern Florida, with the greatest concentrations in the Carolinas and Georgia [87]. Carolina bays often exhibit elevated rims represented by fine sand to gravel-sized sediments. ...
January 1987