Physical Sciences and Mathematics Commons^™

Acoustic Geology Of A Portion Of Virginia's Innermost Continental Shelf, Carl H. Hobbs Iii

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Side-scan sonography of the innermost continental shelf between Cape Henry and the Virginia-North Carolina border depicts a relatively typical inner shelf bottom generally characterized by medium density, meso-scale roughness. Subbottom acoustic protiles depict the stratigraphy as a Tertiary age basement separated from Quatenary-age deposits by a regional, angular(?) unconformity. Holocene-age sediments form a discontinuous layer above another unconformity. The area's topography appears to be a function of the presence of the modern sediments.

Heavy Mineral Concentrations In Sediments Of The Virginia Inner Continental Shelf, C. R. Berquist Jr., C. T. Fischler, L. J. Calliari, Et Al

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The Virginia Division of Mineral Resources and the Virginia Institute of Marine Science investigated the occurrence of heavy minerals in the offshore sediments of Virginia. We began the project because earlier reconnaissance studies reported high heavy-mineral concentrations from several samples collected off the Eastern Shore of Virginia. Our work confirms the previously reported mineral values and locates additional high concentrations up to 20 nautical miles offshore. Furthermore, we show that potentially economic mineral values are not restricted no surficial sediments, but also are found in the upper 15 to 20 feet of inner continental shelf sediments. Several core samples indicate …

The Dynamics Of Long-Term Mass Transport In Estuaries, John M. Hamrick

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The dynamics of long-term mass transport in estuaries having weakly nonlinear long wave dynamics are investigated. Low pass filtered long-term mass transport equations are derived for conditions of weak and strong vertical stratification. The dynamics of the residual mass transport velocity, or lowest order approximation to the Lagrangian residual velocity, are investigated by perturbation analyses of the hydrodynamics equations. For weak vertical stratification conditions, analytical results showing the influence of topography, the earth's rotation, and channel curvature on the distribution of the residual mass transport velocity field are presented. The calculation of the residual mass transport velocity field from field …

Heavy Mineral Variability And Provenance Of The Virginia Inner Shelf And Lower Chesapeake Bay, L. J. Calliari, C. T. Fischler, C. R. Berquist Jr.

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The mineral composition of the 3- to 4-phi (0.125 to 0.063 mm) size fraction of 49 surficial grab samples,located north and south of the entrance to Chesapeake Bay and of 38 surficial samples, located in the bay mouth, was determined during this study. Although up to 17 minerals were identified, principal components analysis indicated that seven minerals accounted for 96 percent of the composition variance in the bay samples. By using Q-mode factor analysis, three mineral composition end-members (factors) were selected from the sample data and provided an adequate description of the spatial variation in heavy-mineral composition. The end members …

A Procedure For Assessing Heavy Mineral Resources Potential, Andrew E. Grosz, C. R. Berquist Jr., C. T. Fischler

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Supplies of placer heavy minerals, such as ilmenite, rutile, zircon, and monazite, are anticipated to be in short supply by early in the next century. The depletion of conventional onshore deposits coupled with the declaration of the Exclusive Economic Zone in 1983 have provided the impetus to assess the resource potential of heavy-mineral concentrations in U.S. Continental Shelf sediments as future sources for these mineral commodities.

Mineralogically imprecise assessments of placer resources result from analyses of concentrates derived from small volume samples because of the particle-sparsity effect. The overall low grade of heavy minerals in Atlantic Continental Shelf sediments require …

Quaternary Geology Of The Chesapeake Bay, Jeffrey P. Halka, Steven M. Colman, Carl H. Hobbs Iii

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The Chesapeake Bay, which is a classic coastal plain estuary, is located on a trailing edge continental margin. It has a surface area of nearly 6,000 km2 and ranges in width from 8 to 48 km. The morphology of the bay clearly reflects its formation as a response to fluctuating sea level during and following the last major continental glaciation. The shoreline is highly irregular, the tributaries form an intricate dendritic drainage pattern, and a deep axial channel occurs along much of its length (fig. 1). Water depths commonly exceed 30m in this deep channel, which is flanked by broad …

Monitoring Seagrass Distribution And Abundance Patterns: A Case Study From The Chesapeake Bay, Robert J. Orth, Kenneth A. Moore, Judith F. Nowak

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Seagrasses, or submerged aquatic vegetation (SA V), have been mapped in the Chesapeake Bay five times between 1978 and 1987 with standard aerial photographic techniques, resulting in annual reports on SAV distribution. Acquisition of the vertical photography at a scale of 1:24,000, adhering to strict quality-assurance guidelines based on sun angle, tidal stage, cloud cover, wind speed, and season, has produced excellent, high-contrast imagery delineating beds of SAV from adjacent, unvegetated areas. Ground-truthing data from various State, Federal, and public organizations have corroborated the photographic data base. (more ...)

Persistence Of Residual Currents In The James River Estuary And Its Implication To Mass Transport, Albert Y. Kuo, John M. Hamrick, Gamble M. Sisson

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The distribution and persistence of Eulerian and Lagrangian residual velocity in a cross sectional transect of the James River estuary, Virginia are analyzed. The Eulerian residual velocity has the characteristic two-layered estuarine circulation in the northern half of the transect, however, the net flow is directed downriver at all depths in the shallower southern half of the transect. In the deep channel, the two-layered Eulerian residual circulation is highly persistent over the six month study duration, with disruptions occurring less than 10% of the time when meteorological forcings are intense. No spring-neap tidal cycle variation is apparent. The magnitude of …