Shore Normal Distribution of Heavy Minerals on Ocean Beaches: Southeast Atlantic Coast

Source: https://erdc-library.erdc.dren.mil/jspui/Cross-shore beach sample sets from 102 locations along the barrier-dominated Atlantic coast from Kitty Hawk, North Carolina, to Palm Beach, Florida, were studied to determine if there were systematic differences in heavy mineral abundance and species frequency distribution between sampling stations on each transect line and between barrier and mainland segments. Only the more commonly occurring heavy minerals species were counted, including rutile, garnet, staurolite, epidote, amphibole, and tourmaline. On each transect, samples were taken at the step, the existing limit of uprush, berm crest, midberm, and inland limit of the beach. The weight percent of the heavy mineral fraction was found to be consistently and substantially higher in backshore and berm crest samples than in the foreshore samples from the same transect. A comparison of the frequency distribution of heavy mineral species showed that mineral species having the higher specific gravity, i. e., rutile, garnet, and staurolite, are much more abundant in backshore samples than in foreshore samples from the same transect and that the amount of difference generally increases with increasing specific gravity. Amphiboles occurred in much greater abundance in foreshore samples, while epidote and tourmaline show less pronounced and consistent differences between backshore and foreshore samples

Review of Geologic Data Sources for Coastal Sediment Budgets

Source: https://erdc-library.erdc.dren.mil/jspui/Sediment budget studies are of great importance in many coastal engineering projects. In general, a sediment budget is a compilation of the sources and amounts of sediment that are gained or lost in designated coastal reaches during a specific interval of time. Sediment supply for a given coastal area may be derived from several sources and may involve different means of transport

Possible Interchange of Sediments between a Beach and Offlying Linear Shoal

Source: https://erdc-library.erdc.dren.mil/jspui/An investigation of Gilbert Shoal, a typical nearshore linear shoal on the Florida Atlantic coast, was undertaken to determine if significant interchange of sediments occur between the shoal, the surrounding seafloor, and the adjacent beach. The principal technique of study made use of selected sediment particle types or particular characteristics such as natural tracers. Sever tracer elements and two particle characteristics were of some use. It was found that some sediment from the shoal reaches the beach, but the amounts involved are small and most of the beach sediment comes from littoral drift, organic shell production on the lower beach and nearshore area, and breakdown of coquina rocks of the Anastasia Formation which crop out on the beach and in the nearshore zone. Gilbert Shoal and the surrounding sea floor apparently recieve little, if any sediment from the beach or nearby St. Lucie Inlet. Gilbert Shoal sediment appears to be derived from the nearby shelf floor and from in situ shell production

Geomorphology and Sediments of Western Massachusetts Bay

Source: https://erdc-library.erdc.dren.mil/jspui/A seismic reflection survey with concurrent bottom sampling was conducted in western Massachusetts Bay to obtain information on bottom topography and sediments, subbottom structure and composition, and the location of sand deposits potentially usable for restoration and nourishment of nearby beaches. Primary data consisted of 242 statute miles of seismic reflection survey and 43 sediment cores. Seismic reflection profiles show that most of the area is underlain by a rock mass with a highly irregular surface below which no coherent reflections appear on available records. Highs in this unit outcrop in places while lows are either partly or completely filled with acoustically transparent material having internal reflection patterns which indicate a stratified deposit. Cores and extrapolation from onshore outcrops indicate that the lower unit consists of dissected basement complex rocks overlain in places by glacial drift and the upper (transparent) unit consists mainly of Pleistocene glaciomarine and Holocene sediments. The predominant sediments of the surface and shallow subsurface (less than 15 feet) deposits in the study area are fine sand, sand and gravel, and clayey silt. Sand suitable for beach restoration and nourishment on the. contiguous coast occurs only locally and in generally small quantity relative to other sediments of the study area. Seven potential borrow sites are located and discussed

Oolites as a Natural Tracer in Beaches of Southeastern Florida

Source: https://erdc-library.erdc.dren.mil/jspui/Calcareous oolites occur in beach and continental shelf sediments from Cape Canaveral, Florida, to as far south as Palm Beach. The abundance of oolites in both shelf and beach sediments is highly irregular. In beach sediments the oolites tend to be significantly more abundant in backshore deposits than in foreshore deposits. This abundance is believed to be due to selective sorting with the oolites responding to flow as heavier particles because of their shape and surface smoothness. The source of the oolites in the beach deposits appears to be the inner continental shelf. Because of their highly irregular distribution and sensitivity to selective sorting processes, it is concluded that quantitative estimates of the total amount of sediment transported ashore with the oolites cannot be made

Geomorphology and Sediments of the Chesapeake Bay Entrance

Source: https://erdc-library.erdc.dren.mil/jspui/The entrance of the Chesapeake Bay and the Atlantic Ocean in the vicinity of Cape Charles and Cape Henry were surveyed to study the bottom morphology and sediments, and subbottom structure, in an effort to locate suitable sand deposits in volumes great enough to economically restore and periodically nourish the shore. Seismic reflection profiles and sediment cores were the basis for the study. Field and laboratory techniques used for the profiles and sediment obtained from the sea floor in lower bay and ocean are presented. Most of the study area is less than 35 feet deep; distribution of shallow bay and inshore terraces and deeper water are shown in the figures. The study included analyses of borings taken along the route of the Chesapeake Bay Bridge Tunnel by the Bridge Commission in 1960 and 1961 .. Cores obtained for a dredging study by the Norfolk District, Corps of Engineers, 1970, were made available and were used in the study

Exploration and Sampling Methods for Borrow Areas

Source: https://erdc-library.erdc.dren.mil/jspui/Beach restoration as a means for mitigating severe storm damage is a major coastal engineering activity in the US Army Corps of Engineers. The single most important element in beach restoration is the availability of sand on a beachfront that is both suitable from an engineering standpoint and stable. Since local financial participation is now legally required on beach restoration projects, improving the efficiency of preconstruction exploration and design techniques has become exceedingly important in overall project management. This study is the first of a series that will examine the state of the art of the various geotechnical and geological technologies used to foster effective and environmentally sound coastal project designs. The current state of knowledge regarding geological indicators of subaqueous, sand-bearing formations is discussed. Existing technology in terms of geophysical equipment and application techniques for exploration programs to locate suitable borrow sources for beach fill are reviewed. Techniques for planning, design, and conduct of field exploration programs are recommended based on experiences covering 30 or more years. The main elements of program planning and design are trackline survey layout, core site selection, scheduling of events, selection of equipment and personnel, and preparation of a realistic cost estimate. Although presently available exploratory equipment is adequate, and there is considerable geological experience in correlating subaqueous geomorphic features to occurrences of sand, there is considerable room for improvement in both areas through future research that could materially lower unit costs for beach sand exploratory programs. Since there is a long-term need for beach restoration, continued improvement in geophysical hardware (in particular, computer enhancement techniques) should be pursued

Reconnaissance Geology of the Inner Continental Shelf, Cape Fear Region, North Carolina

Source: https://erdc-library.erdc.dren.mil/jspui/The Inner Continental Shelf off the North Carolina coast between the South Carolina border and Cape Lookout, North Carolina, was surveyed to obtain information on bottom and subbottom sediment deposits and structures. The location and the extent of deposits of sand suitable for restoration and nourishment of nearby beaches were investigated. Primary kilometers survey coverage consisted of 824 (445 nautical miles) of seismic reflection survey and 139 cores ranging in length from 0.6 to 6.1 meters (2 to 20 feet). More than half of the area surveyed is underlain by two thick sections of Coastal Plain sediments characterized by seaward-dipping progradational internal beds which generate a characteristic acoustic pattern on seismic reflection records. These beds are exposed on the shelf floor in places and elsewhere are covered by a thin sediment blanket. Samples of these extensive units indicate that one is of Cretaceous age and the other of Oligocene age. Both units consist predominantly of fine quartz sand. Other sediment units closely underlying the shelf floor consist of planarto complex-bedded sheet and channel-fill deposits of predominantly quartz sand or biogenic calcium carbonate. These deposits range in age from Eocene to Holocene. Modern sediment accretion on the inner shelf appears to be largely restricted to the shoal fields off Cape Lookout and Cape Fear, and to inlet shoals along the coast. Elsewhere on the inner shelf floor, modern sediments are thin and discontinuous, and modern shelf processes appear to be largely confined to reworking, winnowing, and redepositing older deposits

Sand Resources on the Inner Continental Shelf of the Cape Fear Region, North Carolina

Source: https://erdc-library.erdc.dren.mil/jspui/The inner continental shelf region of North Carolina between the South Carolina border and Cape Lookout was investigated to obtain information on the bottom and subbottom sediment deposits and geologic structure. Primary survey coverage consists of 512 statute miles (824 kilometers) of high-resolution seismic reflection profiles and 124 cores ranging in length from 2 to 20 feet (0.6 to 6.1 meters). Sand suitable for restoration and nourishment of nearby beaches was located, described, and mapped for 27 potential offshore borrow sites. This sand occurs commonly in thin sheet deposits or as relict channel fill. However, extensive sand deposits exist in shoals off Cape Fear and Cape Lookout and in other low, isolated shoals on the shelf floor and within the shoreface area