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|Geomorphology and sediments of the Inner New York Bight Continental Shelf
|Williams, S. Jeffress
Duane, David B.
Inner New York Bight
|Coastal Engineering Research Center (U.S.)
Engineer Research and Development Center (U.S.)
|Technical memorandum (Coastal Engineering Research Center (U.S.)) ; no.45.
Abstract: Approximately 445 miles of continuous seismic reflection profiles and 61 vibrating cores were obtained from the Inner New York Bight which encompasses about 250 square miles of the offshore from northern New Jersey and western Long Island. The major physiographic features include Sandy Hook and Rockaway Beach, both prograding barrier islands, Shrewsbury Rocks and the Hudson (submarine) Channel. Shrewsbury Rocks mark the demarcation between two distinct geomorphic provinces. The area north of Shrewsbury Rocks is underlain by Coastal Plain strata which have been deeply eroded by Pleistocene glacial processes and covered by sand and gravel outwash. South of Shrewsbury Rocks Coastal Plain strata have been evenly truncated and covered by a veneer of residual material. Three primary types of bedding have been observed on the seismic records. Coastal Plain strata exhibit a monoclinal regional southeast dip; steeply inclined crossbeds are restricted to an elongate basin east of Sandy Hook, considered to be of fluvial origin. The third type is Pleistocene-Holocene stratified fluvial sands and gravels which are regionally discontinuous, and exhibit gentle seaward dip. Cores reveal that fine to medium sand is the predominant sediment type on the inner shelf. Isolated patches of coarse sand and rounded pea gravels are present off Long Island where fluvial materials are exposed. Coarse sediment off New Jersey is judged to be residual from sea floor outcrops of Coastal Plain strata. Very fine sand, silt and muds comprise the sea floor at the head of the Hudson Channel and along the body. Sand suitable for beach nourishment projects is found in abundance throughout the shallow shelf parts of the Inner New York Bight. Sea floor topography is fairly flat and sand occurs as blanket deposits. It is estimated that over 2 billion cubic yards of clean sand is available for retrieval by present dredging techniques. Comparison of bathymetric maps made from 1845 to 1970 has confirmed that significant parts of the natural Hudson Channel have been filled from ocean disposal of up to 1 billion cubic yards of assorted anthropogenic materials, resulting from early construction in New York City and channel dredging within the estuaries and bays.
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