SAND RESOURCES OFFSHORE BARNEGAT INLET AND NORTHERN LONG BEACH ISLAND, NEW JERSEY
The analysis integrates a grid of seventy nautical miles of shallow, high-resolution seismic reflection profiles with lithologic data from eight 6-meter vibracores, aged-constrained using amino-acid racemization and radiocarbon dating of shell and plant material. Grain-size samples collected every 30 centimeters down-core (20 samples per core) comprise a direct measurement tool for correlating seismic response to lithologic changes. The U.S. Army Corps of Engineers incorporates these textural data into their model for matching offshore sand with specific beach nourishment sites.
Sediments from the water bottom to a depth of ~30 meters include deposits which date to oxygen isotope stage (OIS) 2/1 (18,000 years ago to the present), OIS 3c (approximately 55 thousand years ago), and OIS 5 (approximately 125 thousand years ago). The OIS 2/1deposits are shore-attached/shore-detached sand ridges composed of coarse to fine sand underlain by 1 to 2 meters of interbedded clay and sand. The OIS 3c deposits are shallow marine or estuarine muds, sands, and gravels. The OIS 5 sands formed as extensive bay-mouth shoal complexes and estuary channel structures.
The identified sand resource in Area C is a shoal feature with a maximum thickness of 7.5 meters of OIS 2/1 sediments as described above, including suitable sand as thick as 6+ meters. Resource volume is constrained by defining the shoal perimeter as the 3-meter isopach contour and setting a 1.5-meter buffer at the base of the Holocene sequence to exclude the sand/clay interbeds.
By contrast, remnant OIS 3c shallow marine or estuarine interbedded clays, sands, and gravels comprise the elongate bathymetric high in Area D. This mixed lithology is unsuitable as beach nourishment material.