GEOLOGY OF THE NEW JERSEY OFFSHORE IN THE VICINITY OF BARNEGAT INLET AND LONG BEACH ISLAND

New Jersey’s coastal management issues are complex and growing in number. In light of vulnerability to the effects of climate change, human activities, and competition for offshore resources, it is prudent to synthesize offshore geologic data and provide it to the public for informed coastal resources management.

Building on prior analysis of high-resolution (700-2000 Hz) marine seismic and core data from sand-resource assessment, this map correlates offshore data with related stratigraphic analyses of onshore borings and surficial geology. The map area includes parts of Barnegat Bay, Barnegat Inlet (an active, jetty-stabilized waterway), and the storm-dominated, micro-tidal Atlantic nearshore, where 8 to 20 m of Pleistocene and Holocene sediments overlie gently SE-dipping Tertiary Coastal Plain units in the subsurface. Low-relief shore-attached/detached shoals are sculpted by present-day submarine currents.

Cross-sections of onshore well records, lithologic logs, and offshore seismic sections illustrate the following correlations: 1) Marine Isotope Stage (MIS) 5 channel and baymouth sediments with the Cape May Formation, Unit 2 (late Pleistocene); 2) MIS 1 bay/estuarine deposits with Holocene salt-marsh and estuarine deposits; and 3) MIS 1 barrier/shoal sands with Holocene beach and nearshore marine sands. MIS 3 sediments occur offshore only as high as -16 m and do not crop out on land.

Sequence boundary surfaces (MIS 6,4, and 2) and sequence thicknesses (MIS 5,3, and 1) reveal 1) extensive MIS 5 southward-oriented channels; 2) a MIS 3 ENE-WSW-oriented shoreline at 19 meters below sea level; and 3) former inlets at Harvey Cedars and Island Beach. While optical luminescence studies have found MIS 3 sediments as high as +11 m in Virginia, this study does not find MIS 3 sediments in upland terraces. Understanding the stratigraphy strengthens sand prospecting for beach replenishment and dune construction.