High-resolution seismic tracing of the transgression across the coastal interface, Brigantine, New Jersey

Abstract

We have repurposed high-resolution marine seismic profiles and vibracores collected from 1 to 10 km offshore Brigantine, New Jersey, to locate, characterize, and interpret the Holocene transgression across the land/sea interface. This storm-dominated, low-slope shelf had experienced large eustatic shifts during the late Pleistocene and Holocene, causing significant lowstand erosion during marine isotope stages (MIS) 6, 4, and 2, leaving fragmented sediment packages from the intervening highstands, which were further eroded by Holocene transgressive wave energy and submarine currents. Using sediment ages tied to seismic reflectors, we mapped the offshore surficial geology of the late Pleistocene and Holocene for the first time in this region. We tied the offshore geology to contiguous onshore surficial geology using borehole geophysical gamma logs, cores, and dated material from barrier-island, estuary, and salt-marsh environments, leading to several new findings, specifically (1) that a back-barrier marsh existed approximately 16 m below the present-day sea level and 7 km seaward of Little Egg Inlet [Formula: see text] (calibrated) before the present (AD 1950), (2) that shoal features were massed in a sediment prism south and west of Little Egg Inlet, and (3) as the Holocene sea level rose, Little Egg Inlet varied little from its current location, fixed in place by the incised valley of the paleo Mullica River, a major upland drainage system since at least MIS 6.