Abstract

We investigated the genesis and evolution of Peahala Ridge, a modern shoreface-attached sand ridge 1 km x 6 km in size and 4-7 m in bathymetric relief, through an integrated sedimentologic and stratigraphic study involving vibracoring, box coring, grab samples, high-resolution seismic, paleontology, radiocarbon dating, and oceanographic measurements. Near-surface strata of Peahala Ridge include six important stratigraphic units: modern shoreface, upper ridge sand, lower ridge sand, swale/inlet-fill, Middle Holocene back-barrier, and Late Pleistocene strandplain. Radiocarbon dating and determination of the stratigraphic relationships indicates that Peahala Ridge formed initially from an ebb-tidal delta associated with a tidal inlet. Southwestward migration of the inlet channel, a vector resultant of landward coastal retreat and southerly longshore drift, cut and then filled the swale separating Peahala Ridge from Long Beach Island. Following inlet closure, Peahala Ridge developed its present form as a shoreface-attached, shoreline-oblique bathymetric feature. Hydrodynamic processes have played a major role in evolution of the ridge, including considerable growth and accretion. This combination of long-term (eustatic) and short term (hydrodynamic) factors is the best explanation for the present morphology and internal stratigraphy of Peahala ridge.

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