STRATIGRAPHY AND GENESIS OF A MODERN SHOREFACE-ATTACHED SAND RIDGE, PEAHALA RIDGE, NEW-JERSEY

We investigated the genesis and evolution of Peahala Ridge, a modern s horeface-attached sand ridge 1 km x 6 km in size and 4-7 m in bathymet ric relief, through an integrated sedimentologic and stratigraphic stu dy involving vibracoring, box coring, grab samples, high-resolution se ismic, paleontology, radiocarbon dating, and oceanographic measurement s. Near-surface strata of Peahala Ridge include six important stratigr aphic units: modern shoreface, upper ridge sand, lower ridge sand, swa le/inlet-fill, Middle Holocene back-barrier, and Late Pleistocene stra ndplain. Radiocarbon dating and determination of the stratigraphic rel ationships indicates that Peahala Ridge formed initially from an ebb-t idal delta associated with a tidal inlet. Southwestward migration of t he inlet channel, a vector resultant of landward coastal retreat and s outherly longshore drift, cut and then filled the swale separating Pea hala Ridge from Long Beach Island. Following inlet closure, Peahala Ri dge developed its present form as a shoreface-attached, shoreline-obli que bathymetric feature. Hydrodynamic processes have played a major ro le in evolution of the ridge, including considerable growth and accret ion. This combination of long-term (eustatic) and short term (hydrodyn amic) factors is the best explanation for the present morphology and i nternal stratigraphy of Peahala ridge.