Abstract

Chirp seismic profiles reveal a prominent seismic facies boundary 0–20 m below the seafloor within an 8.6 × 10.2 km area of the New Jersey outer shelf. This irregular boundary separates seismically transparent facies from underlying stratified facies. The irregularities form two populations of incisions trending northeast and east-northeast. Stratified blocks within the transparent facies, occasionally within presumed incisions, together with lithologic evidence, indicate that some of the transparent facies was formed by disruption of the stratified facies. Preservation of steep (50°–90°) incision flanks implies that deposition of the transparent facies closely followed disruption. Catastrophic erosion and redeposition following the multiple breaching of glacial lake dams to the north ca. 19–12 ka constitute the likeliest mechanisms both for producing facies-boundary incisions and emplacing the transparent facies, implying that local forcing can generate erosional unconformities on periglacial shelves in the absence of base-level change. This facies boundary adds complexity to the already complex, shallowly buried stratigraphic record of the last glacio-eustatic cycle on the New Jersey continental shelf, long considered typical of periglacial shelves worldwide.

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