EVIDENCE FOR THE LATEST PLEISTOCENE-HOLOCENE SHORELINE ALONG THE NEW YORK-NEW JERSEY CONTINENTAL MARGIN

High-resolution subbottom profiling (swept-frequency “Chirp” sonar) and 30 vibracores (2-3 m long) collected during cruise 370 of the R/V Endeavor in May, 2002 allow us to characterize the paleoenvironment, age, and provenance of sediments deposited since the Last Glacial Maximum (21 ka) near the head of Hudson Canyon. We interpret sand-rich mounds up to 10 m high as shoreface, and 10-m-deep troughs containing laminated silty clay as lagoons or tidal inlets. These features overlie a latest Pleistocene offlap surface (informally named pp0) near the present 125 m isobath, and mark the maximum seaward extent of the LGM shoreline. We infer that the head of Hudson Canyon and other shelf-indenting canyons were subaerially exposed to at least that depth below modern sea level. Systems of V- and U-shaped channels, 10 to 20 m deep and 100 to 200 m wide, delivered sediment to the shoreline across the exposed shelf. The wood content of channel fill sediments indicates a terrestrial source. Paleozoic black chert, diabase and garnet found in sands east of the Hudson Canyon are consistent with a Hudson Valley provenance. Constraints on water depth are provided by shallow subtidal (0 – 10 m) shell assemblages (Mesodesma arctatum, Anomia simplex, Ensis directus) and by shell assemblages that reveal subsequent drowning of the shelf (10 – 100 m; Yoldir sapotilla and Clinocardium sp.). Subtidal conditions, manifested by shell and foraminiferal assemblages (Astarte undata, 10 – 90 m water depth; Elphidium sp.), developed also within the fluvial channels during marine transgression. We await radiocarbon chronology from the shells to determine more precise ages for channel formation and transgression.