HR: 1330h
AN: OS52B-0905    [PDF]
TI: Mapping a Pre-Last Glacial Maximum Paleo-Seafloor and Shelf-Slope Sediment Wedges beneath the New Jersey shelf
AU: * Gulick, S P
EM: sean@ig.utexas.edu
AF: University of Texas Institute for Geophysics, John A. and Katherine G. Jackson School of Geosciences, 4412 Spicewood Springs Road, Bldg. 600, Austin, TX 78759-8500 United States
AU: Fulthorpe, C S
EM: craig@ig.utexas.edu
AF: University of Texas Institute for Geophysics, John A. and Katherine G. Jackson School of Geosciences, 4412 Spicewood Springs Road, Bldg. 600, Austin, TX 78759-8500 United States
AU: Goff, J A
EM: goff@ig.utexas.edu
AF: University of Texas Institute for Geophysics, John A. and Katherine G. Jackson School of Geosciences, 4412 Spicewood Springs Road, Bldg. 600, Austin, TX 78759-8500 United States
AU: Austin, J A
EM: jamie@ig.utexas.edu
AF: University of Texas Institute for Geophysics, John A. and Katherine G. Jackson School of Geosciences, 4412 Spicewood Springs Road, Bldg. 600, Austin, TX 78759-8500 United States
AU: Nordfjord, S
EM: sylvia@ig.utexas.edu
AF: University of Texas Institute for Geophysics, John A. and Katherine G. Jackson School of Geosciences, 4412 Spicewood Springs Road, Bldg. 600, Austin, TX 78759-8500 United States
AU: Nordfjord, S
EM: sylvia@ig.utexas.edu
AF: University of Texas at Austin, Department of Geological Sciences, John A. and Katherine G. Jackson School of Geosciences, 1 University Station C1100, Austin, TX 78712 United States
AU: Sommerfield, C
EM: cs@udel.edu
AF: College of Marine Studies, University of Delaware, 700 Pilottown Road, Lewes, DE 19958-1298 United States
AU: Alexander, C
EM: clark@skio.peachnet.edu
AF: Skidaway Institute of Oceanography, 10 Ocean Science Circle, Savannah, GA 31411 United States
AU: Christensen, B
EM: bchristensen@gsu.edu
AF: Department of Geology, Georgia State University, 340 Kell Hall, Atlanta, GA 30303 United States
AU: Schock, S
EM: sschock@fau.edu
AF: Department of Ocean Engineering, Florida Atlantic University, 777 Glades Road, Boca Raton, FL 33431 United States
AU: Nielson, D L
EM: dnielson@dosecc.org
AF: DOSECC, Inc., 675 South Arapeen Drive, Suite 201, Salt Lake City, UT 84108 United States
AB: The New Jersey margin has been intensively investigated but attempts to gather geophysical ground truth through coring have seen limited success. In 2001 and 2002, cruises funded by ONR have resulted in a suite of ultra-high resolution chirp reflection lines and shallow drilling using the DOSECC AHC 800 system, placed on board the R/V Knorr. The purpose of these experiments is to determine the geologic history of the margin during the last eustatic sea-level cycle. A key marker for examining the late Pleistocene-Holocene history is a high-amplitude seismic reflector which has been called "R". Previous coring has shown "R" to lie atop sediments ~47 ka; however, the surface is likely time-transgressive. "R" underlies the so-called mid-shelf corridor of the New Jersey margin from Cape May to the Hudson Paleo-Shelf Valley, and changes west to east from a sub-horizontal reflector lying on average $<$9 m beneath the modern seafloor to an eastward dipping reflector that forms the base of two sediment wedges. This transition occurs across three discrete changes in the dip (inflections) of the "R" reflector that can be traced for 10s of km along a trend of N35degE, differing from the modern isobaths in strike by ~15 degrees. The first change in dip occurs across an erosional zone previously described as the "R" outcrop area. Sediments overlying "R" between the first and second inflection points thicken by a factor of two and in places display stratified lower layers. The second inflection in "R" marks the westernmost limit of the outer shelf wedge, which is characterized by a stratified lower unit that thins seaward, overlain by a non-reflective unit, which is in turn overlain by a series of eastward-dipping stratified units. AHC 800 drilling penetrated through one of these shallow stratified units, confirming that the contact of stratified to non-reflective sediments is a change from interbedded sands and clays downward to denser, massive clay. We infer the lower stratified unit of the outer shelf wedge to be a return to interbedded sands and clays. The third inflection (~12 km east) is the western limit of a previously unmapped sediment wedge that post-dates the outer shelf wedge and consists of stratified reflectors. Based on the geometry of "R" and the pair of wedges deposited east of the inflections in "R", we interpret the reflector to be paleo-seafloor and the inflections to mark a succession of eastward-migrating shelf-edges during sea level fall. Existing ages and the stratified reflections within the wedges argue against rapid emplacement, but rather a process that involves continual shedding of sediments off the evolving paleo-shelf edge by reworking, preceding and possibly following the last glacial maximum.
UR: http://www.ig.utexas.edu/research/projects/geoclutter/geoclutter.htm
DE: 3022 Marine sediments--processes and transport
DE: 3025 Marine seismics (0935)
DE: 4219 Continental shelf processes
DE: 4556 Sea level variations
SC: Ocean Sciences [OS]
MN: 2003 Fall Meeting