R: 14:05h
AN: OS52F-03 INVITED
TI: Reaping the Benefits of More Than a Decade of "Nesting" on the New Jersey Shelf and Upper Slope
AU: * Austin, J A
EM: jamie@utig.ig.utexas.edu
AF: University of Texas Institute for Geophysics, 4412 Spicewood Springs Rd., Bldg. 600, Austin, TX 78759-8500 United States
AU: Duncan, L
EM: laurie@utig.ig.utexas.edu
AF: University of Texas Institute for Geophysics, 4412 Spicewood Springs Rd., Bldg. 600, Austin, TX 78759-8500 United States
AU: Duncan, L
EM: laurie@utig.ig.utexas.edu
AF: University of Texas at Austin, Department of Geological Sciences, Austin, TX 78712 United States
AU: Fulthorpe, C S
EM: craig@utig.ig.utexas.edu
AF: University of Texas Institute for Geophysics, 4412 Spicewood Springs Rd., Bldg. 600, Austin, TX 78759-8500 United States
AU: Goff, J A
EM: johng@utig.ig.utexas.edu
AF: University of Texas Institute for Geophysics, 4412 Spicewood Springs Rd., Bldg. 600, Austin, TX 78759-8500 United States
AU: Olson, H C
EM: olson@utig.ig.utexas.edu
AF: University of Texas Institute for Geophysics, 4412 Spicewood Springs Rd., Bldg. 600, Austin, TX 78759-8500 United States
AB: A comprehensive geological and geophysical characterization of the uppermost middle-outer New Jersey shelf and uppermost slope is underway, building upon swath backscatter/bathymetric imaging of the seafloor and 2D/3D geophysical control collected over the last decade with ONR support. The goal has been to characterize stratigraphic architecture at various spatial scales and understand its genesis, evolution and preservation using "nested" (multi-frequency) seismic control supported by sampling. UTIG collected ultra-high resolution 3D single-channel Huntec data on the outer shelf starting in 1989; short vibra-cores (up to ~5m long) were collected along with a second 3D survey in 1993. Marion Dufresne-based CALYPSO cores were collected on the outer shelf/upper slope in 1999. Surficial sediment (grab-) sampling, chirp surveys, and sidescan-sonar surveys were also conducted in 1998/9 to assess lithostratigraphic signatures of 95 kHz sidescan coverage collected in 1996. These studies confirm that the surficial, latest Pleistocene-Holocene stratigraphy is: 1) complicated, and 2) not directly related to seafloor morphology. Except for some erosional windows, reworking does not extend to more than ~0.5 m sub-sea floor. Filled, meandering (fluvial? tidal?) channels occur to depths of ~15 m sub-sea floor; sparse ground truth indicates that mid-shelf wedge channels are mud-filled, while outer shelf wedge channels may be sand-filled. A sampled channel-fill exhibits a complex history of shifting base-level changes with a sensitivity of ~10 m, as recorded in the distribution of benthic foram (Elphidium) sub-species. A model now relates observed Huntec stratigraphy and seafloor morphology to depositional/erosional processes associated with the last eustatic cycle, ~120 kyrs BP - Present, but the number and length of subsurface samples collected to date are insufficient to unravel all seismically observed stratigraphic complexities. A grid of high-resolution MCS profiles collected as part of STRATAFORM in 1995 led to ODP Leg 174A drilling on the shelf/upper slope in 1997. Isopach and tructure maps of Miocene sequence boundaries and downlap surfaces (indicators of maximum flooding) beneath the New Jersey shelf/upper slope are relating shelf clinoform geometries and upper slope submarine canyon development to local "regime variables," including sediment transport efficiency, rate of sediment supply, grain size, and spring-sapping(?), in addition to relative sea level changes. True 3D seismic imaging and additional drilling are needed to resolve these complicated relationships properly.
DE: 3000 MARINE GEOLOGY AND GEOPHYSICS
DE: 3025 Marine seismics (0935)
DE: 4219 Continental shelf processes
DE: 0935 Seismic methods (3025)
SC: OS
MN: Fall Meeting 2000