HR: 1340h
AN: OS53A-0979    [Abstracts]
TI: Latest Pleistocene Deposition and Erosion on the New Jersey Shelf
AU: * Christensen, B A
EM: christensen@adelphi.edu
AF: Adelphi University, 1 South Ave, Garden City, NY 11530, United States
AU: * Christensen, B A
EM: christensen@adelphi.edu
AF: Univ. Texas Institute for Geophysics, 10100 Burnet Road, Mail Code R2200, Austin, TX 78758, United States
AU: Alexander, C
EM: clark.alexander@skio.usg.edu
AF: Skidaway Institute of Oceanography, 10 Ocean Science Circle, Savannah, GA 31411, United States
AU: Stackhouse, S
EM: stanstackhouse@yahoo.com
AF: Univ. Texas Institute for Geophysics, 10100 Burnet Road, Mail Code R2200, Austin, TX 78758, United States
AU: Turner, R
EM: rturner7@student.gsu.edu
AF: Georgia State University, Department of Geosciences, PO Box 4105, Atlanta, GA 30302, United States
AU: Nordfjord, S
EM: sylvianordfjord@gmail.com
AF: Norske Shell, Risavika havnering 300, P.O. Box 40, Tanager, N-4098, Norway
AU: Austin, J
EM: jamie@utig.ig.utexas.edu
AF: Univ. Texas Institute for Geophysics, 10100 Burnet Road, Mail Code R2200, Austin, TX 78758, United States
AU: Goff, J
EM: goff@utig.ig.utexas.edu
AF: Univ. Texas Institute for Geophysics, 10100 Burnet Road, Mail Code R2200, Austin, TX 78758, United States
AU: Gulick, S
EM: sean@utig.ig.utexas.edu
AF: Univ. Texas Institute for Geophysics, 10100 Burnet Road, Mail Code R2200, Austin, TX 78758, United States
AU: Fulthorpe, C
EM: craig@utig.ig.utexas.edu
AF: Univ. Texas Institute for Geophysics, 10100 Burnet Road, Mail Code R2200, Austin, TX 78758, United States
AB: The New Jersey margin is an ideal location for the study of sedimentary response to glacioeustatic forcing because this passive continental edge is both wide and stable. Although the region has been intensively imaged and mapped geophysically, it is still far from being understood stratigraphically because of a lack of samples to constrain timing and paleo-depositional environment. This study examines the timing and nature of latest Pleistocene erosion and deposition on the shelf, using grab samples and core recovered using the AHC-800 (Active Heave Compensation – 800 m) drilling system. The latest Pleistocene shelf is characterized by (1) downcutting and erosion by rivers associated with subaerial exposure during glacial retreat of sea level; (2) deposition at the shelf edge during sea level fall associated with formation of an outer shelf wedge; and (3) deposition in estuarine environments as sea level rose. Foraminiferal and sediment textural analyses of cores samples ground truth previous seismic reflection-based interpretations of incision and paleochannel formation. Grab samples analyzed for foraminiferal content and grain size identify environment of deposition within three main bathymetric features: sand ridges, sand ribbons, and glacial scours. Radiometric dating (14C) further constrains the timing of intervals of erosion and deposition. We relate our results to other studies and suggest a complex, spatially variable shelf response to glacial advance and retreat. K-Ar analyses of hornblende crystals provide constraints on sediment sources. Two assemblages exist: one consistent with ages of Proterozoic age plutons in the New Jersey area, and another, younger, indicating mixing. K-Ar dates show a clear difference between and Holocene (930- 970 +/- 20 Ma) sedimentary assemblages and sediments older than 30 k.y, (850-880 Ma +/- 20-30 Ma). Holocene hornblend crystal ages are consistent with Grenvillian aged plutons common to the source region (e.g., northwestern New Jersey) and were likely delivered to the depositional region by glacial erosion during the last glacial stage. The 40 – 30 Ka aged hornblende crystals are likely a mixture of Grenville and Paleozoic source rocks such as the Cortland complex (55 km north of NYC on the Hudson River), and implies a different source for sediment delivery during stages 4 and 3.
DE: 4219 Continental shelf and slope processes (3002)
DE: 4556 Sea level: variations and mean (1222, 1225, 1641)
DE: 4558 Sediment transport (1862)
DE: 4926 Glacial
DE: 4944 Micropaleontology (0459, 3030)
SC: Ocean Sciences [OS]
MN: 2007 Fall Meeting