HR: 1330h
AN: OS52B-0909    [PDF]
TI: Sedimentology and Age Control of Late Quaternary New Jersey Shelf Deposits
AU: * Alexander, C
EM: clark@skio.peachnet.edu
AF: Skidaway Institute of Oceanography, 10 Ocean Science Circle, Savannah, GA 31411
AU: Sommerfield, C
EM: cs@udel.edu
AF: College of Marine Studies University of Delaware, 700 Pilottown Road, Lewes, DE 19958-1298
AU: Austin, J
EM: jamie@ig.utexas.edu
AF: University of Texas Institute of Geophysics, John A. and Katherine G. Jackson School of Geosciences, 4412 Spicewood Springs Road, Bldg 600, Austin, TX 78759-8500
AU: Christensen, B
EM: bchristensen@gsu.edu
AF: Department of Geology Georgia State University, PO Box 4105, Atlanta, GA 30302-4105
AU: Fulthorpe, C
EM: craig@utig.ig.utexas.edu
AF: University of Texas Institute of Geophysics, John A. and Katherine G. Jackson School of Geosciences, 4412 Spicewood Springs Road, Bldg 600, Austin, TX 78759-8500
AU: Goff, J
EM: goff@ig.utexas.edu
AF: University of Texas Institute of Geophysics, John A. and Katherine G. Jackson School of Geosciences, 4412 Spicewood Springs Road, Bldg 600, Austin, TX 78759-8500
AU: Gulick, S
EM: sean@ig.utexas.edu
AF: University of Texas Institute of Geophysics, John A. and Katherine G. Jackson School of Geosciences, 4412 Spicewood Springs Road, Bldg 600, Austin, TX 78759-8500
AU: Nordfjord, S
EM: sylvia@ig.utexas.edu
AF: University of Texas Institute of Geophysics, John A. and Katherine G. Jackson School of Geosciences, 4412 Spicewood Springs Road, Bldg 600, Austin, TX 78759-8500
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
AU: Nielson, D
EM: dneilson@dosecc.org
AF: DOSECC, 675 South Arapeen Drive, Suite 201, Salt Lake City, UT 84108
AU: Schock, S
EM: sschock@fau.edu
AF: Department of Ocean Engineering Florida Atlantic University, 777 Glades Road, Boca Raton, FL 33431
AB: High-resolution Chirp geophysical profiles have delineated a complex network of shallowly buried stratigraphic features within the New Jersey shelf. These features have been interpreted as fluvial channel incisions ("channels" horizon) and associated infill and regional erosional unconformities (e.g., "R" horizon) related to sea-level fluctuations during the late Quaternary. Age control on these features has been difficult to obtain, hindering geologic interpretations and stratigraphic model development. In addition, the ONR Geoclutter Initiative, also carried out on the New Jersey margin, is seeking to understand and model the interaction of these and similar buried structures with incident acoustic energy from tactical sonars. To address both these needs, drill cores were collected at 3 sites with the DOSECC AHC-800 from the RV KNORR in Sept-Oct 2002. Sites were selected from Chirp profiles to target prominent geologic features and cores were analyzed for texture, AMS C-14 age control and physical properties. These results will be integrated with complementary geophysical studies to provide a better understanding of the Quaternary geologic history of the New Jersey margin. Site 1 (129 m water depth) penetrated the outer shelf wedge, which has been interpreted as predominantly a submarine deltaic deposit. Sediments are sandy from 0-1.0 mbsf, and exhibit ages of ~7-10 kyr BP, whereas deeper than ~1.0 mbsf, sediments are clays interlaminated with silts and are much older, ~32 Kyr BP. This transition from sand to silty clay and a hiatus of 20 kyrs suggests transgression-related nearshore storage of coarser terrigenous material and outer shelf sediment starvation and/or erosion. Site 2 (80 m water depth) penetrated the axis of a large, infilled channel beneath the mid-shelf. These dominantly sandy channel-fill sediments have been previously interpreted as the infill of a fluvial/estuarine(?) system. Below the surficial sand sheet, from ~0.8-3.3 mbsf, ages fall between 12.8 and 12.3 kyr BP, whereas from ~4.0-10.8 mbsf, ages fall between 13.5 and 13.4 kyr BP. The boundary between these two units with distinct age ranges corresponds to a downcore change in dominant sediment type from sand to mud, suggesting a transition from estuarine to nearshore/open marine shelf conditions ~13 kyr BP. Site 3 (76 m water depth) penetrated through both the surficial sand sheet and the "R" erosional unconformity. Although sediments are similarly sandy throughout, ages above "R" are younger than ~10 kyr BP, whereas ages below "R" vary between ~40 and 35 ky BP, confirming previous interpretations of "R" as a lowstand erosional unconformity and/or a transgression-related hiatus.
DE: 4219 Continental shelf processes
SC: Ocean Sciences [OS]
MN: 2003 Fall Meeting