HR: 0800h
AN: OS41D-0524    [Abstracts]
TI: Identification of Late Pleistocene Ice-Rafted Debris (IRD) on the New Jersey Shelf
AU: * Turner, R J
EM: rturner7@gsu.edu
AF: Department of Geology, Georgia State University, 340 Kell Hall, Atlanta, GA 30303 United States
AU: Christensen, B A
EM: bchristensen@gsu.edu
AF: Department of Geology, Georgia State University, 340 Kell Hall, Atlanta, GA 30303 United States
AU: Wampler, J
EM: KayArgon@att.net
AF: Earth and Atmospheric Sciences, Georgia Institute of Technology, 311 Ferst Drive, Atlanta, GA 30332 United States
AU: Uptegrove, J
EM: Jane.Uptegrove@dep.state.nj.us
AF: New Jersey Geological Survey, P.O.Box 427, Trenton, NJ 08625 United States
AU: Goff, J
EM: goff@utig.ig.utexas.edu
AF: University of Texas Institute for Geophysics, 4412 Spicewood Springs Rd. #600, Austin, TX 78759 United States
AB: The purpose of this study is to evaluate the potential for ice-rafted debris (IRD) on the New Jersey shelf and develop procedures for IRD identification on a shelf environment using a variety of techniques to assess texture and age of the sediments. Pleistocene New Jersey shelf sedimentology is strongly defined by glacially driven sea level changes. IRD and its provenance may be identified on a shelf environment through analysis of grain size distribution, heavy mineral content (higher % suggests non-fluvial processes), mineralogical point counts (anomalous mineralogy indicates distal source), isotopic dating methods (age value determination to narrow down potential source rocks), and surface texture analysis (specific glacial transport features). IRD must be differentiated from sediment derived from the NJ bedrock. Likely sources for IRD include the bedrock of Maine and of the southeastern Canadian Shield. Duncan and Goff (2001) reported iceberg grounding along the NJ shelf. IRD is typically identified in the deep sea through anomalously large grain size within pelagic mud, but different methods are needed for the shelf, where regressive shoreline processes, subaerial exposure, fluvial downcutting, and deposition and reworking during transgression have influenced the sediment composition found today. We analyzed grab samples in or near the features believed to be iceberg scour marks and downcore samples from recent Geoclutter drilling in the same area. The coarse grain size fractions of shelf samples were separated by phi classes before heavy mineral separation methods were employed. Initial analyses show high percentages of heavy minerals in the 2 phi and 3 phi size fractions, consistent with past NJ shelf studies. Hornblende grains were hand-picked from select samples for K-Ar dating, providing age values of about 0.96 ñ 0.03 Ga for three sites within iceberg scours. Mineral content of each size fraction is determined by point count. Qualitative assessment of surface textures of select grains as seen with a Hitachi S-2500 SEM is useful in interpretation of source and transport.
DE: 3344 Paleoclimatology
DE: 4219 Continental shelf processes
DE: 4267 Paleoceanography
DE: 3022 Marine sediments--processes and transport
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting