HR: 0800h
AN: OS21A-1515    [Abstracts]
TI: Towards a Precise Age Model of IODP Holes U1319B and U1320B (Leg 308, Brazos-Trinity Basin IV, Gulf of Mexico) with Paleo- and Rock Magnetic Methods
AU: * Franke, C
EM: cfranke@uni-bremen.de
AF: Paleomagnetic Laboratory 'Fort Hoofddijk', Utrecht University, Budapestlaan 17, Utrecht, 3584 CD Netherlands
AU: * Franke, C
EM: cfranke@uni-bremen.de
AF: Department of Geosciences, University of Bremen, P.O.Box 330 440, Bremen, 28334 Germany
AU: Heslop, D
EM: dheslop@uni-bremen.de
AF: Department of Geosciences, University of Bremen, P.O.Box 330 440, Bremen, 28334 Germany
AU: Fu, Y
EM: fuyanzhe@hotmail.com
AF: Department of Geosciences, University of Bremen, P.O.Box 330 440, Bremen, 28334 Germany
AU: Flemings, P
EM: flemings@geosc.psu.edu
AF: Department of Geosciences, Penn State University, University Park, PA United States
AU: John, C
EM: cjohn@pmc.ucsc.edu
AF: Department of Earth Sciences, University of California, Santa Cruz, CA United States
AU: Behrmann, J
EM: jan.behrmann@geologie.uni-freiburg.de
AF: Geologisches Institut, Albert-Ludwig-Universitaet, Freiburg, 79098 Germany
AB: During IODP Expedition 308, two sediment sequences (Hole U1319B and Hole U1320B) were recovered from the Brazos-Trinity Basin IV, offshore Texas, Gulf of Mexico. Shipboard measurements of the natural remanent magnetization (NRM) and low-field magnetic susceptibility (k) of the mainly muddy sediments allowed the establishment of a preliminary age model based on cyclostratigraphy. It concurs reasonably well with shipboard micropaleontologic data. The combined age model shows strongly varying sedimentation rates with basal locations in marine isotope stage 6 for both Holes U1319B and U1320B. This age model was refined by further shore-based NRM analysis performed on discrete samples. A higher number of alternating field (AF) demagnetization steps allowed a better definition of the NRM components. A vertical drilling induced overprint was generally removed after the 20 mT AF-demagnetization step. The stable characteristic magnetic component therefore could be determined between fields from 20 to 60 mT. Laboratory induced anhysteretic remanent magnetization (ARM) and isothermal remanent magentization (IRM) provide insights into changes in the magnetic mineral inventory and its grain size distribution. This allows a source area evaluation of the sediment input. ARM, IRM and k provided the opportunity to normalize the NRM and make an estimation of the relative paleointensity, allowing refinement of the preliminary age model.
DE: 1105 Quaternary geochronology
DE: 1520 Magnetostratigraphy
DE: 1521 Paleointensity
DE: 1641 Sea level change (1222, 1225, 4556)
DE: 4219 Continental shelf and slope processes (3002)
SC: Ocean Sciences [OS]
MN: Fall Meeting 2005