HR: 11:20h
AN: OS32A-05    [Abstracts]
TI: Sediment Flux from Source to Sink in the Brazos-Trinity Depositional System
AU: * Pirmez, C
EM: Carlos.Pirmez@shell.com
AF: Shell International Exploration and Production, 3737 Bellaire Blvd., Houston, TX 77025, United States
AU: Prather, B E
EM: Bradford.Prather@shell.com
AF: Shell International Exploration and Production, 3737 Bellaire Blvd., Houston, TX 77025, United States
AU: Droxler, A
EM: andre@rice.edu
AF: Rice University, 6100 Main St., Houston, TX 77005, United States
AU: Ohayer, W
EM: Walter.W.Ohayer@rice.edu
AF: Rice University, 6100 Main St., Houston, TX 77005, United States
AB: During the Late Pleistocene a series of intra-slope basins offshore Texas in the Western Gulf of Mexico, received a high influx of clastic sediments derived primarily from the Brazos, Trinity, and Mississippi rivers. Sediment failures initiated at shelf edge deltas resulted in mass flows that negotiate a complex slope and basin topography caused by salt tectonics. Sediment locally fill ponded basins eventually spilling into subsequent basins downstream. Interaction between these flows and slope topography leads to a complex partitioning of sediment over time and space that can only be unraveled with high-resolution data. The availability of system-wide coverage with conventional 3d seismic surveys, a dense grid of high-resolution 2d seismic lines and cored wells from two of the four linked intraslope basins, makes this locale an ideal area to investigate the transfer of sediment across the continental margin, from river sources to the ultimate sink within an enclosed intraslope basin. Data from IODP Expedition 308 and industry wells, combined with data from previous studies on the shelf constrain an integrated seismic stratigraphic framework for the depositional system. Numerous radiocarbon age dates coupled with multiple stratigraphic tools (seismic-, bio-, and tephra correlations and oxygen isotope measurements) provide an unprecedented high-resolution chronology that allow for detailed estimation of sedimentation rates in this turbidite system and calculation of sediment volumes in each of the basins over time intervals of a few millennia during the late Pleistocene. We find that rates of sedimentation exceed 10 m/kyr during some periods of ultra-fast turbidite accumulation. Rates of channel incision and tectonic subsidence can also be calculated and are comparable to the rapid accumulation rates measured in the basin fill. Our observations indicate that while sealevel changes exert a first order control on delivery of sediment to the basins, the sedimentary record suggests that delta dynamics, basin tectonics and the interaction between gravity flows and basin topography are equally important in determining the distribution of sediments in time and space along this depositional system.
DE: 1105 Quaternary geochronology
DE: 3022 Marine sediments: processes and transport
DE: 8169 Sedimentary basin processes
DE: 9350 North America
SC: Ocean Sciences [OS]
MN: 2007 Fall Meeting