HR: 1340h
AN: OS33A-0997    [Abstracts]
TI: Growth Patterns of Deep-sea Fans Revisited: Evolving Fan and Related Turbidite-system Morphology in the Inner Basins of the Southern California Continental Borderland
AU: * Covault, J A
EM: jcovault@stanford.edu
AF: Department of Geological and Environmental Sciences, Stanford University, Stanford, CA 94305-2115, United States
AU: Normark, W R
EM: wnormark@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Rd, Menlo Park, CA 94025-3591, United States
AU: Romans, B W
EM: bromans@pangea.stanford.edu
AF: Department of Geological and Environmental Sciences, Stanford University, Stanford, CA 94305-2115, United States
AU: Graham, S A
EM: graham@pangea.stanford.edu
AF: Department of Geological and Environmental Sciences, Stanford University, Stanford, CA 94305-2115, United States
AB: This study quantifies Quaternary fan and related turbidite-system morphologies in the eastern Gulf of Santa Catalina and northern San Diego Trough south from Dana Point to offshore San Diego. Recently, Deptuck et al. (in press) quantified lobe dimensions on fans east of Corsica; our study focuses on entire fans and related turbidite systems, including channel, overbank, and lobe elements. From north to south, the informally-named San Mateo turbidite system together with the Oceanside and Carlsbad fans are recognized on the present seafloor. An extensive grid of industry multichannel and USGS high-resolution deep-tow seismic-reflection data was used to construct a detailed seismic-stratigraphic framework of Quaternary basin fill. The stratigraphic framework shows that the basin fill includes eight phases of growth: three each for the Oceanside and Carlsbad fans and two for the San Mateo turbidite system. Incorporating more than 20 radiocarbon dates younger than 45 ka with the seismic-reflection-based correlations provides a chronostratigraphic framework suitable for extrapolating timing of individual turbidite-system growth phases since Oxygen Isotope Stage (OIS) 6. This study describes turbidite-system morphologies produced by successive growth phases based on ratios of symmetry and thickness to surface area; e.g., Oceanside fan is relatively symmetric and thick following its first growth phase (OIS 6), whereas it is asymmetric and areally extensive following its final growth phase (OIS 2). Underlying basin accommodation and sediment supply to the turbidite systems during growth phases were quantified for comparison with observed system morphologies. Bathymetric gradients and accommodation surface areas prior to growth were used to characterize accommodation, and gross sediment volumes deposited during growth were used to infer sediment supply. Relatively high-relief bathymetric gradients and small accommodation areas facilitate the development of more asymmetric and thick morphologies, whereas relatively large sediment supply can smooth subtle bathymetry and facilitate the development of symmetric morphologies. Placed in temporal context, basin fill became successively thinner and more areally extensive for each phase of turbidite-system growth as a result of depositional smoothing of the original high-relief, tectonically-created basin accommodation.
DE: 3022 Marine sediments: processes and transport
DE: 3045 Seafloor morphology, geology, and geophysics
DE: 8111 Continental tectonics: strike-slip and transform
DE: 8169 Sedimentary basin processes
SC: Ocean Sciences [OS]
MN: 2007 Fall Meeting