HR: 1330h
AN: OS52B-0917    [PDF]
TI: Acoustic Facies of Late Quaternary Channel and Overbank Systems - Gulf of Santa Catalina, California Borderland.
AU: * Erohina, T
EM: tzvetie@pangea.stanford.edu
AF: Department of Geological and Environmental Sciences, Stanford University, Stanford, CA 94305 United States
AU: Normark, W R
EM: wnormark@usgs.gov
AF: United States Geological Survey, 345 Middlefield Rd, Menlo Park, CA 94025 United States
AU: Sliter, R
EM: rsliter@usgs.gov
AF: United States Geological Survey, 345 Middlefield Rd, Menlo Park, CA 94025 United States
AB: The Gulf of Santa Catalina is a deepwater ($>$300m) basin that lies offshore between Long Beach and Dana Point California. Deep-tow Huntec boomer data from the northern gulf cover a complex channel system consisting of a series of slope gullies euphemistically known as the Newport Canyon. The boomer data have a vertical resolution of 50 cm and the system works effectively for imaging sandy turbidite deposits. A preliminary evaluation of the seismic-reflection data, together with available multibeam bathymetry, provides a better understanding of when different parts of the Newport channel system were active. Three distinct acoustic facies characterize the late Quaternary turbidite sequence of the Newport channel system: an acoustically transparent facies, a high-amplitude discontinuous facies, and a moderate-amplitude sinusoidal facies. The acoustically transparent facies drapes the sea floor on both overbank deposits and some channel floors. Commonly the overbank areas on the west sides of channels preserve the thickest transparent sediment cover. The seismic characteristic of this facies is consistent with a mud-rich deposit but the thickness variation appears to rule out a simple hemipelagic deposit. The high-amplitude discontinuous facies is associated with depressions in the sea floor. These features include active channels, large-scale scours and channel remnants. The moderate-amplitude sinusoidal facies is typical for large amplitude sediment waves. The sediment waves interpreted from the boomer data are not everywhere coincident with the scale of those visible on the multibeam bathymetry. The sediment waves migrate upslope and away from the channel axes. This wave growth pattern is probably related to flows that are substantially thicker than the channel relief and is similar to wave forms found on sediment drifts in the deep ocean. A second channel system similar to the Newport system, associated with the San Gabriel Canyon approximately 9 km to the west, provides additional insight to the depositional processes in the Gulf of Santa Catalina. This system has been strongly affected by the Palos Verdes fault and, therefore, the channel activity is less likely to be autocyclic in nature.
DE: 3022 Marine sediments--processes and transport
DE: 3025 Marine seismics (0935)
DE: 3094 Instruments and techniques
SC: Ocean Sciences [OS]
MN: 2003 Fall Meeting