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Super-High Resolution Seismic-Reflection-Based Analysis of the Late Pleistocene-Holocene Highstand, Active Newport Channel and its Distributaries, Southern California

A. F. Temeng1, C. K. Paull2, J. A. Covault3, H. Ryan4, R. Sliter4, D. Caress2, and S. A. Graham1
1Stanford University, Stanford, CA, [email protected], [email protected]
2Monterey Bay Aquarium Research Institute, Moss Landing, CA, [email protected], [email protected]
3Chevron ETC, San Ramon, CA, [email protected]
4U.S. Geological Survey, Menlo Park, CA, [email protected], [email protected]

Super-high-resolution multibeam bathymetry (vertical resolution of 0.15-m and horizontal resolution of 1 m at 50 m survey altitude) and chirp seismic-reflection profiles (3.5 kHz; vertical resolution of 0.11 m) were collected by Monterey Bay Aquarium Research Institute’s Autonomous Underwater Vehicle (AUV) in order to examine fine-scale details of the Holocene-active Newport channel and its distributaries offshore southern California. The resolution afforded by these data greatly exceeds industry-standard multichannel seismic-reflection data (typically 10 to 25 m vertical resolution). Recently acquired sparker data (100 to 4000 Hz), older Huntec deep-tow boomer (800 to 1200 Hz), and WesternGeco multichannel seismic-reflection data collected since the 1970s are available to analyze coarser-scale channel geometry and longer-term depositional evolution. As many as 48 radiocarbon ages from 16 piston cores are available in order to establish a chronostratigraphic framework for the latest Pleistocene and Holocene.

Data show up to three coalescing, southwestward-trending, low relief distributary channels at 800 m water depth in the western survey whose features stand in sharp contrast with gentle, nearly flat topography in the eastern survey. The surveys are separated by the left-lateral Carlsbad Ridge fault. Chirp profiles show the cut-and-fill organization of distributary channel-filling turbidites, which have an average thickness of ~2 m. Distributary channels are depressions <1 km wide, with relief <4 m from channel floor to levee top. The aim of this research is to study the stratigraphic architecture of these coalescing distributary channels and characterize their avulsion and depositional history and relationship to the main Newport channel. Additionally, the fine-scale stratigraphic architecture will be correlated with well-documented southern California allogenic influences of sedimentation, including climate, basin tectonics, and sea level. This study provides insight into the finer-scale geometries and internal characteristics of deep-water channel scours and fill and the processes and controls on their formation.

AAPG Search and Discovery Article #90088©2009 Pacific Section Meeting, Ventura, California, May 3-5, 2009