The Monterey Fan Channel Turbidite Record Offshore Central California: Insights into Submarine Canyon Processes

J. E. Johnson¹, C. K. Paull², W. R. Normark³, and W. Ussler^2
1University of New Hampshire, Durham, NH, [email protected]
²Monterey Bay Aquarium Research Institute, Moss Landing, CA, [email protected], [email protected]
³U.S. Geological Survey, Menlo Park, CA

The Monterey Canyon and Fan Channel System is one of the major and active conduits for sediment transport on the California margin. The proximity of the canyon head to the shoreline, coupled with longshore sand transport in Monterey Bay, allows frequent (several/year) sediment gravity flows to enter the canyon and deposit coarse gravel and sand down the canyon axis (Paull et al, 2005). Recent canyon monitoring activities and an opportunistic whale carcass, however, suggest these events do not deposit materials beyond the canyon in the active fan channel. In 2005, to address how frequently turbidity currents pass through the fan channel, we used an ROV-mounted vibracore to collect closely spaced cores in transects across the active fan channel. Observations from the most complete transect of cores at a prominent bend in the fan channel document unprecedented channel facies variability and show that a narrow region along the inner bend levee preserves the most complete event record (11 correlated events). Radiocarbon data for the youngest 4 events suggest an average event recurrence of ~220 years, much longer than the upper canyon recurrence of sediment gravity flows and remarkably similar to the Holocene recurrence of potentially earthquake triggered turbidites documented in canyons to the north (Goldfinger et al., 2007). The Monterey data suggest a dual frequency behavior for the canyon-fan channel system during the latest Holocene, where upper canyon events, although frequently deposited, are limited in extent to the canyon, and full canyon to fan channel flushing events, which may recycle and redeposit the upper canyon materials, occur at a longer timescale. This Holocene (highstand) dual frequency behavior may exist in other submarine canyon systems as well, especially along non-sediment starved margins with canyon heads close to the shore.

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