Moving rocks and clogged plumbing:
fluids, sediment transport and tectonics
of the Monterey Bay Region

H. Gary Greene, Ph.D.
Moss Landing Marine Labs

Wednesday, July 22, 1998
3:30 p.m. — Pacific Forum

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Monterey Bay is located on the Salinian block, a granitic allochthon that is being carried northward by the Pacific Plate. This movement along the North American Plate boundary, the San Andreas fault system, has been active for over 21 million years and during its passage the block has experienced many episodes of emergence/submergence and tectonic deformation. Many of the resultant erosional (Ascension-Monterey canyon system), depositional (Monterey Fan and fluvial-like deposits in submarine canyons) and deformational (canyon meanders and fault zones) products are well defined in the new EM 300 bathymetric data recently collected by MBARI.

The tectonic juggling in and adjacent to Salinia is ongoing and is reflected in the diverse and complex physiography and geomorphology of the region. In the offshore, the new bathymetric data shows fluid-induced mass wasting adjacent to narrow continental shelves associated with areas of rapid uplift (central Santa Cruz and northern Santa Lucia mountain ranges). Many geomorphic features (i.e., rills, pipes, scallops, pockmarks, sheet flows, fluid bulges, slumps) have been identified. These features appear to be concentrated in areas of tranpression.

Sediment transport in the submarine canyons are predominantly of two types: turbidity currents in the lower canyons and sediment cascading in the upper parts. The generally straighter lower canyons are fed sediment from mass wasting resulting from undercutting and fluid- (cognate or salt water?) induced landslides. The fault controlled and meandering upper canyons receive sediments from littoral drift and fluid- (fresh water?) induced mass wasting, which tend to dam sediment by slumps and sediment lobes. Sediment lobes are concentrated in or below oversteepen canyon heads, resulting from rapid tectonic uplift, thereby clogging the narrow, meandering canyons. Time to call Roto-RooterŪ.

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Last updated: December 19, 2000