Monterey Bay Aquarium Research Institute
Seminars

Reconstructing physical and biological processes in an ancient submarine canyon: The Carmelo Formation at Point Lobos

H. Edward Clifton, Ph.D.
USGS Emeritus

Wednesday, March 17, 2004
Pacific Forum 3:00 p.m.

The Carmelo Formation at Point Lobos consists of conglomerate and sandstone-mudstone of Paleogene age, deposited at bathyal depth in a large, steep-walled submarine valley. The conglomerate is mostly composed of rounded pebbles and cobbles of volcanic rock derived far from the canyon. There are two distinct facies associations present: one conglomeratic and the other composed of sandstone and mudstone. Systematic stratigraphic trends suggest that the facies variation within the canyon was induced by Paleogene sea-level fluctuations.

The distinctive geometries, internal organization, and fabric in the conglomeratic facies indicate depositions from a combination of submarine debris flows, slides, and giant turbidity currents. Very little of the sediment deposited between the flows remains. In contrast, the sandstone-mudstone facies resulted from deposition by small turbidity currents. Due to the limited erosive force, much of the sediment deposited between the flows is preserved. Abundant trace fossils provide a hint of a benthic infaunal community that included decapods, bivalves, and numerous unidentified organisms.

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