24 Quaternary Geology, Geomorphology, Archaeological Geology
Sunday, 6 May 2007
8:00 AM - 11:30 AM
A REVIEW OF ROCK POLISH WITH AN EXAMPLE OF EXTREMELY HIGH POLISH ON THE ROCKS OF UPLIFTED SEA STACKS ALONG THE NORTHERN COAST OF CALIFORNIA, USA
Paper number: 24-7
Program: Technical Sessions
Time: 10:00 AM – 10:20 AM
Authors
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E. Breck ParkmanCalifornia State Parks, Sonoma, CA
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Timothy McKernanSonoma State University, Rohnert Park, CA
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Rolfe EricksonSonoma State Univ, Rohnert Park, CA
Abstract
Remnant sea stacks on an uplifted Pleistocene wave cut terrace on the coast of Sonoma County north of San Francisco, California, have localized mirror-like polish on their surfaces which extends over areas up to 4 m high. Scanning electron microscope (SEM) and atomic force microscope (AFM) images of this polish, and comparison with wave polish, river polish, slickensides, and various patinas from the cliffs below the terrace and known elephant rubs, indicate that the polished surface was most probably made by large Pleistocene mammals rubbing themselves against the rock. The AFM images demonstrate the extreme planar nature of the mirror surfaces.