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Open-File Report 02-221

Field-Trip Guide to the Geology of the Lexington Reservoir and Loma Prieta Areas in the Santa Cruz Mountains, Santa Clara and Santa Cruz Counties, California

By Phil Stoffer and Paula Messina

Thumbnail of and link to report PDF (4.6 MB)Abstract

This guide contains a road log and five stop descriptions for a field trip in the southern Santa Cruz Mountains. The trip officially begins at the boat dock parking area on Alma Bridge Road near the dam of Lexington Reservoir. Stop 1 involves a walk up the Limekiln Trail to examine a large landslide in serpentinite that frequently takes out the trail. Stop 2 is at Miller Point picnic area along the shore of the reservoir where exposures of massive, fractured graywacke sandstone are capped with terrace gravel deposits. Stop 3 is along Highland Way in the Santa Cruz Mountains where large landslides have occasionally force the closure of the road. Stop 4A-C are several closely spaced outcrop areas along Loma Prieta Avenue and Summit-Mt. Madonna Road in the Loma Prieta summit area. A walk to scenic vista points provide opportunity to discuss the evolution of regional landscape along the crest of the Sierra Azul. In addition, a variety of rock types are exposed in the Stop 4 area along a series of road cuts, including Cretaceous age conglomerate, turbidites (consisting of interbedded sandstone and shale), and fossiliferous mudstone. Stop 5 involves returning to the boat dock parking area to examine geology and the placement of the Lexington Dam in the Los Gatos Creek canyon.

First posted September 29, 2002

For additional information, contact:
Geology, Minerals, Energy, and Geophysics Science Center
U.S. Geological Survey
345 Middlefield Road, MS 901
Menlo Park, CA 94025-3591
http://geomaps.wr.usgs.gov/gmeg/

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Suggested citation:

Stoffer, Philip W., Messina, Paula, 2002, Field-Trip Guide to the Geology of the Lexington Reservoir and Loma Prieta Areas in the Santa Cruz Mountains, Santa Clara and Santa Cruz Counties, California: U.S. Geological Survey Open-File Report 02-221, https://pubs.usgs.gov/of/2002/0221/.




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