A photo of bedrock.
By Geology and Ecology of National Parks
June 1990 (approx.)
Detailed Description
Older Quaternary alluvial gravels overlie weathered Franciscan bedrock along Highway 1 south of the intersection of Bolinas-Olema Road along Bolinas Lagoon. The age of the gravels is about 55,000 years based on correlation of volcanic ash found in this unit (analysis by Andrei Sarna-Wojcicki, USGS).
Sources/Usage
A photo of bedrock.