text
The map show above shows the areal extent of the various exposed rock units (Cretaceous age granitic rocks and Tertiary age sedimentary formations) and surficial deposits (soil, dunes, etc.) exposed on the Point Reyes peninsula. Point Reyes is bounded on the east by the flooded rift valley of the San Andreas Fault (Tomales Bay), and to the west by the Pacific Ocean. The granitic basement rocks were derived from source areas probably in the southern California region; great "blocks" of these ancient crustal rocks gradually rafted northward by strike-slipe fault motion over many millions of years along the San Andreas Fault system. The west side of the fault is moving to the northwest relative to the east side.
For a detailed description of the geology of Point Reyes National Seashore see: Clark, J.C. and Brabb, E.E., 1997., Geology of Point Reyes National Seashore and Vicinity, California; A Digital Database: U.S. Geological Survey, Open-File Report 97-456
 |