Geology
The entire Point Reyes Peninsula is a piece of the Salinian Block transported northward by the San Andreas Fault. Its core is granite, unlike the terrain east of Tomales Bay. The San Andreas Fault runs directly under Tomales Bay.
Point Reyes is bounded to the east by the San Andreas Fault and is structurally dominated by the Point Reyes Syncline. The Point Reyes Peninsula is on the Pacific Plate, while the rest of Marin County land is on the North American Plate. The peninsula is a member of the Salinian Terrane, a segment of the southernmost Sierra Nevada range transported north from Southern California by movement along the San Andreas fault. Simply speaking the peninsula consists of three major members: the Salinian Cretaceous crystalline basement, the overlying Pliocene sedimentary rocks, and the late Pleistocene marine terrace deposits of the southern peninsula.
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