Cliffs and wave-cut bench consist of light gray siliceous marine mudstone and sandstone of the Purisima Formation along Drakes Beach, near the Kenneth C. Patrick Visitor Center. The Late Pleistocene wave-cut terraces in the foreground are exposed during the winter months, when increased wave-action exposes them by eroding the beach sand. Purisima Formation (Clark and Brabb, 1997) contain marine fossils that indicate the sedimentary rocks are of Late Miocene age. |