In RR cut on Pleasanton-Sunol Road.
Broad Marine Fauna found, age is Miocene period, Briones formation.
Other Fossil Sites Nearby:
Bolinas Lagoon: link
Mt. Diablo: link
Half Moon Bay: link
One of the most well known and prolific fossil sites in California, Shark Tooth Hill is a reliable source of shark teeth and the fossils of over 175 marine species.
Geology of the Area:
The area was a shallow extension of the Pacific extension during the Miocene epoch, or approximately 12-15 mya, and thus harbored a variety of marine mammals, sharks, birds, rays, skates and even land mammals.
Theories for the strata’s dense fossil record include 1) neighboring volcanic activity poisoned the bay with ash and noxious gases, causing a mass extinction of the organisms, and 2) the bay became landlocked during the Miocene epoch, rendering the inhabitants unable to escape as the waters slowly evaporated in the Pliocene epoch.