The San Joaquin Formation

The San Joaquin Formation is an Upper Pliocene-age geologic unit in the San Joaquin Valley that represents the last episode in the valley of marine flooding of the ancient San Joaquin Valley inland sea. Following San Joaquin time the valley became completely filled in by sediments shed from the Sierra Nevada and the Coast Range Mountains, so that the the San Joaquin Formation is overlain by non-marine sediments of the Tulare Formation.