Geology of the Soledad Quadrangle, Central California

The area studied is located in the central Coast Ranges of California and about 40 miles inland southeast of Monterey on the Pacific coast. It is nearly 100 miles south of San Francisco. It includes portions of the Santa Lucia and Gabilan Ranges and of the intervening Salinas valley. The pre-Cretaceous basement is divisible into three units, the Santa Lucia granite, the Santa Lucia quartz diorite series, which is the latest intrusive, and the Sur Series (?) of metamorphics. Tertiary and Quaternary formations are found within the Salinas valley and chiefly along the western side. The aggregate thickness of middle Miocene, Pliocene, and Quaternary rocks is approximately 12,000 feet. Pre-Quaternary formations are folded into a composite syncline. Faulting occurred in both the Pliocene and the Pleistocene. In the Pliocene the sediments west of the valley were folded and overthrust. Compressive forces acted from the south and west. The early Pleistocene normal faulting along northwest lines divided the area into two blocks, the Gabilan block southwestward, interrupted the Pleistocene cycle of erosion which had produced the Salinas old age surface, and tilted the King City block towards the west. The displacement of about 4000 feet formed a scarp now somewhat dissected along the western side of the Salinas valley. At the same time movement occurred along several other normal faults within the blocks.