Vasquez Formation

The Vasquez Formation, exposed around Vasquez Rocks in southern California, preserves one of the area's oldest non-marine rock records from the Late Oligocene to Early Miocene. Deposited in minibasins between the San Gabriel and San Andreas faults before the San Gabriel Fault became active, it records energetic sedimentation, volcanism, and tectonic change in the early Los Angeles region. Its bright red conglomerates, sandstones, volcanic rocks, and local megabreccia are interpreted mainly as proximal alluvial-fan and occasional rock-avalanche deposits, with a thin lake interval in one part. Unconformities above and below place it between much older basement rocks and younger formations, and its exposures make these processes unusually visible.

California · United States