American Cordillera
During the Cenozoic,  rock was stuck ("accreted") to the edge of California. Vast areas of marine sedimentary rocks were deposited. Examples of filled basins included the Los Angeles Basin, the Eel River Basin around Eureka and the 50,000 foot thick sedimentary sequences of the Ventura Basin. The San Andreas Fault became most active after the Miocene. It had up to 350 miles of offset in some places.