TECTONIC ROTATIONS IN SOUTHERN CALIFORNIA AND THE MOJAVE DESERT DURING NEOGENE TIME
These rotations have occurred during three distinct tectonic regimes. Early Miocene rotations and extension in the central Mojave may have been related to a slab window that formed beneath the region after the Pacific and North American plates came into contact; the Tehachapi and Morro blocks began rotating in this regime also. Capture of the Monterey Plate by the Pacific Plate caused the initiation of rotation under transtension of the western Transverse Ranges, San Gabriel and Catalina blocks at 17 Ma. Shift of the Pacific-North American plate boundary eastward to open the Gulf of California at about 5 Ma created a restraining geometry to the plate boundary. This caused clockwise rotation of the eastern Transverse Ranges and the northeast Mojave Desert and smaller counterclockwise rotation of portions of the western Mojave Desert and the San Gabriel block.