PALINSPASTIC RECONSTRUCTIONS OF SOUTHERN CALIFORNIA AND THE NORTHERN GULF OF CALIFORNIA: IMPLICATIONS FOR MOJAVE AND TRANSVERSE RANGES TECTONIC HISTORIES
Slip discrepancies of ~100 km among various earlier reconstructions of the southern San Andreas are reconciled by along-strike displacement gradients and the conclusion that ~40-60 km of slip occurred on the Mojave segment between ~6.5 and 8-12 Ma. An unacceptible gap opens along the Mojave-Coachella segments of the San Andreas, so one or more of the conditions in (1) or (2) is unrealistic. Comparing the 8-12 Ma reconstruction with those of the Sierra Nevada relative to the Colorado Plateau by Wernicke and Snow (W&S) (1998) show significant mismatch (~100-180 km). Preliminary analysis suggests that the mismatch may be reduced if slip on the Mojave segment began ~8 Ma rather than ~12 Ma, if the western Mojave was not rigid during earlier time slices, and (or) if W&S restore the Sierra Nevada block too far south. Their reconstruction and independent considerations imply Mio-Pliocene clockwise rotation of that block. Coupled with western Mojave deformation, this reduces or eliminates the unacceptable gap, eases space problems at the Garlock-San Andreas junction, and implies that clockwise rotation of the central San Andreas (instead of anticlockwise rotation of the Mojave segment) formed the big bend.