Origin and evolution of the White Wolf Fault and the Maricopa Basin (MB), southernmost Great Valley (GV), California

Abstract

The White Wolf "fault" (WWF) is a long-lived polyphase structural zone that originated during the Late Cretaceous in continuity with the dextral Kern Canyon fault (KCF). Dextral displacement on the WWF-KCF zone increases southwards from zero at ~36.6°N to ~6 km at 36.2°N, ~12 km at ~35.7°N, and ~40 km adjacent to the MB at ~35.2°N. Southward increase in displacement arises from accumulated SSW directed extension along the zones east wall, which rode on a return flow channel in the shallowly underplated Rand schist subduction complex. Late Cretaceous east wall up displacement also increases from zero southwards to ~10 km at ~35.2°N reflecting greater Late Cretaceous exhumation southwards along the extended wall. The MB is an up to ~10 km deep wedge-shaped basin bounded on the southeast by the WWF, northeast by normal faults of the Kern range front (KRF), and to the west by the Coast Range fold belt. Subcrop mapping of the eastern slopes of the southern GV using basement core and geophysical data indicates that western Foothills belt ophiolitic, metaclastic and cross-cutting Sierran batholithic rocks extend southwards along the eastern half of the GV to the WWF. Southwest of the KRF and across the eastern slope of the MB, basement rocks of the Foothills belt are abruptly transposed into mylonites, chlorite breccias and cataclasites. The basement surface here is a W-dipping detachment fault that was nonconformably overlapped by lower Cenozoic marine strata. Thermochronological data along the KRF and WWF constrain the detachment to have been active in the Late Cretaceous. Southwest displaced upper plate Foothills belt rocks are exposed as an inlier beneath Paleocene marine strata in the western San Emigdio range, having emerged as a result of active north directed folding and thrusting. The WWF-KCF zone was remobilized in the early Neogene as a transfer system that again partitioned NE-SW directed extension, but of lower magnitude, between the MB and the zones east wall. Quaternary north directed thrusts rooted beneath the Tehachapi-San Emigdio Range, which are commonly regarded as the WWF, are ramping northward above the WWF basement structure. The unique configuration of the WWF-KCF zone and the MB arises from their position above a regional lateral ramp in the Rand-Franciscan subduction megathrust system.

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