Late Cenozoic history and styles of deformation along the southern Death Valley fault zone, California

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Late Cenozoic deposits in the southern Death Valley region have been offset ∼35 km by right-lateral, strike-slip faulting on the southern Death Valley fault zone since Miocene time. Virtually all slip took place prior to ∼1 m.y. ago along western traces of the fault zone. During the past 1 m.y., the eastern traces of the fault zone have been active and characterized by oblique slip, with a lateral component of only a few hundred metres. Movement along these eastern traces has formed normal faults and gentle-to-isoclinal folds that have uplifted fan gravel and lacustrine sediments as much as 200 m above the modern alluvial fan surface. Surveying of the longitudinal profile of the Amargosa River, which flows within the eastern traces of the fault zone, suggests that vertical deformation continues today. The 35 km of right-lateral offset, which is based on matching offset alluvial fan gravel with its source area, refines earlier estimates of 8 to 80 km of movement for the southern Death Valley fault zone, and it is consistent with the geometry of a pull-apart basin model for central Death Valley. Causes for the observed differences in the style and timing of movement of the eastern and western subzones are not well understood. The study area, however, is located a few kilometres north of the intersection of the southern Death Valley and Garlock fault zones. The Garlock fault zone changes its sense of movement from left-lateral strike-slip to east-vergent thrusting against the southern Death Valley fault zone. The resulting compression may have caused the shift in activity and the change in style of deformation along branches of the southern Death Valley fault zone.