FORMATION OF DEATH VALLEY AND THE PANAMINT RANGE AS CONSEQUENCES OF STRIKE SLIP DEFORMATION WITHIN THE EAST CALIFORNIA SHEAR ZONE

Death Valley is a pull-apart basin formed within the East California Shear Zone. This dextral shear system is in turn part of the evolving Pacific-North America plate boundary, a 700-km wide deformation zone between the oceanic Pacific Plate and central/stable North America. The present topography of Death Valley (including 5 km of sediment) is here interpreted to be almost entirely due to formation of a pull-apart basin in the last 3 to 6 million years; the structural signature of earlier Basin and Range-style extension is preserved in exposed low-angle detachment fault systems in the Black Mountains and in the ‘Amargosa Chaos’ of the southern Black Mountains, but low-angle extension is not occurring today. There is also a detachment fault preserved in the Panamint Range on the west side of Death Valley. This fault is well-exposed at Mosaic Canyon at the north end of the range, where it forms a gouge zone at least 150 meters thick. This detachment fault can be traced southwards along the range almost to Telescope Peak, the highest point in the Panamint Range at 3368 meters. This elevation, the detachment fault and an overall symmetric topographic profile across the range (i.e. not like the asymmetry of a rotated fault block) suggest that the Panamint Range is also not a simple Basin and Range structure. Another relevant observation is that the Panamint Valley on the west side of the Panamint Range is not a deep pull-apart basin like Death Valley; young sediments are no more than a few hundred meters thick, suggesting limited fault control on formation of the valley. One tectonic scenario that can explain the structures and topography is that both Death Valley and the Panamint Range are formed by strike slip, Death Valley as a pull-apart and the Panamint Range as a large fold formed in a restraining bend within the overall strike slip deformation zone. This will be explored in this talk by incorporating GPS-derived velocity fields into an overall tectonic model for Death Valley and the Panamint Range.