Abstract Glaciogenic deposits in the Death Valley region occur within the Neoproterozoic Kingston Peak Formation (Fm.). In the Panamint Range, immediately west of Death Valley, the formation is as much as 1000 m thick and is continuously exposed for nearly 100 km along the strike of the range. Although the strata are variably metamorphosed and locally exhibit pronounced ductile strain, original sedimentary textures are well preserved in many places. Diamictite occurs in two distinct intervals, a lower one comprising the Limekiln Spring and Surprise members, and an upper one, the Wildrose Sub-member of the South Park Member. Lonestones, bullet-shaped and striated clasts, and rare dropstones within these members, along with the impressive lateral continuity of diamictic units, support a glacial origin. Both diamictic intervals are succeeded by well-defined carbonates, the oldest is the Sourdough Member of the Kingston Peak Fm. and the younger one is the Sentinel Peak Member of the overlying Noonday Dolomite. The stratigraphic succession between the Sourdough Member and the Wildrose Sub-member (i.e. the Middle Park, Mountain Girl and Thorndike sub-members of the South Park Member) is c. 300 m thick and includes lithologies recording deposition in braided fluvial to platform carbonate settings. Lithostratigraphic and chemostratigraphic profiles of δ 13 C for the Sourdough (–3‰ to +2‰, increasing upward) and Sentinel Peak (–3‰ ±1‰) members suggest correlation with, respectively, the older Cryogenian (commonly referred to as ‘Sturtian’ in previous literature) and younger Cryogenian (commonly referred to as ‘Marinoan’ in previous literature) cap-carbonate sequences recognized worldwide. Potentially economic uranium deposits (secondary brannerite) occur in graphitic schist of the Limekiln Spring Member and sub-economic uranium and thorium (hosted by detrital monazite) occur within quartz-pebble conglomerate in the South Park Member. The Kingston Peak Fm. strata in the Panamint Range contain no fossils, radiometric age control or primary magnetizations.

Abstract Recent studies, including structural mapping, stratigraphic and sedimentologic studies, geothermochronology, and geodetic measurements, have improved our understanding of the kinematics of Miocene to Recent deformation in the central Basin and Range. Based on reconstructions of rocks in the extensionally dismembered foreland and leading edge of the Sevier thrust belt, offset along the Las Vegas Valley shear zone, and on the provenance of a unique clast assemblage in proximal channel facies deposits at Frenchman Mountain, the southern and northern Lake Mead extensional domains have extended ~94 km and ~46 km, respectively. A compilation of >70 cooling ages from the Gold Butte crystalline block indicates that onset of this extension occurred at ~20 Ma, with rapid, large-magnitude extension beginning at ~15 Ma. In the Death Valley extended domain, studies of the provenance, depositional environment, and age of the Eagle Mountain Formation show that middle Miocene siliciclastic strata occurring in a northwest-trending belt from Chicago Valley to the Cottonwood Mountains were all deposited in an environment proximal to the Hunter Mountain batholith of the Cottonwood Mountains. This requires ~100 km of roughly southeast-northwest extensional and strike-slip displacement since ~11 Ma. Identification of extensionally dismembered Cenozoic structures, correlative with structures in the Cottonwood Mountains, Panamint Range, Bare Mountain, the CP Hills, and the Funeral Mountains, are also consistent with ~100 km of west-northwest extension across the Death Valley region .

We have reconstructed the isochron pattern of the Farallon and Vancouver plates in order to predict the thermal state and geometry of subducting slabs beneath western North America during the Cenozoic. Slabs do not last indefinitely; they warm up by conduction when bathed in the asthenosphere. As they warm up, they lose the ability to have earthquakes. Studies of modern subduction zones show that slabs become aseismic after a duration approximately equal to one-tenth their age upon subduction. Combined with a mathematical heat conduction model, these studies give us confidence that the thermal state of a slab can be characterized if we know the time since subduction and the age upon subduction. We reconstruct isochrons on subducted plates using the magnetic anomalies recorded in the Pacific plate, assuming symmetrical spreading and taking into account propagating rifts. Using the improved global plate reconstructions of Stock and Molnar (1988), we position the reconstructed plates with respect to North America to obtain maps of time since subduction and age upon subduction. The result is a series of maps of the slab geometry and approximate thermal condition at six times during the Cenozoic. With these maps we examine postulated relations between the presence and condition of the underlying slab and the occurrence of volcanism and tectonism in the overlying plate. We find that the very long flat slab proposed to have caused the Laramide Orogeny could have easily reached Colorado because of its fast average subduction rate and moderate age upon subduction, and because of the tendency for shallowly dipping slabs to last longer because they heat up more gradually while passing beneath the overriding plate. We find that the eastern edge of the proposed late Cenozoic “slab window” never existed, because of the young age of the slab. Instead, a region of effectively no slab gradually developed as early as 35 Ma, and it was farther inland than the proposed “slab window” Lacking an eastern edge, the “slab window” is better described as a “slab gap.” The southern boundary of the gap is diffuse, and its location is poorly constrained, whereas the northern edge is sharp and has clear, predictable geologic manifestations.