Late Cretaceous dynamics of the “Mojave Waistland,” California, USA | CU Experts

ABSTRACT; The Mojave Desert and surroundings occupy the narrowest segment of the retroarc part of the Late Cretaceous Cordilleran orogen. This chapter explores the consequences of focused contraction to frame a reexamination of the geology of the Mojave segment of the orogen. This intense shortening suggests that the arc and retroarc rose to higher elevations than other parts of the orogen. This led to considerable erosion as part of this area served as a sediment source for rivers heading north, southeast, and southwest. With increasing thickness, growing internal heat, and possibly removal of mantle lithosphere, profound extension drove substantial parts of the arc and retroarc westward over forearc and accretionary sedimentary rocks. The juxtaposition of granitoids with underlying oceanic-affinity schists (the so-called Pelona-Orocopia-Rand schists) was, in this conceptualization, due to large-displacement (100–200+ km) normal faulting accommodating the extension of this greatly thickened crust. This interpretation only requires minimal changes in subduction suitable for changes in the magmatic arc and so differs from hypotheses requiring profound changes in the subduction system, including the hypothesis of collision and subduction of an oceanic plateau sometimes thought to have been responsible for the Laramide orogeny.

VIVO