TECTONICS AND RECONSTRUCTION OF MIDDLE MIOCENE TO RECENT RIFT BASINS IN NORTHEASTERN NEVADA
The second phase, ~7 Ma to ~ 3 Ma, is characterized by the cessation of extensional faulting and regional erosion followed by minor Pliocene (?) deposition of alluvial gravel that produced a marked angular unconformity with underlying Miocene basin fill. The third phase involved renewed extensional faulting responsible for the emergence of the modern basins and ranges, and erosion that destroyed or modified drainage divides established in the Miocene. By the third phase, northeast Nevada was a relative topographic high that was eroded into by the Humboldt, Snake River, and Thousand Springs (drains into the Great Salt Lake basin) fluvial systems. Headward erosion from these fluvial systems caused progressive erosion and exhumation of Miocene and Pliocene basinal strata as well as migration of extant Miocene drainage divides. Furthermore, encroachment of these fluvial systems into northeastern Nevada was driven by tectonic subsidence near the eastern and western margins of the Basin and Range Province and in the Snake River Plain in the wake of the Yellowstone hot spot to the north of northeastern Nevada.