HOW THE PIECES ALL FIT TOGETHER: A STRUCTURAL INTERPRETATION OF THE CENTRAL BASIN AND RANGE
North-south striking extensional faults in the lower Colorado corridor are traced northward through the Muddy Mountains to the Mormon Mountains, crossing a collapsed east-west striking lateral ramp in the pre-existing Sevier thrust system. In the hanging wall of the detachment system, the ramp is expressed as the Las Vegas valley shear zone. The Lake Mead fault system is the same ramp exposed in the footwall. The Thumb basins formed through north directed collapse of the ramp and extend in a semi-circular arc from Yucca Mountain to the Virgin Mountains recording clockwise rotation during extension.
At a larger scale, the pre-existing Sevier thrust belt had a series of left-stepping lateral ramps along an oblique margin extending from Las Vegas into central Utah. The ramp structures were reactivated during extension and can be traced as accommodation zones across the modern Basin and Range. We interpret the Mina Deflection near Mono Lake as the continuation of the Las Vegas Valley lateral ramp. If so, the bend in the Klamath Mountains of northern California likely restores to the corner of the Colorado Plateau near Las Vegas and the Sierra Nevada likely collapsed off the Mogollon Rim in Arizona. To the north and east of Las Vegas, extension is accommodated on detachments that exhume the previously subducted western margin of North America. To the south and west displacement is accommodated on dextral strike slip faults such as the Furnace Creek and Walker Lane systems resulting from override of the Mendcino Transform and interaction with the Pacific plate.