Basin and Range Uplifts
East-west extension occurred during the Late Cenozoic Era within the Basin and Range province of North America. Faulting produced low and high-angle normal faults, generating several basins and volcanic activity throughout the region.
Two stages of extensional faulting are known to have occurred, large-scale extension during the Oligocene Epoch (about 23 to 33 million years ago) and smaller scale extension during the Miocene Epoch (about 5 to 23 million years ago).
The Basin and Range faulting tilted previous rock deposits along normal faults, producing the present-day topography and exposing much of the Paleozoic Era Alamo Impact deposits.