EXTENSIONAL BASIN FORMATION AND TILT-DOMAIN REVERSAL ASSOCIATED WITH REACTIVATION OF A THRUST RAMP, YUCCA FLAT, NYE COUNTY, NEVADA

Integration of geological and geophysical data from the Yucca Flat vicinity with regional tilt-domain analysis indicates that reactivation of the late Paleozoic to Mesozoic CP thrust fault during basin-and-range extension resulted in the formation of the Yucca Flat basin and a local reversal of the regional tilt-domain orientation. Magnetotelluric readings across Yucca Flat indicate that the CP thrust fault forms a steep east-dipping ramp structure beneath central Yucca Flat. The location of this ramp is coincident with the Carpetbag-Topgallant normal fault system, a major east-dipping, basin-forming fault system in Yucca Flat. Reactivation of the CP thrust ramp and formation of Yucca Flat during Neogene extension resulted in a west tilt to Cenozoic rocks beneath and adjacent to Yucca Flat. Analysis of stratal tilt in the region surrounding Yucca Flat shows that outside Yucca Flat most Cenozoic rocks dip eastward as a result of movement along major west-dipping normal faults.