Basin genesis associated with strike‐slip faulting in the Basin and Range, southeastern Nevada

Abstract

The structural nature of two prominent Basin and Range strike‐slip systems, the Lake Mead fault system and the Las Vegas Valley shear zone, are examined using both geological field mapping and geophysical surveys at various scales. The intent of this study is to document deformation directly attributable to strike‐slip faulting with an emphasis on basin genesis. Our field study of the Lake Mead fault system reveals a major left step in the system. The stepover results in the genesis of a 2‐km‐deep pull‐apart, the Overton Arm Basin, consistent with the kinematics and mechanics of strike‐slip faulting. Having established the origin of the Overton Arm basin as a strike‐slip‐related pull‐apart basin, the geometry of poorly exposed strike‐slip systems can be revealed by understanding the related basins along their length. One such system, the Las Vegas Valley shear zone, is shown with the aid of geophysical data to be geographically related to three distinct en echelon basins. When these basins are interpreted as pull‐apart basins, the geometry of the Las Vegas Valley shear zone becomes apparent for the first time. We assert that strike‐slip faulting in southeastern Nevada is a deformational mechanism that contributes locally to the regional extensional tectonics. Such an interpretation modifies extant models that treat strike‐slip faults in rifted terrains as passive lateral boundaries that simply accommodate extension without contributing to the process.