The Silver Spring and Blackrock faults, east-central Nevada: Kinematics, timing, and role of low-angle normal faulting in the development of Railroad Valley

The structural development of Railroad Valley, a large and economically important Tertiary basin in east-central Nevada, has been the focus of much debate. This study addresses many of the points of controversy through a detailed geologic study of structures in the southwestern White Pine Range.; Detailed geologic mapping and construction of cross-sections reveal both low- and high-angle normal faults. The low-angle faults consist of three bedding-parallel faults, two top-to-the-southwest and one top-to-the-south, and two large displacement (>8 km heave) (26,000 ft) top-to-the-west detachments that denude a range-scale Mesozoic fold. Two spatially distinct groups of high-angle normal faults are present: (1) mostly synchronous faults in the hanging wall of the large-displacement detachments that developed in 3-D strain above non-planar footwalls; and (2) faults within the footwalls of the large-displacement detachments that indicate a counterclockwise rotation in extension direction from east-west to northwest-southeast though time.; A structural model is proposed for the southwestern White Pine Range where extension and uplift of the range begins in the Oligocene along low-angle faults, and in the Late Miocene, shifts to high-angle normal faulting. A regional comparison of geometries, kinematics, and timing of major detachment faults suggests that Railroad Valley developed as a result of several distinct structural systems, some of which are separated by transverse faults.