Vertical Axis Rotation Across the Eastern Mono Basin and West‐Central Walker Lane Revealed by Paleomagnetic Data From the Jack Springs Tuff

Abstract

AbstractThe mid‐Miocene Jack Springs Tuff (JST) outcrops from the Bodie Hills of eastern California into the western Mina Deflection, Nevada. Distal outcrops of the JST occur northwest of Mono Lake, CA, on a minimally rotated structural block. This provides a reference location for our paleomagnetic study to estimate relative vertical‐axis rotation. A new 40Ar/39Ar age places the eruption of the JST at 12.114 ± 0.006 Ma. Anisotropy of magnetic susceptibility data, once corrected for local tilt and vertical axis rotation, yields a mean imbrication that trends 178°. The probable source of the JST is located in the Huntoon Valley/Queens Valley region. Eighteen paleomagnetic sites constrain mid‐Miocene to recent vertical axis rotation within the region. All sites are discordant to the reference location with variable amounts of clockwise vertical axis rotation ranging from 25° to 104°. We hypothesize that a previously unrecognized early phase of deformation occurred that predates the deformation in the central Mina Deflection. These new data support the hypothesis that transtensional faulting associated with North American and Pacific plate interaction transferred deformation across the Mono Basin region that was partially accommodated by vertical axis rotation. By late Miocene, deformation had stepped east developing the Silver Peak‐Lone Mountain detachment system followed by the structures that presently define the central Mina deflection. This study further demonstrates that deformation occurred east of the Sierra Nevada Mountains at the latitude of the Mono Basin in western‐most Nevada, a region previously thought to be undeformed in terms of clockwise vertical axis rotation.