GSA Annual Meeting in Denver, Colorado, USA - 2016

Paper No. 64-3
Presentation Time: 9:00 AM-5:30 PM


PARKER, Stuart D., Structural Geology, University of Montana, 228 S 6th St W, Missoula, MT 59801 and ARENS, Shiva-Nandan, Geosciences, University of Montana, Missoula, MT 59801,

The extensional Basin and Range province experiences a discrepancy in extension magnitude and orientation across the eastern Snake River Plain (ESRP). The observed change in strain across the ESRP demands accommodation of some mechanism. High-angle conjugate normal faults paralleling the ESRP have long been attributed to crustal flexure, but are not capable of accommodating observed vertical offsets. This study proposes that these features accommodate the right-lateral motion observed within geodetic studies of the Centennial shear zone (CSZ)(Payne et al., 2013). Analogous features to those of the CSZ have been documented along the southern boundary of the ESRP and across the northern Basin and Range. This study uses the distribution, dimensions and orientations of pressure solution pits within clast-supported quartzite conglomerates in order to assess Neotectonic stress regimes within the northern Basin and Range and identify possible accommodation zones. Dimensions of documented pressure solution pits exceed those expected from overburden pressure alone and occur at surprisingly shallow depths, necessitating a tectonic stressor. A horizontal NE/SW maximum principal stress (σ1) orientation has been calculated for the CSZ as well as for other locations in the northern Basin and Range. This signature is consistent among distal sites and appears fixed since the late Neogene. These proposed transtensional accommodation zones help to balance the regional strain budget and reflect large-scale contemporary shear zones of the northern Basin and Range. Ongoing investigation of these accommodation zones is crucial to understanding the kinematics of the Basin and Range as well as the evolution of the ESRP and the Yellowstone volcanic system.