The Basin and Range Province is a classic locality of continental extension, and it is ideal for analyzing factors that control the collapse of thickened orogenic crust. However, the magnitude and distribution of extension, which are critical parameters for this analysis, remain poorly constrained in many areas. To address this problem, a cross section spanning the province at ∼39°N is presented. Retrodeformation yields 230 ± 42 km of cumulative extension (46% ± 8%), and an average pre-extensional thickness of 54 ± 6 km. When viewed at the scale of multiple ranges, two high-magnitude (∼60%−66%) and two low-magnitude (∼11%) domains of extension are apparent, and each can be related spatially to portions of the Cordilleran orogen that have high and low predicted crustal thickness, respectively. The eastern high-magnitude domain restores to a 60 ± 11 km thickness and corresponds to the western portion of the Sevier thrust belt and the estimated spatial extent of thick, underthrusted North American crust. The western high-magnitude domain restores to a 66 ± 5 km thickness and corresponds to the eastern part of the Sierran magmatic arc. Thickness variations inherited from Cordilleran orogenesis are interpreted as the primary control on extensional strain distribution. The eastern domain underwent a protracted, Late Cretaceous−Miocene transition to an extensional regime, while widespread extension in the western domain did not start until the Miocene, which is attributed to upper-crustal rheological differences between the granitic arc and the sedimentary section in the retroarc. Most extension can be temporally related to geodynamic driving events, including delamination, slab rollback, and plate-boundary reorganization, which caused gravitational collapse to proceed in distinct episodes.
Research Article|August 15, 2018
Geometry and magnitude of extension in the Basin and Range Province (39°N), Utah, Nevada, and California, USA: Constraints from a province-scale cross section
- Views Icon Views
Sean P. Long; Geometry and magnitude of extension in the Basin and Range Province (39°N), Utah, Nevada, and California, USA: Constraints from a province-scale cross section. GSA Bulletin doi: https://doi.org/10.1130/B31974.1
Download citation file:
- Share Icon Share