North-South Compression of Rocky Mountain Foreland Structures: ABSTRACT

Gries, Robbie

doi:10.1306/03b59daa-16d1-11d7-8645000102c1865d

Cited by 3 publications

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“…Our flexural modeling results agree with this two-stage history of Laramide deformation by showing accelerated load height gain of the Laramide ranges during the early Eocene. We note here that Gries [1983] and Chapin and Cather [1983] also suggested a two-stage Laramide deformation model by examining the structure and sedimentation in the Colorado Plateau-Rocky Mountains area and suggested that the ranges striking N-S were uplifted earlier than the ranges striking W-E. Moreover, they suggested that the two-stage deformation was in response to a change in the subduction direction of the Farallon plate from eastward to northward.…”

Section: Implications For the Geodynamics Of Laramide Deformationsupporting

confidence: 56%

Southwestward weakening of Wyoming lithosphere during the Laramide orogeny

2016

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The mechanism of Laramide deformation in the central Rocky Mountains remains enigmatic. It is generally agreed that the deformation resulted from low‐angle subduction of the Farallon plate beneath the North American plate during the latest Cretaceous‐early Eocene; however, recent studies have suggested the importance of slab removal or slab rollback in causing this deformation. Here we infer Wyoming lithosphere structure and surface deformation pattern by conducting 2‐D flexural subsidence modeling in order to provide constraints on the mechanism of Laramide deformation. We assume that Wyoming lithosphere behaved as an infinite elastic plate subject to tectonic loading of mountain ranges and conduct 2‐D flexural subsidence modeling to major Laramide basins to document lithospheric stiffness and mountain load height. Our results show that the stiffness of Wyoming lithosphere varied slightly in each basin during the ~30 Myr duration of the Laramide deformation and decreased from northeastern Wyoming (Te = 32–46 km) to southwestern Wyoming (Te = 6–9 km). Our results also imply that the increase of equivalent load height of major Laramide ranges accelerated during the early Eocene. We propose that the bending stresses induced by the topographic load of the Sevier fold‐and‐thrust belt combined with crust‐mantle decoupling initiated by the overthickened Sevier hinterland and the end loads due to the low‐angle subduction at the western edge of the thick Wyoming craton have caused the southwestward decrease of lithospheric stiffness in Wyoming. Moreover, we attribute the accelerated load height gain during the early Eocene to both dynamic and isostatic effects associated with slab rollback.

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Section: Implications For the Geodynamics Of Laramide Deformationsupporting

confidence: 56%