Southwestward weakening of Wyoming lithosphere during the Laramide orogeny

Min Gao, Majie Fan, Robert Moucha

Research output: Research - peer-reviewArticle

Abstract

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.

LanguageEnglish (US)
Pages6219-6234
Number of pages16
JournalJournal of Geophysical Research
Volume121
Issue number8
DOIs
StatePublished - Aug 1 2016

Fingerprint

Laramide orogeny
lithosphere
stiffness
slab
Eocene
Stiffness
slabs
subsidence
subduction
mountain
basin
modeling
Subsidence
Loads (forces)
mountains
basins
North American plate
fold and thrust belt
craton
crust

Keywords

  • 2-D flexural subsidence
  • Laramide deformation
  • lithospheric stiffness
  • load height
  • low-angle subduction
  • slab rollback

ASJC Scopus subject areas

  • Geophysics
  • Oceanography
  • Forestry
  • Ecology
  • Aquatic Science
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology

Cite this

Southwestward weakening of Wyoming lithosphere during the Laramide orogeny. / Gao, Min; Fan, Majie; Moucha, Robert.

In: Journal of Geophysical Research, Vol. 121, No. 8, 01.08.2016, p. 6219-6234.

Research output: Research - peer-reviewArticle

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