Calcite twinning strains associated with Laramide uplifts, Wyoming Province

John P. Craddock, David H. Malone, Alexandros Konstantinou, John Spruell, Ryan Porter

Research output: Chapter in Book/Report/Conference proceedingChapter

9 Scopus citations


We report the results of 167 calcite twinning strain analyses (131 limestones and 36 calcite veins, n = 7368 twin measurements) from the Teton-Gros Ventre (west; n = 21), Wind River (n = 43), Beartooth (n = 32), Bighorn (n = 32), and Black Hills (east; n = 11) Laramide uplifts. Country rock limestones record only a layer-parallel shortening (LPS) strain fabric in many orientations across the region. Synorogenic veins record both vein-parallel shortening (VPS) and vein-normal shortening (VNS) fabrics in many orientations. Twinning strain overprints were not observed in the limestone or vein samples in the supracrustal sedimentary veneer (i.e., drape folds), thereby suggesting that the deformation and uplift of Archean crystalline rocks that form Laramide structures were dominated by offset on faults in the Archean crystalline basement and associated shortening in the midcrust. The twinning strains in the pre-Sevier Jurassic Sundance Formation, in the frontal Prospect thrust of the Sevier belt, and in the distal (eastern) foreland preserve an LPS oriented approximately E-W. This LPS fabric is rotated in unique orientations in Laramide uplifts, suggesting that all but the Bighorn Mountains were uplifted by oblique-slip faults. Detailed field and twinning strain studies of drape folds identified second-order complexities, including: layer-parallel slip through the fold axis (Clarks Fork anticline), attenuation of the sedimentary section and fold axis rotation (Rattlesnake Mountain), rotation of the fold axis and LPS fabric (Derby Dome), and vertical rotations of the LPS fabric about a horizontal axis with 35% attenuation of the sedimentary section (eastern Bighorns). Regional cross sections (E-W) across the Laramide province have an excess of sedimentary veneer rocks that balance with displacement on a detachment at 30 km depth and perhaps along the Moho discontinuity at 40 km depth. Crustal volumes in the Wyoming Province balance when deformation in the western hinterland is included.

Original languageEnglish (US)
Title of host publicationSpecial Paper of the Geological Society of America
EditorsJ.P. Craddock, D.H. Malone, B.Z. Foreman, A. Konstantinou
PublisherGeological Society of America
Number of pages43
StatePublished - May 3 2022

Publication series

NameSpecial Paper of the Geological Society of America
ISSN (Print)0072-1077

ASJC Scopus subject areas

  • Geology


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