Variations in nappe-related fabric orientations during Paleoproterozoic ductile reworking of Archean basement, central Laramie Mountains, southeastern Wyoming

Archean granitic gneisses and supracrustal rocks in the central Laramie Mountains of southeastern Wyoming record several periods of Paleoproterozoic deformation. A large nappe structure, formed in response to westerly transport during the Trans-Hudson orogeny, produced large-scale recumbent to reclined folds that verge to the west. D2 deformational fabrics that formed during the nappe development are variably oriented within the nappe. These variations in orientation are due to regional and localized strain partitioning within the nappe and to reorientation of original nappe fabrics by younger D3 deformation associated with the Medicine Bow orogeny. The northern part of the study area contains a discontinuous zone of high strain, characterized by east-west trending D2 fabrics and localized zones of mylonitic textures in the granitic gneisses.; The variations in fabric orientations and associated strains can be generalized for three different parts of the nappe.; Local variations in fabric orientations are also the result of reorientation by younger Paleoproterozoic folds that trend southwest and verge to the southeast. (Abstract shortened by UMI.)...