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Tectonic evolution of a Laramide transverse structural zone: Sweetwater Arch, south central Wyoming
Author(s) -
Weil Arlo Brandon,
Yonkee Adolph,
Schultz Mary
Publication year - 2016
Publication title -
tectonics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.465
H-Index - 134
eISSN - 1944-9194
pISSN - 0278-7407
DOI - 10.1002/2016tc004122
Subject(s) - geology , seismology , echelon formation , clockwise , lineation , fold (higher order function) , fault (geology) , shear zone , precambrian , arch , tectonics , basement , geomorphology , paleontology , mechanical engineering , civil engineering , engineering
Abstract Structural, anisotropy of magnetic susceptibility (AMS), and paleomagnetic data record patterns of layer‐parallel shortening (LPS), vertical‐axis rotation, and regional fault‐fold evolution across the Sweetwater Arch, a major west to WNW trending, basement‐cored Laramide uplift in Wyoming. The southern arch flank is bounded by a WNW striking reverse fault zone that imbricated basement and cover rocks, the northern flank is bounded by a west striking fault zone with a component of strike‐slip and NW trending en echelon folds, and the eastern plunge transitions into an area of multiple‐trending faults and folds. Synorogenic strata record major arch uplift from Maastrichtian to Early Eocene time, followed by arch collapse. LPS, with development of systematic minor fault sets and AMS lineations, preceded large‐scale folding. LPS directions, estimated from both minor fault and AMS data, were oriented WSW along the northern flank, subparallel to Laramide regional shortening, but were refracted to the SSW along the southern flank, and to the west along the eastern arch plunge. Additional minor faults developed along steep fold limbs during continued shortening, with directions remaining SSW along the southern flank but becoming more variable along the eastern plunge where an increasingly heterogeneous stress field developed as additional faults were activated along basement heterogeneities. Vertical‐axis rotation was limited along the arch flanks, whereas the eastern plunge underwent counterclockwise rotation. Deflections in shortening directions were partly related to basement heterogeneities, including weak supracrustal belts on the arch flanks, a strong granitic core, and local reactivation of Precambrian shear zones.