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.

North-dipping, low-angle normal faults of the South Tibetan detachment system (STDS) are tectonically important features of the Himalayan-Tibetan orogenic system. The STDS is best exposed in the N-S-trending Rongbuk Valley in southern Tibet, where the primary strand of the systemthe Qomolangma detachmentcan be traced down dip from the summit of Everest for a distance of over 30 km. The metamorphic discontinuity across this detachment implies a large net displacement, with previous studies suggesting >200 km of slip. Here we refine those estimates through thermal-kinematic modeling of new (U-Th)/He and 40 Ar/ 39 Ar data from deformed footwall leucogranites. While previous studies focused on the early ductile history of deformation along the detachment, our data provide new insights regarding the brittle-ductile to brittle slip history. Thermal modeling results generated with the program QTQt indicate rapid, monotonic cooling from muscovite 40 Ar/ 39 Ar closure (ca. 15.4-14.4 Ma at ca. 490˚C) to zircon (U-Th)/He closure (ca. 14.3-11.0 Ma at ca. 200˚C), followed by slower cooling to apatite (U-Th)/He closure at ca. 9-8 Ma (at ca. 70˚C). Although previous work has suggested that ductile slip on the detachment lasted only until ca. 15.6 Ma, thermal-kinematic modeling of our new data suggests that rapid (ca. 3-4 km/Ma) tectonic exhumation by brittleductile to brittle fault slip continued to at least ca. 13.0 Ma. Much lower modeled exhumation rates (≤0.5 km/Ma) after ca.13 Ma are interpreted to reflect erosional denudation rather than tectonic exhumation. Projection of fault-related exhumation rates backward through time suggests total slip of ca. 61 to 289 km on the Qomolangma

The Darby Lake - Arrowsmith River area, southwest of Pelly Bay and southeast of Chantrey Inlet, is readily divided into three northeast-trending lithotectonic subdomains all of which are dominated by granitoid rocks, but contain uncommon, dispersed remnants of upper greenschist- to amphibolite-facies Archean supracrustal rocks dominated by psammite and semipelite with rare mafic and ultramafic units. Greenschist-facies supracrustal rocks are associated in the northwest and southeast by widespread tonalite, granodiorite, and monzogranite. Along the central axis of the map area, a wide range of moderately to strongly deformed, commonly L>S medium-grained to megacrystic granodiorite to dominant monzogranite tectonite bodies at amphibolite facies, grade into biotite±garnet and biotiteorthopyroxene± garnet-bearing granitoid rocks. These granitoid rocks all contain abundant screens, rafts, and schlieren of tonalite, biotite±garnet±hornblende±sillimanite-bearing metasedimentary rocks, and cospatial metasedimentary metatexite and diatexite. Small cupolas of massive biotite±magnetite monzogranite crosscut these rocks

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