Orogenic pulses in the Alberta Rocky Mountains: Radiometric dating of major faults and comparison with the regional tectono-stratigraphic record

Abstract

Radiometric ages from regionally distributed thrust-fault gouge show that the eastward propagation of the southern Rocky Mountain fold-and-thrust belt inCanada occurred in four orogenic pulses that correlate with tectonic events of the Cordilleran interior and with depositional patterns in the adjacent foreland. In the Main Ranges, the Pyramid (163.0 Ma), Simpson Pass (161.7 Ma), and Johnson Creek (145.7 Ma) thrusts were related to the initiation of thinskinned deformation from Jurassic terrane accretion and were partly contemporaneous with development of the fi rst clastic wedge in the foreland basin. In the Front Ranges, the emplacement of the Greenock thrust (103.1 Ma) and Broadview-Snake Indian thrust (99.2 Ma) was contemporaneous with development of Cenomanian deltaic deposits in the immediate foreland. Three thrusts in the Front Ranges, Rocky Pass (74.8 Ma), Sulfur Mountain (75.6 Ma), and Clear water (74.2 Ma) thrusts, defi ne a Campanian phase of tectonic loading that led to the last major transgression in the southern portion of the Alberta foreland. Along the eastern margin of the Front Ranges, the McConnell thrust (54.0 Ma), together with the Muskeg (52.4 Ma), Brule (53.9 Ma), and Nikanassin (52.1 Ma) thrusts in the Foothills, recorded the last phase of regional contraction. The Late Jurassic, mid-Cretaceous, Late Cretaceous, and early Eocene deformation pulses are separated by relatively long periods (>40 m.y., >20 m.y., and >10 m.y.) of tectonic quiescence. These spatially and temporally restricted fault motion pulses contrast with gradual, forward fault propagation, while regional eastward progression of deformation is preserved. REGIONAL GEOLOGY ., 1983, Geochronology and tectonic implications of magmatism and metamorphism, southern Kootenay Arc and neighbouring regions, southeastern British Columbia: Part 1. Jurassic to mid-

A Late Jurassic to Early Cretaceous record of orogenic wedge evolution in the Western Interior basin, USA and Canada

“…In the case explored here, an episode of substantial sedimentation on the orogenic wedge during the Albian hypothetically would correspond to thrust movements in the orogen. In combination with late Albian-early Cenomanian cooling ages from thrust faults in the Canadian Rockies reported by Pana and Van der Pluijm (2015), the connection between wedge-top dynamics and foreland basin strata warrants further investigation. In this study, we provide key indirect evidence for significant Jurassic-Early Cretaceous wedge-top deposits in the Northern Cordillera foreland basin system.…”

Fault Slip and Exhumation History of the Willard Thrust Sheet, Sevier Fold‐Thrust Belt, Utah: Relations to Wedge Propagation, Hinterland Uplift, and Foreland Basin Sedimentation

“…The Sevier fold-thrust belt, which forms a key component of the North American Cordillera, is one of the best studied retroarc fold-thrust belts on Earth, and has served as a natural laboratory for seminal studies of thrust mechanics and kinematics (e.g., Boyer & Elliott, 1982;Hubbert & Rubey, 1959) and foreland basin evolution (e.g., DeCelles & Giles, 1996;Jordan, 1981). However, questions remain on thrust timing with possible shortening pulses, along-strike linkages of fault systems, and relations to changing plate margin dynamics (DeCelles & Coogan, 2006;DeCelles & Graham, 2015;Giallorenzo et al, 2018;Heller & Paola, 1989;Pana & van der Pluijm, 2015).…”

Deconvoluting complex structural histories archived in brittle fault zones

“…Moreover, some authors have successfully constrained the first-order time dimension of brittle deformation by 40 Ar/ 39 Ar and K-Ar dating of synkinematic mica/illite from brittle-ductile and brittle fault rocks789101112131415161718192021222324. Uncertainties, however, still remain as to the way to interpret these results, mostly reflecting the incomplete understanding of the mechanisms of clay crystallization and growth associated with the physical and chemical evolution of fault rocks.…”