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This study includes the first set of muscovite, biotite, feldspar, and whole-rock 40Ar/39Ar ages from phyllonite belts of the Southern Rocky Mountain Trench (SRMT) and the western Rocky Mountain fold-thrust belt in the southern Canadian Cordillera. Eleven samples from the northern segment of the SRMT indicate two Early Cretaceous (135 and 125 Ma), two mid-Cretaceous (111 and 96 Ma), and two Late Cretaceous (85 and 75–72 Ma) peaks of transpressional tectonism and define the Southern Rocky Mountain shear zone. Four samples from the adjacent strike-slip Walker Creek fault zone yielded late Valanginian (133 Ma), early Aptian (124 Ma), and Albian-Cenomanian (111–96 Ma) ages, with Late Cretaceous (85–68 Ma) overprint. The oblique compression Bear Foot thrust (72 Ma) and its footwall, the Valemount strain zone, yielded consistent, late Campanian to earliest Maastrichtian plateau ages. Poorly recrystallized phyllonite samples from the Monarch, Moose Pass, and Chatter Creek thrust faults in the Rockies yielded ages consistent with a late Valanginian (134–131 Ma) tectonic event. The new structural and geochronological data indicate apparently distinct pulses of protracted orogen-parallel Cretaceous tectonism along the western margin of the Rockies and the eastern margin of the Omineca belt and document the kinematic link between the Foreland belt and its hinterland through a wide zone of transpression. These ages are also consistent with previously reported ages of thrusts in the Rockies accompanied by significant depositional changes in the foreland basin. The Early Cretaceous transpression (~135 and ~125 Ma) propagated into the western Rockies as previously unrecognized, out-of-sequence thrusting pulses that may have triggered the development of the forebulge responsible for the vast sub-Cadomin–sub-Manville unconformity in the foreland basin. [ABSTRACT FROM AUTHOR]

Recent discoveries of basement-hosted uranium deposits in the Patterson Lake corridor in the southwestern Athabasca Basin of Canada have brought vigorous exploration interest to the region. New lithostratigraphic constraints, geochronology and airborne geophysical surveys have dramatically improved the understanding of the host basement geology, warranting a re-examination of the remote predictive mapping and geophysical responses of the buried basement rocks. This study took a two-step approach to examine the regional basement geology and architecture. First, a mosaic of the long-wavelength response of potential field (gravity and magnetic) datasets was examined to divide the basement into regional domains based on bulk physical property variations. The interpretive geological model was then refined using textural and lineament analysis of new airborne gravity and magnetic datasets, geological drill hole logs and magnetic susceptibility measurements. The new basement map identifies and updates major features including a crustal-scale structure that separates the southern Tantato Domain from the newly defined eastern Taltson Domain. This structure may have played a role in localizing fluid flow in the Patterson Lake corridor, defining the spatial extents of structurally controlled buried felsic intrusions, and redefines the boundaries of the Taltson, Clearwater and Tantato Domains. In addition, the potential field enhancements delineated significant regional faults that controlled the geometry of Paleoproterozoic cover sequences and have implications for understanding the crustal architecture of the southern Rae Province. These new interpretations shed light on the tectonic history of the region to support on-going exploration activities and delineate regionally prospective areas in this understudied area of the Canadian Shield. Thematic collection: This article is part of the Uranium Fluid Pathways collection available at: https://www.lyellcollection.org/cc/uranium-fluid-pathways [ABSTRACT FROM AUTHOR]

During December 2011, a swarm of moderate-magnitude earthquakes was induced by hydraulic fracturing (HF) near Cardston, Alberta. Despite seismological associations linking these two processes, the hydrological and tectonic mechanisms involved remain unclear. In this study, we interpret a 3D reflection-seismic survey to delve into the geological factors related to these earthquakes. First, we document a basement-rooted fault on which the earthquake rupture occurred that extends above the targeted reservoir. Second, at the reservoir's stratigraphic level, anomalous subcircular features are recognized along the fault and are interpreted as resulting from fault-associated karst processes. These observations have implications for HF-induced seismicity, as they suggest hydraulic communication over a large (vertical) distance, reconciling the discrepancy between the culprit well trajectory and earthquake hypocenters. We speculate on how these newly identified geological factors could drive the sporadic appearance of induced seismicity and thus be utilized to avoid earthquake hazards. [ABSTRACT FROM AUTHOR]

Radiometric ages from regionally distributed thrust-fault gouge show that the eastward propagation of the southern Rocky Mountain fold-and-thrust belt in Canada 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 thin-skinned deformation from Jurassic terrane accretion and were partly contemporaneous with development of the first 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, define 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. [ABSTRACT FROM AUTHOR]