Department of Physical Sciences
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Browsing Department of Physical Sciences by Subject "Alberta"
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Item Anatomy of a young impact crater in Central Alberta: prospects for the ‘missing’ Holocene impact record(2008) Herd, Christopher D. K.; Froese, D. F.; Walton, Erin L.; Herd, E. P. K.; Duke, J.Small impact events recorded on the surface of Earth are significantly underrepresented based on expected magnitude-frequency relations. We report the discovery of a 36-m-diameter late Holocene impact crater located in a forested area near the town of Whitecourt, Alberta, Canada. Although undetectable using visible imagery, the presence of the crater is revealed using a bare-Earth digital elevation model obtained through airborne light detection and ranging (LiDAR). The target material comprises deglacial Quaternary sediments, with impact ejecta burying a late Holocene soil dated to ca. 1100 14C yr B.P. Most of the 74 iron meteorites (0.1–1196 g) recovered have an angular exterior morphology. These meteorites were buried at depths <25 cm and are interpreted to result from fragmentation of the original projectile mass, either at low altitude or during the impact event. Impact of the main mass formed the simple bowl-shaped impact structure associated with an ejecta blanket and crater fill. The increasing availability of LiDAR data for many terrestrial surfaces will serve as a useful tool in the discovery of additional small impact features.Item Subsurface faults inferred from reflection seismic, earthquakes, and sedimentological relationships: Implications for induced seismicity in Alberta, Canada(2018) Corlett, Hilary; Schultz, Ryan; Branscombe, Paulina; Hauck, Tyler E.; Haug, Kristine; MacCormack, Kelsey; Shipman, ToddGiven the recent induced seismic activity in Alberta, identification of subsurface faults and areas of structural complexity has become increasingly important in improving our understanding of the controls on induced seismic events. Using a 3D geological model supplemented with 2D and 3D reflection seismic data, several basement-bounded and basement-rooted faults, which extend upward and into the Devonian strata, are identified in areas coincident with increased seismic activity. The presence of faults in the study area was confirmed through a statistically significant correlation of high-quality seismic event data from historical and recent (1970–2016) induced earthquakes in Alberta to the edge of the Devonian-aged Swan Hills platform. Along with the identification of faults using reflection seismic and earthquake hypocenter data, a review of the role of pre-existing structure on depositional patterns that has been previously used to infer deep structure in this area, is also presented in this study. Several pre-existing extensional and/or transtensional style faults in the deeper strata and shallow basement of the study area are consistent with structure influencing the sedimentation of the overlying stratigraphy. Therefore, a better understanding of genetic fault-reef associations and the relationship to overlying strata may aid in identification of fault locations, style, and orientation. Considering the advancement of proper avoidance strategies during the planning stages of unconventional resource development or storage, this paper demonstrates the use of geological knowledge and relationships to identify areas comprising faults that may be prone to reactivation.Item Thermal metamorphic signature in melt-bearing polymict breccias from the Steen River Impact Structure, Canada(2015) Walton, Erin L.; Dence, Michael; Herd, Christopher D. K.Melt-bearing polymict breccia, similar to so called “crater suevite” described from Ries, has been documented from other small to medium size impact craters and those formed in mixed targets. This breccia type typically forms a volumetrically significant portion of allochthonous impactites; however, their mechanism(s) of formation is still debated, with recent studies calling on fuel-coolant interaction to explain certain characteristics. Detailed petrographic studies of these and related impactites can help to shed light on their genesis. In this study we describe a 127 m thick, remarkably uniform deposit of polymict breccia containing co-genetic impact melt clasts from the Steen River impact structure (SRIS) in NW Alberta, Canada.