Browsing by Author "Hauck, Tyler E."

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    Evidence of impact melting and post-impact decomposition of sedimentary target rocks from the Steen River impact structure, Alberta, Canada
    (2019) Walton, Erin L.; Timms, Nick E.; Hauck, Tyler E.; MacLagan, Ebberly A.; Herd, Christopher D. K.
    Hypervelocity bolide impacts deliver vast amounts of energy to the Earth's near surface. This crustal process almost universally includes sedimentary target rocks; however, their response to impact is poorly understood, in part because of complexities due to layering, pore space and the presence of volatiles that are difficult to model. The response of carbonates to bolide impact remains contentious, yet whether they melt or decompose and liberate gases by the reaction CaCO3(s) → CaO(s) + CO2(g)↑, has significant implications for post-impact climatic effects. We report on previously unknown carbonate impact melts at the Steen River impact structure, Canada, and the first description of naturally shocked barite, BaSO4. Carbonate melts are preserved as groundmass-supported calcite-rich clasts, sampled from an up to 164 m thick, continuous sequence of crater-fill polymict breccias. Electron microscopy reveals fluidal- and ocellar-textured calcite and barite, intimately associated with silicate melt, consistent with these phases being in the liquid state at the same time. Raman spectroscopy and electron backscatter diffraction (EBSD) mapping confirm the presence of high-pressure phases – reidite and coesite – within some Steen River carbonate melt-bearing breccias. These minerals attest to the strong shock provenance of the breccia and provide constraints on their shock history. Preservation of reidite lamellae in zircon indicates a shock pressure >30 GPa <60 GPa and temperatures <1473 K. In addition to melting, we present compelling evidence for widespread (70–100%) decomposition of carbonate target rocks, mixed as lithic clasts into hot impact breccias. In this context, decomposition occurs strictly post-impact due to thermal equilibration-related heating. We demonstrate that this mechanism for CO2 outgassing is likely more widespread than previously recognized. The presence of andradite-grossular garnet serve as mineralogical markers of decomposition, analogous to limestone-replacing skarn deposits. Ca-rich garnet may therefore prove an important indicator mineral for post-shock decomposition of carbonate-bearing target rocks at other craters. These findings significantly advance our understanding of how sedimentary rocks respond to hypervelocity impact, and have wide-reaching implications for estimating the amount and timing of climatically-active volatile release due to impact events.
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    Faults and associated karst collapse suggest conduits for fluid flow that influence hydraulic fracturing-induced seismicity
    (2018) Galloway, Elwyn; Hauck, Tyler E.; Corlett, Hilary; Pena, Dinu; Schultz, Ryan
    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.
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    Meteoric diagenesis and dedolomite fabrics in precursor primary dolomicrite in a mixed carbonate–evaporite system
    (2018) Hauck, Tyler E.; Corlett, Hilary; Grobe, Matthias; Walton, Erin L.; Sansjofre, Pierre
    Dedolomitization is a common diagenetic process in shallow burial environments and is often associated with sulphates in mixed carbonate-evaporite successions. In these settings, elevated Ca (super 2+) /Mg (super 2+) ratios necessary for dedolomitization result from the dissolution of sulphate phases by the incursion of undersaturated groundwater. Reported dedolomite textures from other studies are varied, but the most prevalent is a rhombic texture interpreted to result from the partial to complete pseudomorphic replacement of secondary dolomite rhombs formed in the burial diagenetic realm. In this study of primary cryptocrystalline to finely crystalline dolomicrites in the Prairie Evaporite Formation of north-eastern Alberta, dedolomitization has resulted in sutured to loosely packed mosaics of dedolomite that range from subhedral to distinctly euhedral (rhombic) crystal fabrics; however, no prior aggrading neomorphism producing dolomite rhombs is evident in the precursor dolomicrites. Non-pseudomorphic dedolomitization of the dolomicrites results in textures that include rhombic dedolomite crystals with cloudy cores comprising remnant dolomicrite and clear rims. These textures are similar to those observed in the pseudomorphic dedolomitization of secondary dolomite rhombs. The Prairie Evaporite Formation of north-eastern Alberta has experienced extensive karstification near the erosional margin of the sedimentary succession. Dedolomitization of dolomicrites occurs in marker beds within the Prairie Evaporite succession associated with evaporite karstification. Along with stratigraphic and petrographic considerations, stable isotope results support the interpretation of a shallow dedolomitization event influenced by meteoric waters derived from the basin margin. Negative delta (super 18) O and low delta (super 13) C values (averages of -13.6 ppm (sub VPDB) and 0.5 ppm (sub VPDB) , respectively) of the dedolomite, compared with those of the primary dolomicrite (averages of -6.0 ppm (sub VPDB) and 1.2 ppm (sub VPDB) , respectively), point to isotopically light diagenetic fluids. These results show that rhombic dedolomite textures can form through shallow, non-pseudomorphic dedolomitization of dolomicrites by meteoric fluids in the presence of sulphates, with resulting textures that are similar to the pseudomorphic dedolomitization of secondary dolomite rhombs.
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    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, Todd
    Given 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.