Browsing by Author "MacCormack, Kelsey"
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Item Clinoform identification and correlation in fine‐grained sediments: a case study using the Triassic Montney Formation(2018) Playter, Tiffany; Corlett, Hilary; Konhauser, Kurt; Robbins, Leslie; Rohais, Sebastien; Crombez, Vincent; MacCormack, Kelsey; Rokosh, Dean; Prenoslo, Donald; Furlong, Carolyn M.; Pawlowicz, John; Gingras, Murray K.; Lalonde, Stefan; Lyster, Steven; Zonneveld, John-PaulStratigraphic correlation of fine-grained successions is not always straightforward. Complicating factors, such as unconformities, structural complexity, subsidence and especially minimal grain-size variation, make the application of traditional correlation methods to fine-grained successions problematic. Alternatively, the analysis of detailed geochemical data can allow for the determination of variations in sediment provenance, mineralogy, detrital flux and hydrothermal input. When compared with modelled clay input over time, these geochemical indicators can be used to determine changes in relative sea-level and palaeoclimate, allowing for the identification of clinoform surfaces. As an example, this study outlines detailed correlations of chemostratigraphic packages within the lower Triassic Montney Formation in Western Canada to demonstrate the effectiveness of chemostratigraphy in defining and correlating fine-grained clinoforms across a sedimentary basin. The data set used includes five wells and one outcrop succession, from which geochemical profiles were generated and tied directly to mineralogical data and well logs. These analyses reveal 13 distinct chemostratigraphic packages that correlate across the basin. Observed elemental and inferred mineralogical changes highlight trends in relative sea-level and palaeoclimate, as well as episodes of inferred hydrothermal input to the Montney basin. Cross-plots of La/Sm and Yb/Sm further suggest hydrothermal input as well as the scavenging of middle rare earth elements by phosphatic fish debris. Additionally, plots of La/Sm versus Yb/Sm, which show volcanic arc input within the Doig Formation, suggest an additional sediment source from the west during the Anisian. Pairing detrital and clay proxies demonstrates changes in relative sea-level and, at the Smithian/Spathian boundary, the lowest relative sea-level in the Montney Formation is observed, corresponding to a change in climate.Item Linking fossil reefs with earthquakes: geologic insight to where induced seismicity occurs in Alberta(2016) Schultz, Ryan; Corlett, Hilary; Haug, Kristine; Kocon, Ken; MacCormack, Kelsey; Stern, Virginia; Shipman, ToddRecently, a significant increase in North American, midcontinent earthquakes has been associated with contemporaneous development of petroleum resources. Despite the proliferation of drilling throughout sedimentary basins worldwide, earthquakes are only induced at a small fraction of wells. In this study, we focus on cases of induced seismicity where high-resolution data are available in the central Western Canada Sedimentary Basin. Our regional comparison of induced earthquake depths suggests basement-controlled tectonics. Complementary to these findings, hypocenters of induced seismicity clusters coincide with the margins of Devonian carbonate reefs. We interpret this spatial correspondence as the result of geographically biased activation potential, possibly as a consequence of reef nucleation preference to paleobathymetric highs associated with Precambrian basement tectonics. This finding demonstrates the importance of geologic/tectonic factors to earthquake induction, in addition to industrial operational parameters. In fact, the observation of induced seismicity silhouetting deep fossil reef systems may be a useful tool to identify future regions with increased seismogenic potential.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.