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Upper Paleozoic strata in the eastern Richardson Mountains, northern Mackenzie Mountains and Peel Plateau of the Yukon consist of basinal sediments overlain by a siliciclastic sedimentary wedge derived from the Late Devonian Ellesmerian orogeny. Unconformably overlying Paleozoic strata in the Peel Plateau are Cretaceous sedimentary rocks that were deposited in the foreland basin of the Cretaceous Cordilleran orogeny. This study, as part of the interdisciplinary “Regional Geoscience Studies and Petroleum Potential, Peel Plateau and Plain” project, examines the sedimentology, stratigraphy and hydrocarbon potential of Upper Paleozoic strata in the Peel region and adjacent Richardson and Mackenzie mountains. Units investigated as part of this study include the Canol (Upper Devonian), Imperial (Upper Devonian) and Tuttle (Upper Devonian-Lower Carboniferous) formations, ‘Cf’ map unit (?Upper Devonian-Lower Carboniferous), and ‘Mo’ map unit (?Upper Devonian-Lower Carboniferous). Preliminary analyses suggest the Canol, Imperial, Tuttle, ‘Cf’ and ‘Mo’ are potential hydrocarbon source rocks for the region. The Tuttle Formation is the best prospective reservoir rock of the Upper Paleozoic strata.

The Eagle Plain basin, having proven hydrocarbon potential, is a relatively underexplored intermontane basin located in northern Yukon . Previous studies of the middle Albian-Cenomanian Parkin Formation and the Turonian Fishing Branch Formation are based on broad lithostratigraphic correlations. The primary goal of the study is to refine the sequence stratigraphic framework of the middle to Upper Cretaceous succession based on sedimentological observations. New findings from this study require subdivision of the stratigraphic nomenclature by defining new informal lithological members. Facies transitions, paleoflow indicators and isopach maps indicate overall westward deepening of the basin. Large-scale, sand-prone mass transport deposits observed in the upper part of the lower Parkin shale member in western Eagle Plain indicate the presence of shelf-to-basin floor relief of at least 100 m. Recognition of significant shelf-to-basin floor topography greatly increases the potential for hydrocarbon reservoirs (gas-dominated) in stratigraphic traps associated with the shelf edge.

The Peel Plateau and Plain in Yukon is a potentially prospective petroleum province that lies north of the Mackenzie Mountains and east of the Richardson Mountains up to the inter-territorial boundary. The area contains a Lower Cambrian to Upper Cretaceous stratigraphic succession up to approximately 4.5 km thick. Nineteen exploratory wells have been drilled within the region without economic reserves or production, but with some petroleum shows. A probablilistic petroleum resource assessment suggests that there is a significant potential for natural gas throughout the region. In general, petroleum potential is inferred to decrease both westward, and with increasing depth and stratigraphic age. The small size of gas pools will be an impediment to their development because of their location. No crude oil potential can be estimated due to an inferred lack of oil-prone sources in strata of suitable maturity. Where previous work speculated that the history of petroleum systems in the Peel Plateau and Plain was distinctive from that of surrounding regions that are suitably characterized, this work finds no justification for such a distinctive petroleum system history. The resulting undiscovered potential is, therefore, considered to be consistent with the results of the exploration history.

An evaluation of hydrocarbon resource potential in Eagle Plain is one aspect of the Yukon Sedimentary Basins Project, a five-year (2008-2013), collaborative Geo-Mapping for Energy and Minerals (GEM) Program of the Geological Survey of Canada (GSC), in partnership with the territorial governments and universities. As part of this project, Yukon Geological Survey (YGS) and Northern Cross (Yukon) Limited (NCY) are collaborating with the GSC to assess shale gas potential of Devonian shale at Eagle Plain. Diamond drill core was retrieved from mineral exploration properties to evaluate shale gas potential of Devonian shale of Road River Group and Canol and Imperial formations. Diamond drill core from four holes, located on the Rich property east of Eagle Plain Hotel, were examined and sampled. The core was systematically sampled and analysed by Rock-Eval pyrolysis, optical microscopy, X-ray diffraction (XRD) mineralogy, and palynology. The results indicate that the succession is thermally overmature with respect to hydrocarbon generation. Due to the high levels of thermal maturity, the Rock-Eval data are unreliable. However, high amounts of residual organic carbon suggest that the Canol Formation has the potential to be an important source rock in the region, under favourable burial conditions. The very high level of thermal maturity of the strata also resulted in very few identifiable Palynomorphs; however, Canol and Imperial formation samples yielded dates of Middle to Late Devonian and Frasnian to Famennian, respectively. XRD analyses indicate Canol Formation shale is highly siliceous whereas Road River Group shale and silty shale of the Imperial Formation are less siliceous and exhibit a more varied lithology. This study suggests that the Canol Formation is more prospective for shale gas than strata of the Imperial Formation or Road River Group.

The Upper Devonian to Lower Carboniferous Tuttle Formation was an exploration target for oil and gas in the Peel Plateau and Eagle Plain in the 1960s and 1970s. To date, seven minor gas shows have been identified in the Tuttle Formation in the Peel region. This study is part of a long-term project to investigate the sedimentology, stratigraphy and hydrocarbon potential of this unit in the Peel region. The Tuttle Formation forms the upper part of a siliciclastic wedge that was deposited in the foreland basin of the Yukon and Ellesmerian fold belts. In the eastern Richardson Mountains, on Trail and Road rivers, it occurs as alternating packages of resistant and recessive intervals. Resistant intervals, 23 to 54 m thick, comprise five lithofacies including fining-upward sandstone, massive sandstone, siltstone, conglomerate and diamictite. Recessive intervals, 55 and 144 m thick, consist of siltstone and shale and are mostly covered.

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A copy of this thesis is available at the EMR library – QE446.Y8 H94.