Evaluating the timing of hydrocarbon generation in the Devonian Duvernay Formation: paleomagnetic,rock magnetic and geochemical evidence |
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| Institution: | 1. State Key Laboratory of Biogeology and Environmental Geology, School of Earth Sciences, China University of Geosciences, Wuhan 430074, China;2. CAS Key Laboratory of Economic Stratigraphy and Palaeogeography, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China;3. Université de Lille, CNRS, UMR 8198 Evo-Eco-Paleo, F-59000 Lille, France;1. Université de Lorraine, CNRS, CREGU, GeoRessources, BP 70239, F-54506, Vand?uvre-lès-Nancy, France;2. ANDRA, 1-7 rue Jean Monnet,F-92268, Châtenay-Malabry, France;3. Géosciences Rennes, UMR 6118, Université Rennes 1 — CNRS, Campus de Beaulieu, F-35042, Rennes Cedex, France;4. Université de Nîmes, EA 7352 CHROME, rue du Dr Georges Salan, 30021 Nîmes, France;5. CRPG, 15 rue Notre Dame des Pauvres, F-54500, Vandoeuvre-lès-Nancy, France |
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| Abstract: | The physical and chemical changes associated with the thermal maturation of organic-rich shale have affected the paleomagnetic and rock magnetic characteristics of the Devonian Duvernay Formation in the Western Canada Sedimentary Basin. This formation has several lithofacies that correspond to deposition in platform, slope and deeper water settings under varied redox conditions. Shale, laminated mudstone and some massive mudstone facies show evidence of magnetic changes associated with maturation but wackestone, packstone and some massive mudstone facies appear to be unaffected by the process. Rock magnetic evidence suggests that thermal maturation induces a change in the magnetization carrier from magnetite and hematite to solely magnetite.The packstone and wackestone facies commonly show a reversed characteristic magnetization with a paleopole at 194°E, 70°N (A95=13.2) of Late Cretaceous-age. Shale and laminated mudstone facies in immature areas of the basin have inclination-only characteristic remanent magnetization (ChRM) means that range from 55 to 67 °C, requiring a pre-Cretaceous magnetization age. Shale and laminated mudstone facies in mature areas of the basin have a much steeper ChRM in direction ranging from 77 to 83 °C. Their very steep nature suggests that step demagnetization has not completely removed a drilling-induced remanence in some wells. |
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