A new TOC,Rock-Eval,and carbon isotope record of Lower Jurassic source rocks from the Slyne Basin,offshore Ireland |
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| Institution: | 1. Department of Petroleum Engineering, University of North Dakota, Grand Forks, ND 58202, United States;2. Core Laboratories, Reservoir Geology Group, 6316 Windfern Road, Houston, TX 77040, United States;1. MARE – Marine and Environmental Sciences Centre, Department of Earth Sciences, Faculty of Sciences and Technology, University of Coimbra, Portugal;2. iCRAG, Department of Geology, School of Natural Sciences, Trinity College Dublin, The University of Dublin, Ireland.;3. Departamento de Geología and Centro de Estudios Avanzados en Ciencias de la Tierra, Universidad de Jaén, Jaén, Spain;4. Department of Geology, Institute of Earth Sciences, Centre for Mathematical Sciences and Nature, Federal University of Rio de Janeiro, Brazil.;1. Department of Historical Geology and Paleontology, Faculty of Geology and Geoenvironment, National and Kapodistrian Univeristy of Athens, Panepistimiopolis, 15784 Athens, Greece;2. Laboratoire de Géologie de Lyon UMR 5276 CNRS, Université Lyon 1, ENS Lyon, Campus de la Doua, Bâtiment Géode, F-69622 Villeurbanne Cedex, France;3. Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, United Kingdom;1. Instituto Geológico y Minero de España (IGME), La Calera 1, 28770, Tres Cantos, Madrid, Spain;2. Departamento de Paleontología, Facultad de Ciencia Geológicas, Universidad Complutense de Madrid, 28040 Madrid, Spain;3. Instituto Geológico y Minero de España (IGME), Unidad territorial de Baleares, 07007 Palma de Mallorca, Spain |
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| Abstract: | This paper presents an integrated assessment of total organic carbon, Rock-Eval pyrolysis, carbonate δ13C and δ18O, and total organic carbon δ13C record of Upper Sinemurian–Aalenian age from the Slyne Basin (well 18/25-1), offshore Ireland. Total organic carbon (up to 5.2 wt%) and Rock-Eval pyrolysis data highlights the Portree Shale Formation Equivalent (Lower–?Middle Toarcian) as a mature (Tmax ～440 °C) source rock dominated by type II kerogens. This interval is more than 90 m thick.In a previously unexplored paleogeographical domain regarding stable carbon isotopes, the δ13C record shows positive values during the Upper Sinemurian, a negative trend followed by a minor positive trend during the uppermost Sinemurian–Lower Pliensbachian, a negative trend during the lowermost Lower Toarcian, and then the return to more positive δ13C values. Despite the biostratigraphic uncertainty, the coarse resolution of the dataset, and the complex assessment of diagenetic effects, we suggest that the δ13C record of the studied well records the Raricostatum Zone positive CIE, the Sinemurian-Pliensbachian Boundary Event, and the negative CIE associated with the T-OAE. The T-OAE positive CIE is not clearly defined in the obtained dataset. The slight post T-OAE negative CIE recovery to more positive values and the continuation of a relatively high organic content is coeval with a regional organic matter preservation interval observed in several Northern-European locations.These new datasets and their interpretation add to the understanding of the paleoenvironmental dynamics during the Early–?Middle Jurassic in the Northern European domain and opens new possibilities for hydrocarbon exploration in Ireland's offshore. |
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| Keywords: | Source rock Stable carbon isotopes Organic geochemistry Lower Jurassic Slyne Basin Offshore Ireland |
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