Upper Albian OAE 1d event in the Chihuahua Trough,New Mexico,U.S.A. |
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| Institution: | 1. Institut für Geologie, Leibniz Universität Hannover, Callinstraβe 30, 30167 Hannover, Germany;2. Institut de Physique du Globe de Strasbourg, EOST, Université de Strasbourg, 1 rue Blessig, 67084 Strasbourg Cedex, France;3. Institut für Geologie, Mineralogie und Geophysik, Ruhr-Universität Bochum, Universitätstrasse 150, 44801 Bochum, Germany;4. Department of Environment, Earth and Ecosystems, The Open University, Milton Keynes MK7 6AA, United Kingdom;5. Institut für Erd- und Umweltwissenschaften, Universität Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam-Golm, Germany;6. Institut de Géologie et Paléontologie, Université de Lausanne, Géopolis, 1015 Lausanne, Switzerland;1. Petroleum Geo-Services (PGS), 4 The Heights, Brooklands, Weybridge, Surrey KT13 0NY, United Kingdom;2. Department of Earth Science & Engineering, Imperial College, London SW7 2BP, United Kingdom;3. Faculty of Geology and Geoenvironment, University of Athens, Panepistimiopolis 15784, Athens, Greece;5. Earth Sciences Department, Reservoir Characterization Group, King Fahd University of Petroleum & Minerals, Dhahran 31261, Saudi Arabia;6. Department of Earth Science, University College London, Gower Street, London WC1E 6BT, United Kingdom;1. Department of Earth and Atmospheric Sciences, University of Nebraska–Lincoln, Lincoln, NE 68588-0340, USA;2. BugWare Oilfield Paleontology, 1615 Village Square Rd., Suite #8, Tallahassee, FL 32309, USA;1. Institute of Geological Sciences, Polish Academy of Sciences, Research Centre in Kraków, ul. Senacka 1, Kraków 31-002, Poland;2. Department of Geology and Paleontology, Faculty of Natural Sciences, Comenius University in Bratislava, Mlynská dolina, Ilkovi?ova 6, SK-842 15 Bratislava, Slovakia;3. Department of Geology and Paleontology, Natural History Museum of Geneva, 1 Rte de Malagnou, CP 6434, 1211 Geneva 6, Switzerland |
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| Abstract: | Oceanic anoxic events are clues to ocean processes and are correlation datums. In North America only OAE 1a and 2 are well documented. Based on a low-resolution sampling program, a multi-proxy geochemical approach constrained by a biostratigraphic framework was utilized to identify OAE 1d in the upper part of the upper Albian Mesilla Valley Formation near El Paso, Texas. Chronostratigraphic and biostratigraphic evidence indicate that the OAE 1d event in the Mesilla Valley section is located in the lower part of the upper Albian–Cenomanian Ovoidinium verrucosum zone, which correlates with the uppermost Albian Parathalmanninella appenninica and Stoliczkaia dispar zones. The chronostratigraphic age of the geochemical event in the Mesilla Valley Formation is uppermost Albian (97.39–97.30 Ma).The classic geochemical signatures for OAEs are enriched total organic carbon (TOC) concentrations and coupled positive δ13C excursions. OAE 1d at this location records TOC values ranging from 0.25 to 0.69 wt.% throughout the Mesilla Valley Formation, where TOC increases during the OAE (21.0–40.0 m) to more than 0.40 wt.%. Interestingly, the organic matter in the Mesilla Valley is dominantly type III, which indicates a pervasive terrigenous source. Although marine organic matter is abundant from the base into the middle of the proposed OAE interval, it is progressively replaced by terrestrial material above the OAE section during progradation. The δ13Corganic values record a positive δ13C shift of +1.6‰ from ?26.41 to ?24.80‰ across the stratigraphic interval from 21.0 to 40.0 m, which correlates with OAE 1d.Mn and Fe geochemistry suggest the depositional conditions of the Mesilla Valley Formation were dominated by anoxic and possibly Fe-rich bottom waters, specifically during the time period associated with the OAE 1d event. This interpretation is supported by the presence of Fe enrichment recorded by FeTotal/Al and FeHighly Reactive/FeT with the lack of Fepyrite/FeHighly Reactive associated with Mn depletion. |
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| Keywords: | Upper Albian OAE 1d Graphic correlation Carbon isotopes Sequential iron Chihuahua Trough |
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