Depositional model for a prograding oolitic wedge,Upper Jurassic,Iberian basin |
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| Institution: | 1. Université de Lorraine, CNRS, Lab. GeoRessources UMR 7359, BP 70239, 54506 Vandoeuvre-lès-Nancy Cedex, France;2. 256 R Alexandre André, 45240 Ligny Le Ribault, France;3. Chrono-Environnement Université de Franche-Comté, 16 route de Gray, 25030 Besançon cedex, France;4. Laboratoire de Géologie de Lyon, Terre, Planètes et Environnement, Université Claude Bernard Lyon 1 et Ecole Normale Supérieure de Lyon, 2 rue Raphaël Dubois, 69622 Villeurbanne Cedex, France;5. UMR 7517 EOST, Université Louis Pasteur, 1 rue Blessig, F 67084 Strasbourg Cedex, France;6. RCJ—Office de la culture, Paléontologie A16 Hôtel des Halles, Case postale 64, CH-2900 Porrentruy, Switzerland;7. Circuit de la Pierre Commercy ADCPE—Villasatel, Hameau des Carrières, 55 200 Euville, France;8. ANDRA DS/Milieu Géologique 1/7, rue Jean Monnet F, 92290 Châtenay-Malabry Cedex, France;9. SNSB-Bayerische Staatssammlung für Paläontologie und Geologie and GeoBioCenter LMU, Richard-Wagner-Str. 10, D-80333 München, Germany;1. Stratigraphy Group, School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK;2. Stratigraphy Group, School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester M13 9PL, UK;1. Dipartimento di Scienze della Terra, La Sapienza Università di Roma, P. Aldo Moro 5, I-00185 Roma, Italy;2. Istituto di Geologia Ambientale e Geoingegneria (IGAG) CNR, Sez. Sapienza, c/o Dipartimento Scienze della Terra, P. Aldo Moro 5, I-00185 Roma, Italy;1. Natural Sciences, National Museum of Wales, Cathays Park, Cardiff, CF10 3NP, UK;2. School of Earth and Ocean Sciences, Cardiff University, Park Place, Cardiff CF10 3AT, UK;3. Universidade de Lisboa, Faculdade de Ciências, Departamento de Geologia and Instituto Dom Luiz (IDL), Campo Grande, Ed. C6, 4° piso, 1749-016 Lisboa, Portugal |
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| Abstract: | Facies architecture and bedding patterns of the Kimmeridgian Pozuel Formation (Iberian Basin) evidence that this 50–70-m thick oolitic-grainstone unit conforms to the Infralittoral Prograding Wedge (ILPW) model instead of the classic models used for interpreting oolitic grainstones sandbodies on carbonate ramps or platforms (i.e., bank-margin shoal complexes, beaches and beach ridges).Ten lithofacies have been distinguished in the Pozuel Formation: 5–10° dipping clinobedded oolitic grainstone foresets passing to tabular oolitic packstones-grainstones, which interfinger the muddy basinal bottomsets. Landwards, the clinobeds pass into subhorizontal topsets composed of trough cross-bedded to structureless oolitic grainstones; oolitic-skeletal grainstones with stromatoporoids and coral-stromatoporoid-microbial mounds. Siliciclastic lithofacies and oncolitic/peloidal packstones occur at the innermost position. These lithofacies stack in strike elongated, 5–20-m thick, 0,5–2 km dip-oriented wide, aggradational-progradational packages with complex sigmoid-oblique geometries.Lithofacies, depositional geometries and stacking pattern permit to summarize the main characteristic of such Upper Jurassic oolitic infralittoral prograding wedge potentially to be applied in other oolitic sandbodies both in outcrops and subsurface: 1) sediment production within the wave action zone, 2) grainstone-dominated textures, 3) prograding basinward onto basinal muds, 4) laterally (strike) extensive, paralleling the shoreline, 5) variable thickness, commonly of few tens of meters, 6) broadly sigmoidal to oblique internal architecture, with topsets, foresets and bottomsets, 7) dip of foresets close to the angle of repose, 8) topsets deposited in shallow-water, extending through the shoreface, from the shoreline down to the wave base, 9) mounds, either microbial or skeletal, may occur in the topsets.The coated-grains factory was along the high-energy, wave-dominated outer platform (topset beds), from where the mud was winnowed and the grains transported both landward to the platform interior, and seaward to the platform edge, from were the grains cascaded down the slopes as grain flows and mass flows, forming clinobeds. This genetic model can be applied to other grain-dominated lithosomes, some of them forming hydrocarbon reservoirs, e.g., the Jurassic Hanifa Formation and some Arab-D (e.g., Qatif Field) in Arabia, the Smackover Formation in northern Louisiana and south Arkansas, the Aptian Shuaiba Formation (e.g., Bu Hasa Field) and the Cenomanian Mishrif Formation (e.g., Umm Adalkh Field) of the Arabian Gulf. |
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| Keywords: | Infralittoral prograding wedge Oolitic shoal Carbonate ramp Jurassic Bank-margin Clinobed |
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