The importance of missing strain in Deep Water Fold and Thrust Belts |
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| Institution: | 1. Basin Structure Group, School of Earth and Environment, University of Leeds, UK;2. Needham Geoscience Ltd., 10 Ghyll Wood, Ilkley, LS29 9NR, UK;3. Shell Global Solutions Netherlands, Rijswijk, The Netherlands;1. Energy Business Unit, Commonwealth Scientific and Industrial Research Organisation, Kensington, WA, Australia;2. Geoscience Australia, Canberra, ACT, Australia;3. Ophir Energy Plc, London, United Kingdom;4. Oceans & Atmosphere Business Unit, Commonwealth Scientific and Industrial Research Organisation, Hobart, TAS, Australia;5. Finder Exploration Pty Ltd, Perth, WA, Australia;1. Key Laboratory of Tectonics and Petroleum Resources, Ministry of Education, China University of Geosciences, Wuhan 430074, China;2. U.S. Geological Survey, Central Energy Resources Science Center, Denver, CO 80225, USA;3. Tianjin Branch of China National Offshore Oil Company Ltd, Tianjin 300452, China;4. State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Changping, Beijing 102249, China;5. Research Institute of Uranium Geology, Beijing 100029, China;1. Sapienza Università di Roma, Dipartimento Scienze della Terra, Piazzale Aldo Moro 5, Roma, Italy;2. Istituto di Geologia Ambientale e Geoingegneria (Consiglio Nazionale Delle Ricerche), Area Della Ricerca di Roma 1, Montelibretti, Via Salaria Km 29,300, Monterotondo (Roma), Italy;1. Departamento de Ingeniería Minera y Energética, Universidad de Huelva, La Rábida, Huelva 21819, Spain;2. CARBOZULIA, Avenida 2 No. 55-185, Casa Mene Grande, Maracaibo 4002 A, Venezuela;3. Postgrado de Geología Petrolera, Facultad de Ingeniería, Universidad del Zulia, Maracaibo 10482, Venezuela;4. PDVSA, Calle 77, Edificio PDVSA 5 de Julio, Maracaibo 4002, Venezuela;5. Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona, Barcelona 08028, Spain;1. Institut für Geowissenschaften, Universität Heidelberg, Im Neuenheimer Feld 234, 69120 Heidelberg, Germany;2. Benemérita Escuela Normal de Coahuila, Calzada de los Maestros s/n, Zona Centro, Saltillo, C.P. 25000, Coahuila, Mexico;3. Santa Engracia 257, Fracc. Santa Elena, Saltillo C.P. 25015, Coahuila, Mexico |
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| Abstract: | Deep water fold and thrust belts (DWFTBs) are sedimentary wedges that accommodate plate-scale deformation on both active and passive continental margins. Internally, these wedges consist of individual structures that strongly influence sediment dispersal, bathymetry and fluid migration. Most DWFTB studies investigate basin- and intra-wedge- scale processes using seismic reflection profiles, yet are inherently limited by seismic resolution. Of critical importance is strain distribution and its accommodation on discrete faults compared to distributed deformation. Recent studies have considered strain distribution by investigating regional reflection DWFTBs profiles within coupled systems, which contain down-dip compression and up-dip extension. There is broad agreement of a mis-balance in compression versus extension, with ～5% excess in the latter associated with horizontal compaction, yet this remains unproven.Using two exceptionally well exposed outcrops in the Spanish Pyrenees we consider deformation of DWFTB at a scale comparable to, and beyond, seismic resolution for the first time. By coupling outcrop observations (decametre to hectometre scale) with a re-evaluation of seismic profiles from the Orange Basin, South Africa, which contains one of the best imaged DWFTBs globally, we provide a unique insight into the deformation from metre to margin scale. Our observations reveal hitherto unrecognised second order structures that account for the majority of the previously recognised missing strain. This re-evaluation implies that ～5% missing strain should be accounted for in all DWFTBs, therefore existing studies using restorations of the sediment wedge will have underestimated crustal shortening in active margins, or sedimentary shortening in gravity driven systems by this amount. In contrast to previous studies, our observations imply that the majority of this strain is accommodated on discrete fault surfaces and this can explain the occurrence and location of a range of intra-wedge processes that are intimately linked to structures including sediment dispersal, fluid migration pathways and reservoir compartmentalisation. |
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| Keywords: | Deep water fold thrust belts Orange basin Pyrenee's: Sesimic interpretation Restorations: Gravity driven collapse DWFTBs"} {"#name":"keyword" "$":{"id":"kwrd0035"} "$$":[{"#name":"text" "_":"Deep water fold thrust belt |
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