Influence of lithosphere and basement properties on the stretching factor and development of extensional faults across the Otway Basin,southeast Australia |
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| Institution: | 1. School of Earth, Atmosphere and Environment, Monash University, Clayton, VIC 3800, Australia;2. Department of Earth Sciences, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands;3. Instituto Dom Luiz and Geology Department, University of Lisbon, Campo Grande, Lisbon, Portugal;1. Dipartimento di Biologia, Ecologia e Scienze della Terra, Università degli Studi della Calabria, Italy;2. Centro di Geologia e Amianto, Agenzia Regionale Protezione Ambiente Calabria, Italy;1. Applied Research in Ichnology and Sedimentology (ARISE) Group, Department of Earth Sciences, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada;2. Groundwater Resources Research Group (GRRG), Department of Earth Sciences, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada;3. Hemmera Envirochem Inc., 4730 Kingsway, Burnaby, British Columbia V5H 0C6, Canada;1. Geological Survey of Western Australia, 100 Plain St, East Perth, WA 6004, Australia;2. Australian Research Council Centre of Excellence for Core to Crust Fluid Systems, Department of Earth & Planetary Sciences, Macquarie University, NSW 2109, Australia;1. Huabei Oilfield Company of PetroChina, Renqiu, Hebei 062552, China;2. Key Laboratory of Petroleum Resource, Institute of Geology and Geophysics, Chinese Academy of Science, Beijing 100029, China;3. State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China;1. Department of Geological Sciences, Faculty of Science, Masaryk University, Kotlá?ská 2, 611 37 Brno, Czech Republic;2. Department of Geochemistry, Mineralogy and Petrography, Faculty of Sciences, University of Silesia, B?dzińska 60, 41-200 Sosnowiec, Poland;1. School of Earth and Environmental Sciences, University of Manchester, Williamson Building, Oxford Road, Manchester M13 9PL, UK;2. GEOMAR Helmholtz Centre for Ocean Research Kiel, Wischhofstr. 1-3, Kiel 24148, Germany |
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| Abstract: | The NW-SE striking Otway Basin in southeastern Australia is part of the continental rift system that formed during the separation of Australia from Antarctica. The development of this sedimentary basin occurred in two phases of Late Jurassic-Early Cretaceous and Late Cretaceous rifting. The evolution of this basin is mainly associated with extensional processes that took place in a pre-existing basement of Archean, Proterozoic to Paleozoic age. In this study, the total amounts of extension and stretching factor (β factor) have been measured for six transects across the entire passive margin of the Otway Basin region. The results show significant variation in extensional stretching along the basin, with the smallest stretching factors in the easternmost (β = 1.73, 1.9) and westernmost part of the basin (β = 2.09), and the largest stretching factors in the central part (β = 2.14 to 2.44). The domain with the lowest β factor is underlain mostly by thicker lithosphere of the Delamerian Orogen and older crustal fragments of the Selwyn Block. In contrast, the region with the largest β factor and amount of extension is related to younger and thinner lithosphere of the Lachlan Orogen. The main basement structures have been mapped throughout eastern South Australia and Victoria to examine the possible relationships between the younger pattern of extensional faults and the older basement fabrics. The pattern of normal faults varies considerably along onshore and offshore components of the Otway Basin from west to east. It appears that the orientation of pre-existing structures in the basement has some control on the geometry of the younger normal faults across the Otway Basin, but only in a limited number of places. In most areas the basement fabric has no control on the younger faulting pattern. Basement structure such as the north-south Coorong Shear Zone seems to affect the geometry of normal faults by changing their strike from E-W to NW-SE and also, in the easternmost part of the basin, the Bambra Fault changes the strike of normal faults from NW-SE to the NE-SW. Our results imply that the properties of the continental lithosphere exert a major influence on the β factor and amount of crustal extension but only a minor influence on the geometry of extensional faults. |
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| Keywords: | The Otway Basin Rifting Total amount of extension β factor Normal faults Lithosphere properties |
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