Energy balance for large thrust sheets and fault-bend folds |
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| Institution: | 1. General Delivery, 400 South Main Street, Riggins, ID, 83549, USA;2. Department of Geological Sciences, University of Florida, 241 Williamson Hall, Gainesville, FL 32611, USA;3. Department of Natural Sciences, University of Houston–Downtown, 1 Main Street, Suite N813, Houston, TX 77002, USA;4. Department of Math, Science, and Agriculture, North Arkansas College, 1515 Pioneer Drive, Harrison, Arkansas, 72601, USA;1. Centre for Earth Sciences, Indian Institute of Science, Bangalore 560012, India;2. Centre for Tectonics, Resources and Exploration, Department of Earth Sciences, University of Adelaide, SA 5005, Australia;3. School of Earth Sciences and Resources, China University of Geosciences Beijing, 29 Xueyuan Road, Beijing 100083, China;4. Department of Applied Geology, Curtin University, Bentley, WA 6102, Australia;5. Graduate School of Life and Environmental Sciences, University of Tsukuba, Ibaraki 305-8572, Japan;6. Department of Geology, University of Johannesburg, Auckland Park 2006, South Africa;7. Research Institute of Natural Sciences, Okayama University of Science, Okayama, Japan;8. Department of Geology, The University of Leicester, Leicester LE1 7RH, UK |
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| Abstract: | Thrust sheet movement over ramps requires energy because of the frictional resistance and deformation within the fault zone, fault-bend folding at the base and top of the ramp, and changes in the gravitational potential energy because of uplift. To model the energy usage, a kinematic model of a foreland thrust sheet is constructed assuming: (1) the ramp is planar and the flats are parallel to bedding; (2) the fault-bend folds are concentric; (3) thickness is preserved for beds that enter the folds parallel to the basal thrust fault and (4) cross-sectional area is preserved for rocks deformed by folding. Equations for the work done within the fault zone, and during uplift and fault-bend folding are derived by combining the kinematic model with stresses that increase in proportion to depth. The relative amounts of energy consumed by friction along the fault, uplift and fault-bend folding are estimated to be 2.7:1.0.25 for a ramp angle of 30°. The energy balance for the movement of large thrust sheets thus depends principally upon friction in the fault zone and changes in the gravitational energy. |
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