Growth faults at the prodelta to delta-front transition,Cretaceous Ferron sandstone,Utah |
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| Institution: | 1. Institute of Geophysics, Academy of Sciences of the Czech Republic, Bo?ní II/1401, Praha 4, Czech Republic;2. Department of Paleobiology, Smithsonian Institution, National Museum of Natural History, 10th & Constitution Avenue NW, Washington, D.C. 20560-0121, USA;3. Department of Earth & Planetary Sciences, Northwestern University, 2145 Sheridan Road Technological Institute, Evanston, IL, 60208, USA;4. Department of Geology and Geophysics, Yale University, New Haven, CT 06520, USA;5. Department of Geosciences, Boise State University, 1910 University Drive, Boise, USA;6. P.O. Box 231, Tropic, UT 84776, USA;7. Department of Earth Sciences, University of Adelaide, Adelaide, SA, Australia;8. Department of Botany, Trinity College Dublin, College Green, Dublin 2, Ireland;1. Department of Earth and Environmental Sciences, Vanderbilt University, 2301 Vanderbilt Place, Nashville, TN 37235-1805, USA;2. Smithsonian Institution, PO Box 37012, MRC 121, Washington, DC 20013-7012, USA;3. Department of Geological Sciences, Stanford University, 450 Serra Mall, Building 320, Room 118, Stanford, CA 94305-2115, USA;4. The Dinosaur Institute, Natural History Museum of Los Angeles County, 900 Exposition Blv., Los Angeles, CA 90007, USA;5. Department of Chemical and Physical Sciences, University of Toronto Mississauga, 3356 Mississauga Road North, Ontario L5L 1C6, Canada |
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| Abstract: | Cliff exposures of synsedimentary growth faults at the base of the Cretaceous Ferron sandstone in central Utah represent outcrop analogs to subsurface growth faults. Delta front sands prograded over and deformed less dense prodelta muds of the underlying Tununk Shale. Detailed fault patterns and associated facies changes demonstrate a complex fault history and style for growth fault development rather than a simple progressive development of faults in a basinward position. The most proximal and most distal fault sets were the earliest active faults. Growth faulting was initiated by deposition of cross-bedded distributary channel and mouth bar sandstones that reach 9 m thick in the hangingwalls of the faults. Curvature of the beds in the hangingwall of the faults nucleates smaller conjugate fault sets. Cross-bed sets in the hangingwalls of faults decrease from meter to decimeter scale away from the faults suggesting decreasing flow velocity or decreased preservation of cross sets as a result of decreasing accommodation in distal hangingwalls. Shifts in depositional loci, including upstream and downstream accretion of mouth bar sands contribute to the complex faults history and internal heterogeneity and development of potentially isolated sandy reservoir compartments. |
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