Kinematics and Dynamics of Salt Tectonics  Driven by Progradation

Abstract

Scaled physical models illustrate the importance of progradation as a trigger for salt tectonics and formation of allochthonous sheets. Regional extension and contraction were excluded in the models. In our experiments, prograding wedges above a tabular, buoyant salt layer with a flat base expelled the salt basinward, forming the following structures proximally to distally: (1) sigmoidally distorted initially planar wedges, (2) relict salt pillows and salt welds, (3) basinward-dipping expulsion rollover and crestal graben, (4) rollover syncline, (5) landward-facing salt-cored monocline, and (6) distal inflated salt layer. This deformation zone amplified and advanced basinward during progradation; however, no diapiric salt structures formed. Over a buoyant salt layer whose basement had steps facing landward, progradation initially formed a broad anticline where salt flow was restricted across each basement step. Distal aggradation pinned the anticline and enhanced differential loading. The anticline actively pierced its crest, which ©Copyright 1997. The American Association of Petroleum Geologists. All rights reserved.1Manuscript received October 2, 1995; revised manuscript received May 9, 1996; final acceptance October 16, 1996. 2Bureau of Economic Geology, University of Texas at Austin, and Department of Geological Sciences, University of Texas at Austin, Austin, Texas 78713. 3Bureau of Economic Geology, University of Texas at Austin, Austin, Texas 78713. All modeling was done at the Applied Geodynamics Laboratory of the Bureau of Economic Geology, with financial support by grant number 3658-178 from the Texas Advanced Technology Program and from the following companies: Agip S.p.A, Amoco Production Company, Anadarko Petroleum Corporation, ARCO Exploration and Production Technology, BP Exploration, Chevron Petroleum Technology Company, Conoco and Dupont, Exxon Production Research Company, Louisiana Land and Exploration Company, Marathon Oil Company, Mobil Research and Development Corporation, Petroleo Brasileiro S.A., Phillips Petroleum Company, Societe Nationale Elf Aquitaine Production, Statoil, Texaco, and Total Minatome Corporation. The Department of Geological Sciences and the Geology Foundation at the University of Texas at Austin and Phillips Petroleum Company provided additional financial support for Hongxing Ge. Dan Schultz-Ela helped us depth convert and restore seismic sections. Mark Rowan, Mike Hudec, Lee Fairchild, Sharon Mosher, and Tucker Hentz provided invaluable suggestions for improving the paper. Publication authorized by the Director, Bureau of Economic Geology, University of Texas at Austin.