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
1997. The American Association of Petroleum Geologists. All rights reserved.
received October 2, 1995; revised manuscript received May 9, 1996; final
acceptance October 16, 1996.
of Economic Geology, University of Texas at Austin, and Department of Geological
Sciences, University of Texas at Austin, Austin, Texas 78713.
of Economic Geology, University of Texas at Austin, Austin, Texas 78713.
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, Société 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.