Origin Of Transverse Folds In An Extensional Growth-Fault Setting: Evidence From An Extensive Seismic Volume In The Western Gulf Of Mexico

Marine and Petroleum Geology 27 (2010) 1494e1507

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Marine and Petroleum Geology
journal homepage: www.elsevier.com/locate/marpetgeo

Origin of transverse folds in an extensional growth-fault setting: Evidence from an extensive seismic volume in the western Gulf of Mexico
Angela McDonnell*, Martin P.A. Jackson, Michael R. Hudec
Bureau of EconomicGeology, Jackson School of Geosciences, The University of Texas at Austin, Austin, TX 78713-8924, USA

a r t i c l e i n f o
Article history: Received 20 August 2009 Received in revised form 24 February 2010 Accepted 5 March 2010 Available online 15 March 2010 Keywords: Growth fault Transverse trend Corrugations Hanging-wall deformation Salt evacuation

a b s t r a c t
Growth faults ingravity-driven extensional provinces are dominated by coast-parallel trends, but coastperpendicular (transverse) trends are far less documented. The ClementeeTomas fault in the inner Texas shelf has corrugations that are transverse to the fault and that plunge downdip. A large (8500 km2), highquality, 3D seismic survey allows a uniquely encompassing perspective into hanging-wall deformation above thiscorrugated fault surface. Synextensional strata in the hanging wall are folded into alternating transverse ridges and synclines, typically spaced 10 km apart. Forward modelling in dip profiles of an extensional fault having three ramps produces ramp basin-rollover pairs that compare with the seismically revealed ridges and synclines. As they translated down the undulose fault plane, ramp basins androllovers were juxtaposed along strike, forming the hanging-wall ridges and synclines observed offshore Texas. Fault-surface corrugations correlate broadly with footwall structure. We infer that corrugations on the ClementeeTomas fault formed by evacuation of an allochthonous salt canopy emplaced in the late Eocene to early Oligocene. Early salt evacuation (Oligocene) created an undulosetopography that influenced incipient Clemente-Tomas fault segments as they merged to form an inherently undulose fault. Late salt evacuation (early Miocene) further deformed this fault surface. Ó 2010 Elsevier Ltd. All rights reserved.

1. Introduction Listric fault systems form in various extensional settings including (1) gravity-driven deltaic systems such as the Gulf of Mexico (Worrall and Snelson,1989; Watkins et al., 1996); the Niger Delta (Evamy et al., 1978; Doust and Omatsola, 1990); offshore Brunei (Imber et al., 2003; Back et al., 2005); the Bight Basin, Australia (Totterdell and Krassay, 2003); and the Nile Delta (Beach and Trayner, 1991) and (2) continental extensional systems such as the Basin and Range province (Hamilton, 1987). Folds in the hanging walls of extensional faultstypically trend parallel to the strike of the master fault, but they can also be transverse (orthogonal or perpendicular) to the master fault. Studies show that rollover folds in the hanging wall are strongly controlled by varying shape of the master fault along strike and downdip (Gibbs, 1983; White et al., 1986; Groshong, 1989; Dula, 1991; White and Yielding, 1991; Kerr and White, 1992; Xiao andSuppe, 1992; Withjack and Peterson, 1993; Withjack and Schlische, 2006). Experiments with wet clay (Cloos, 1968; Withjack et al., 1995) or dry sand (McClay and Ellis, 1987; McClay and Scott, 1991) simulated hanging-wall deformation on nonplanar normal faults.

* Corresponding author. E-mail address: angela.mcdonnell@beg.utexas.edu (A. McDonnell). 0264-8172/$ e see front matter Ó 2010 Elsevier Ltd.All rights reserved. doi:10.1016/j.marpetgeo.2010.03.006

Kinematic studies examined how fault shape, fault displacement, and depositional patterns affect hanging-wall structures (White et al., 1986; Dula, 1991; Kerr and White, 1992; Xiao and Suppe, 1992; Withjack and Peterson, 1993). Both kinematic and experimental models have simulated fault-bend folds above concave-up, convexup, and...