Mike Hudec

Lecture MH1: Structural Style and evolution of thrust systems driven by spreading of allochthonous salt sheets

Thrust systems formed at the margins of spreading allochthonous salt sheets are almost unknown outside of the oil industry, but are interesting for three reasons. First, they are the chief mechanism for the advance of the Sigsbee salt canopy in the deepwater northern Gulf of Mexico, the largest salt structure on the planet. Second, they have a structural style quite different from toe-of-slope or tectonically driven fold-and-thrust belts. Finally, most are exquisitely imaged on seismic data, due to their marine setting and shallow depth of burial.

All sheet-margin thrust systems include a roof-edge thrust, which separates condensed stratigraphy in the salt-sheet roof from full-thickness strata on the surrounding peripheral plain. In some cases the roof-edge thrust is underlain by an imbricate wedge, an intensely deformed thrust pile that shortens sediments on the peripheral plain.

Although their geologic setting is utterly different, sheet-margin thrust systems show many geometric, kinematic, and dynamic similarities to better-known structures in oceanic trenches and foreland basins, and in front of advancing ice glaciers.

Hudec, M. R., and Jackson, M. P. A., 2007, Terra infirma: understanding salt tectonics: Earth-Science Reviews, v. 82, p. 1–24.

Hudec, M. R., and Jackson, M. P. A., 2006, Advance of allochthonous salt sheets in passive margins and orogens: AAPG Bulletin, v. 90, no. 10, p. 1535–1564. Also in Rowan, M. G., compiler, Getting started in salt tectonics: a compendium of influential papers, Getting Started Series No. 6.

Hudec, M. R., and Jackson, M. P. A., 2004, Regional restoration across the Kwanza Basin, Angola: salt tectonics triggered by repeated uplift of a metastable passive margin: AAPG Bulletin, v. 88, no. 7, p. 971–990.