--> Abstract: The Courthouse Syncline: A Gulf of Mexico-style Minibasin Exposed in the Paradox Basin, Utah, by M. R. Hudec and S. R. May; #90937 (1998).

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Abstract: The Courthouse Syncline: A Gulf of Mexico-style Minibasin Exposed in the Paradox Basin, Utah

HUDEC, MICHAEL R., Baylor University, and STEPHEN R. MAY, Exxon Production Research

The northwest-trending Courthouse Syncline is a major salt withdrawal feature in the northeastern portion of the Paradox Basin, Utah. The syncline extends for more than 50 km along strike, and forms the withdrawal basin between the salt-related Moab normal fault system to the southwest and the Salt Valley-Cache Valley salt wall to the northeast.

At the surface, the Courthouse syncline appears quite simple, plunging gently to the northwest with limb dips on the order of 6-15°. Seismic and well data, however, reveal a much more complicated story. Following Pennsylvanian deposition of the Paradox Formation salt, isopach patterns show that the syncline was the site of a salt high (which we name the Courthouse salt wall) during much of the Permian. The Courthouse wall had the same northwest trend as the present syncline, and covered a broad area, encompassing the location of the present Courthouse syncline as well as the Moab and Salt Valley-Cache

Valley structures on either side. During (inferred) late Permian time the crest of the Courthouse wall began to collapse, forming a minibasin (the Courthouse syncline) along its axis. The flanks of the Courthouse wall were not involved in the collapse, leaving the present-day Moab and Salt Valley-Cache Valley structures as relict highs on either side of the newly-formed basin. The Courthouse syncline is therefore in many ways a good structural analog for Gulf of Mexico slope minibasins, which form by subsidence into earlier-formed salt sheets.

Isopachs record that collapse was strongly asynchronous along the axis of the Courthouse salt wall. The southern end of the wall began to subside during late Permian time. Sedimentation then prograded northward along the axis of the structure, with the central portion of the syncline forming during the Triassic and the northern end not until some time in the Jurassic or Cretaceous.

AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah