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Mount, Van S.1, Thomas Griffith2, Garett Hodne2, John Byrd1 
(1) Anadarko Petroleum Corporation, Houston, TX 

ABSTRACT: Geometry, Kinematics and Exploration Implications of Basement-Involved Wedge Structures: Examples from the Southern Margin of the Hanna Basin, WY

Recent (2001-2) regional long offset (4.88 km) 2D seismic data across the southern margin of the Hanna Basin between the Rawlins Uplift and Simpson Ridge images excellent examples of basement-involved wedge structures generated during Late Cretaceous to Early Eocene Laramide deformation. In this area, the “deep” faults associated with wedge structures are SW-dipping, basement-involved reverse faults which uplift the northern portion of the Sierra Madre and Medicine Bow Mountains. The deep SW-dipping basement faults cut up-section through competent basement through Lower Cretaceous strata, ultimately merging with “shallow” NE-dipping reverse faults within the incompetent Upper Cretaceous Steele Shale Formation. Deformation associated with displacement over the “shallow” NE-dipping faults generates the Saint Mary’s Ridge and Dana Ridge fault-propagation fold structures. Displacements on the deep and shallow fault systems track each other along strike such that the point where displacement on the deep SW-dipping fault systems decreases to zero directly underlies the lateral terminations of structures associated with the shallow, NE-dipping fault systems. 
Wedge structures can include large trap volumes and have significant implications for exploration strategies. The deep basement-involved and shallow detached-faults commonly intersect within a shale-prone or ductile stratigraphic interval. The detachment interval may not only serve as an effective source rock for the overlying structure, but also as a seal and source for juxtaposed reservoirs below the detachment.

 

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.