--> Abstract: 3-D Structural Model of Basement-Involved Anticlines Along the Western Margin of the Bighorn Basin, Wyoming, by Subhotosh Banerjee and Shankar Mitra; #90078 (2008)

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3-D Structural Model of Basement-Involved Anticlines Along the Western Margin of the Bighorn Basin, Wyoming

Subhotosh Banerjee and Shankar Mitra
University of Oklahoma, Norman, OK

The western margin of the Bighorn basin, Wyoming, is marked by a series of basement-cored anticlines formed along steep, easterly-dipping reverse faults. These-second order anticlines, such as the Oregon Basin, Little Buffalo Basin, Grass Creek and Hamilton Dome anticlines, are characterized by short steeply-dipping forelimbs and long, gently-dipping back limbs. The cover rocks involved in the deformation consist of alternating clastic and carbonate sediments of Cambrian to late Cretaceous age above Precambrian granitic basement. Based on the 3-D modeling, these second-order structures are interpreted as back-limb structures on a first order anticline. Backlimb and forelimb dips of the second-order anticlines can be linked with the synclinal and anticlinal bends of backthrusts as well as with the structural position relative to the first-order structures. The Hamilton Dome and the Grass Creek anticlines show strong attenuation of Cretaceous shales along the forelimb. Structural thinning and stretching of the forelimb accommodates the displacement of the basement fault which is unexposed at the surface. Relatively smaller scale secondary detachment folds, which detach in the lower Cretaceous shales and Cretaceous Chugwater formation, are present in this area. These include several producing structures such as the Pitchfork, Spring Creek, North and South Sunshine fields, which produce from the Cretaceous Frontier, Permian Phosphoria, and Pennsylvanian Tensleep formations. Understanding the 3-D geometry of these basement-involved structures is critical in unraveling the structural evolution of the Bighorn Basin and in interpreting trap geometries in the Rocky Mountain Foreland basins.

 

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas