Structural Controls on Detachment Folds Associated with Foreland Arches: Beaver Creek Anticline, Wyoming

Sara Smaltz
Colorado State University, Department of Geosciences Fort Collins, CO 80523
[email protected]

     Of the smaller, second-order anticlines adjacent to basement arches in the Rocky Mountains, the detachment folds basin-ward of basement-cored monoclines bounding the arches are the least well known due to their common coverage by synorogenic strata. These anticlines host important hydrocarbon reserves and provide the best prospects for undiscovered fields. This study will address the controls on these detachment folds by documenting the geometry and kinematics of a second-order detachment fold using excellent surface exposures of Beaver Creek Anticline, which is located on the western edge of the Bighorn Mountains. Laramide slip and paleostress directions will be determined by analyzing the kinematic data such as minor fault and fracture orientations that I have collected. These data will be compared to structural variables to determine controls on fracture orientation and density. Slip direction data will be used to determine the appropriate orientations for serial 2D cross-sections and to help test kinematic hypotheses. 2D cross-sections parallel and perpendicular to fault slip data will include well and map data and will be used to extrapolate the Beaver Creek detachment system into the subsurface. These cross-sections will be combined with fault slip data to create a 3D model of the Beaver Creek detachment system using 3DMove. The model will be restored using line length balancing and flexural flattening to help characterize strain in the area and further test interpretations. The final results may aid in future development of existing reservoirs and recognition of similar structures with important hydrocarbon reserves.

AAPG Search and Discovery Article #90070 © 2007 AAPG Foundation Grants in Aid