Abstract: Three-Dimensional Development of the Northeastern Front Range, Colorado

The connection between oblique thrusting, conical folding, and basin development along the flanks of basement-cored foreland arches remains a fundamental problem with important implications to petroleum exploration. Recent outcrop studies in the northeastern Front Range of Colorado have uncovered a complex interplay of backthrusting and strike-slip faulting above a basement detachment which translated the range to the northeast during the Laramide orogeny. The proposed research will integrate surface information with well and seismic data to develop a three-dimensional model of the range margin.

Construction of balanced cross-sections and structure contour maps will enable 3-D balancing using new algorithms currently under development at CSU. Abundant well and seismic data from nearby oil fields are available to constrain interpretations of subsurface geometry. This research will test and refine 3-D balancing techniques which can be used to complement 3-D seismic data sets.

Initial results indicate radical changes in structural trends at the Front Range arch margin. The strike of thrust faults and trend of fold axes changes from northwest in the range to north-south in the basin. An "edge effect" that rotated the stress field toward an orientation orthogonal to the range front may have caused the deflection of structural trends. Fracture analysis utilizing excellent slickensided fault surfaces along east-west traverses from Precambrian to lower Cretaceous rocks will evaluate possible stress rotations. Understanding variations in the stress field will allow better predictions of fracture porosity within basement-involved petroleum reservoirs. 

AAPG Search and Discovery Article #90940©1997 AAPG Foundation Grants-in-Aid