Tectonic and Stress Histories of the Piceance Creek Basin and the MWX Site from 75 Million Years Ago to the Present

摘要

Natural ractures in a given rock mass are the result of its integrated tectonic and stress histories. An extensive literature review, and analysis and interpretation of the compiled data, were conducted to derive a tectonic and stress history for the Piceance Creek Basin in northwestern Colorado. These histories create an empirical framework for theoretical modeling of the natural fractures in the Mesaverde Formation at the Department of Energy's Multiwell Experiment site. The fracture system at this site is similar to that exposed in these rocks in the nearby Grand Hogback. These fractures probably formed about 50 million years ago, within the east-west compressive field of the Sevier and Laramide orogenies and under the influence of high pore pressures and burial stresses. Subsequent episodes of deposition and tectonic activity produced several distinct sets of fractures in post-Mesaverde rocks, but Mesaverde fractures seem to have provided planes of weakness which were only reactivated, or unaffected, by these events. These events include late Laramide overthrusting of the White River Plateau westward into the basin, a possible brief reorientation of Laramide stresses to a north-northeast direction, and four uplift events of regional extent, during Oligocene and later time. 87 references, 2 figures, 1 table. (ERA citation 10:021930)