Structural and tectonic evolution of the Douglas Creek arch, theDouglas Creek fault zone, and environs, northwestern Coloradoand northeastern Utah: Implications for petroleum accumulation inthe Piceance and Uinta basins

摘要

The Douglas Creek arch is a north–south-trending faulted anticline that separates the Uinta basin ofnortheastern Utah from the Piceance basin of northwestern Colorado. Previous work indicates that the archinitially formed during the Laramide orogeny as part of a broad, north–south-trending uplift that extendedfrom northwest Colorado into southern Wyoming and included the Rock Springs uplift. The axis of thisstructure was offset sinistrally and truncated by the late-Laramide uplift of the Uinta Mountains. This studyexamines available geologic, structure, Bouguer gravity, aeromagnetic, seismic, and paleomagnetic data toinvestigate this late-Laramide history, as well as indications of younger, post-Laramide tectonic events thathave shaped the Douglas Creek arch and environs. This study also uses the existing data to evaluate thegenetic relationships between Precambrian basement structures and shallower structures formed in the sedi-mentary cover.Results of this study suggest that a major east–west-oriented structure, the Douglas Creek fault, likelyhas a Precambrian ancestry and was reactivated during the Phanerozoic. Structures in the study area areconsistent with periodic sinistral slip, dominantly along the Douglas Creek fault, most recently during late-Laramide tectonic events. Northwest-striking fractures flanking the Douglas Creek arch and extending intothe surrounding basins are likely synthetic strike-slip faults related to a subsequent period of dextral slip onthe Douglas Creek fault. This deformation could be the result of the northwest translation of the ColoradoPlateau and opening of the Rio Grande rift during post-Laramide Tertiary extension.Wrench faulting has created enhanced permeability and numerous structural traps for petroleum accu-mulation across the Douglas Creek arch and in the surrounding basins. Wrench structures are identified bytheir distinct geometries, and the origins of their individual features can be discerned using supporting sub-surface data. Knowledge of the genesis of the wrench system allows for better understanding of wrench struc-tures and thus a better potential for success in the search for oil and gas.