Luncheon – Feburary 20, 2009

Title: An Integrated Model for the Evolution of the Northern Paradox Basin

Speaker: Bruce D. Trudgill, Department of Geology and Geological Engineering, Colorado School of Mines, Golden, Colorado

Date: February 20, 2009

Publication: The Outcrop, February 2009, p. 19, 22

The northern Paradox Basin is characterized by a variety of salt-related structures ranging from deeply buried salt pillows to faulted diapirs and salt walls exposed at the surface, which evolved as a result of crustal shortening, loading, creation of accommodation, differential sedimentation, and salt movement.

Seismic, well and published data define the proximal Cutler Group (Permian) as a basinward prograding unit that caused underlying salt within the Paradox Formation (Pennsylvanian) to flow in the same direction, i.e., towards the southwest. Sequential structural restorations indicate that the more proximal salt structures (e.g., the Onion Creek salt wall) evolved earlier than the more distal ones (e.g., the Moab salt wall). The degree of salt withdrawal was dependent on the amount of mobile salt available within the Paradox Formation, which varied with complex facies development across the basin.
The highest rates of sediment accumulation, salt wall growth, salt evacuation (in the welded areas), salt area decrease and subsidence occurred during Cutler time, when the Uncompahgre Uplift was most active. Using a foreland basin framework, a wedge-top zone is interpreted close or on top of the Uncompahgre Uplift, where post-depositional deformation and cannibalization reincorporated the overlying sediments into the active depositional regime. This new understanding of the salt system evolution in the northern Paradox basin impacts future oil exploration targets by defining a series of play concepts within the Paradox Formation, Honaker Trail Formation, Cutler Group (particularly the White Rim Sandstone).