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The Structural Evolution of Hamilton Creek/Dry Creek Anticline and Its Relationship to the Southeast Termination of Paradox Valley, SW Colorado

Abstract

The Hamilton Creek/Dry Creek anticline is a salt-cored structure in the northeastern part of the Paradox Basin, ~ 20 km southwest of the basin-bounding Uncompahgre Front. Integration of subsurface well data, 2D and 3D seismic datasets, gravity data, and field data collected across the core of the exposed Dry Creek anticline provide a more comprehensive understanding the structural evolution of this structure, with relation to the larger Paradox Valley salt wall to the northwest. On seismic data, the Dry Creek anticline appears to be a very different structure than other salt walls in the Paradox Basin. From a gentle salt pillow geometry across the Hamilton Creek field in the southeast, the structure changes dramatically to a spectacular pinched-off salt wall exposed at the surface to the northwest. 2D seismic profiles trending NE-SW across the Uncompahgre Front and into the Paradox Basin near the Hamilton Creek structure image thrust imbricates of the Uncompahgre Front (Late Proterozoic) overthrusting Pennsylvanian aged evaporites. A close study of the relationship between faulting and evaporite cycles within the Paradox Formation helps constrains the timing of movement of the Uncompahgre Front in southwestern Colorado. In addition, the Hamilton Creek/ Dry Creek anticline can be reconstructed back through time by tying the seismic data to field exposures of Mesozoic stratigraphic units flanking the Dry Creek anticline. These reconstructions constrain the timing of salt wall growth, the shortening associated with the Ancestral Rocky Mountain Uncompahgre Front, and later Laramide reactivation of preexisting structures. Interpretation of 3D seismic data calibrated to an extensive well dataset across the Hamilton Creek field will allow this producing field to be assessed for future petroleum development. A better understanding of the evolution of the salt-cored Dry Creek anticline will help assess the feasibility of future petroleum exploration along this structure, and aslo serve as an analog for shortened or pinched-off salt wall structures in other salt basins.