3D SEISMIC REFLECTION DATA CONSTRAINTS ON STRUCTURAL AND TECTONIC EVOLUTION OF THE NORTHWESTERN PARADOX BASIN, SOUTHEASTERN UTAH

The Paradox Basin lies within the Colorado Plateau province and is defined by the presence and distinctive influence of the interbedded sequence of evaporites and clastics that comprise the Pennsylvanian Paradox Formation. Due to excellent outcrop exposure and energy and mineral resources within the basin, it has been the subject of extensive prior study; however, many aspects of its tectonic evolution remain contentious due to limited availability of subsurface data constraints. A recently acquired 3D seismic reflection dataset near Green River, Utah permits new observations and interpretations of subsurface geology that provide valuable insight into the tectonic basin evolution. Based on interpretation of these data through mapping of horizons and faults, creation of sediment thickness (isopach) maps, observations of stratigraphic features from geophysical attributes, and comparison with structural models, we document details about the subsurface geology of this region in unprecedented detail and compare with previous regional interpretations. The deepest portion of the seismic volume illuminates features in the basement interpreted as an intrusive sill complex and a set of predominantly strike-slip faults that cut the basement through the Mississippian section that were active during limited intervals of the Cambrian and early Pennsylvanian. Above that section, complex thin-skinned contractional faults and folds within the Pennsylvanian Paradox Formation accommodate shortening in the core of the Green River anticline. Detailed observations within this interval demonstrate the influence of the basement fault geometry on shortening, the role of salt-clastic interval thicknesses on structural style, and the role of key salt intervals as internal detachments. Maps of sediment thickness and channel systems in overlying Permian through Early Cretaceous sedimentary sections reveal local stratigraphic patterns related to regional depositional settings and constrain the timing of the growth of the Green River anticline as predominantly post-Jurassic. Finally, the subsurface extent of the Little Grand Wash fault is also captured in these data, defining it as a listric normal fault detached within the lower Paradox Formation with growth intervals in the late Pennsylvanian and post-Jurassic.