COMPARING HETEROGENEITIES IN SYN-DEPOSITIONAL STYLES OF DEFORMATION WITHIN THE CUTLER GROUP, ONION CREEK DIAPIR SALT SHOULDER, PARADOX BASIN, UT: INSIGHTS INTO THE INTERACTIONS BETWEEN SALT DIAPIRISM, DEFORMATION AND DEPOSITION

The outcropping Northern side Onion Creek Salt Diapir, Paradox Basin, Utah, is a 5 km long by .5 km wide salt shoulder which represents an abrupt instep of the margin of the diapir. Permian Cutler Group fluvial and eolian strata unconformably overlie the salt shoulder and exhibit variable styles of faulting, and folding between exposures in 4 modern canyons that trend roughly perpendicular to the diapir margin. We differentiate the Cutler Group into 30 mappable stratigraphic subunits laying between the Onion Creek Salt Diapir contact and the Triassic Moenkopi basal unconformity in the cliffs to the north. Through integrating stratigraphic sections, high resolution field mapping using a gps-enabled tablet and a 3D photogrammetric outcrop model the complex history of Permian diapirism, deposition and syndepositional deformation is visualized and structurally restored. Field observations of facies-dependent paleocurrent directions show a history of coarser Cutler strata progressively onlapping onto the diapir with finer grained facies recording flow directions parallel to the diapir. Deformation extends up to 500m away from the exposed diapir in a zone with variable folding and radial faulting. Radial faults with normal offset extend from the diapir and variably offset different Permian Cutler Fm. Broader folds are found farther from the salt-sediment contact. Growth strata in these more open synclines create “thicks” in syncline axes and “thins” on anticline limbs within specific units, recording the timing of syndepostional deformation. Kink-folds nearer to the diapir are tighter, and some contain reverse faults in the cores of shale intervals in the folds. We present an integrated interpretation where Cutler Group fluvial sediments were deposited on the instep of a rising diapir margin. As the diapir rose, gravity sliding from the inboard margin of the diapir induced folding and faulting that was recorded by syndepositional deformation.