Multiple Stages of Syndepositional Halokinetic (?) Deformation in the Permian Cutler Formation, Northern Margin of the Onion Creek Diapir, Paradox Basin, UT

Abstract

Permian Cutler Fm. fluvial and eolian strata are exposed on the northern side of the Onion Creek Diapir, Paradox Basin, UT and display a stacked series of 5 to 400 m-wavelength folds that trend subparallel to the diapir margin. Fault sets adjacent to the folds trend both radially from and subparallel to the diapir margin. Depositional facies mapping of the Permian Cutler Fm. dhows that both folding and faulting decrease in intensity within 200m from the diapir-sediment interface and ultimately vanish <4200 m from the exposed contact with the diapir. Fold wavelength, fault offset, and fault density change up section with stratigraphically younger units have longer wavelength folds with few to no faults. Onlap and angular unconformities between units filling in synclines and terminating on anticlines require syndepositional deformation to have occurred. Previous models rely on younger, tectonically controlled deformation. Abrupt and significant thickness changes among channelized conglomeratic sandstones between distal and near-diapir fold limbs also support this hypothesis. The centers of depositional thicks change between Cutler subunits. This correlates with a decrease in fold amplitude and wavelength from east to west along the diapir margin. The syndepositional deformation recorded in each fold suggests a folding of a thin sediment layer overlying a salt shoulder or salt wing. Salt shoulders are zones where the diapir margin steps abruptly inward recording narrowing of the diapir; whereas salt wings are outward expansions of the diapir margin that record depositional history over a shorter period of time. Both halokinetic features have been recognized elsewhere in the Paradox Basin. Geologic relationships are mapped and incorporated in a photogrammetric model to show the evolution of syndepositional folds along the diapir margin highlighting the relationship between accommodation space and passive diapiric movement. Changing depositional thicks observed among the Permian Cutler Fm. suggests that fluvial deposition onto an evolving diapir is influenced by the previously established distribution of accommodation space, in contrast with previous hypothesis. Understanding how fluvial systems interact with the margin of a salt diapir is critical in creating higher-resolution models of the distribution of potential reservoirs, seals, traps and migration pathways at the salt-sediment interface that would normally be of sub-seismic resolution.

AAPG Datapages/Search and Discovery Article #90350 © 2019 AAPG Annual Convention and Exhibition, San Antonio, Texas, May 19-22, 2019