DISCOVERY OF AN EXPOSED EARLY TRIASSIC NAMAKIER (SALT GLACIER) ON THE WEST FLANK OF THE ONION CREEK DIAPIR IN GRAND COUNTY, UTAH

Namakiers (salt glaciers) in the subsurface on the flanks of salt diapirs in the Paradox Basin of SE Utah and SW Colorado are recognized in seismic data and in well logs, borehole samples and cores (Rasmussen, 2014). Distinct “out-of-the-ordinary” stratum and rock fragments within local surface exposures on the flanks of some diapirs, with respect to strata of their host Triassic stratigraphic formations, have been interpreted as namakier debris from extruded salt and associated strata. Multiple namakiers first flowed out upon the Early Permian Leonardian unconformity and were coeval with the deposition of the Organ Rock Formation redbeds on the northeast flank of the Gypsum Valley Diapir; subsurface data indicate other extrusive domes and namakiers may have existed at the same time on the Paradox Valley, Castle Valley and Salt Valley diapirs. Triassic namakiers first flowed out upon the Early Triassic unconformity and were coeval with Moenkopi Formation redbeds during the Induan, Olenekian and Anisian. Moenkopi namakiers are in the subsurface on the Pine Ridge, Moab Valley and Salt Valley diapirs; outcrop data suggest extrusive domes and namakiers may have existed at the same time on the Castle Valley, Onion Creek, Sinbad Valley and Paradox Valley diapirs. Reinterpretation of Permian and Triassic outcrops on the west flank of the Onion Creek Diapir in May 2016 resulted in the discovery of remnants of an Early Triassic namakier that flowed west at least 3020 feet (920 m) across folded and eroded Permian Organ Rock strata prior to being buried by Moenkopi fluvial strata. The proximal namakier debris contains chaotic large rock fragments, blocks of extruded strata, gypsum-cemented strata and gypsum. The distal namakier debris contains strata after halite dissolution, gypsum, gypsum-rich mudstone, and rock fragments, with the namakier strata/debris distorted during flowage and by salt dissolution. This is likely the only namakier exposed in the Rocky Mountain region.