Permian and Triassic Namakiers in the Paradox Basin of Colorado and Utah, USA

Donald Rasmussen

Namakiers (salt glaciers) in the Paradox Basin first appeared after salt walls and diapirs formed during Desmoinesian through Wolfcampian and during and after a regional erosional event in the Leonardian. Only after the overburden of a diapir was breached at the surface was Pennsylvanian salt forced upward as a salt plug into the breach and then, by gravity collapse, away from the plug as a namakier. Namakiers are recognizable on seismic and well logs. Borehole samples contain stratum and rock fragments with distinct 'out-of-place' lithologies. Paradox Basin namakiers have a seismic signature similar to a Triassic namakier described in the German Permian Salt Basin, and dimensions and compositions similar to active namakiers in the Iranian Zagros Fold Belt. Multiple namakiers in SW Colorado at Gypsum Valley Diapir first flowed out upon the Leonardian unconformity and then were coeval with the deposition of the Leonardian Organ Rock redbeds on the flank of the diapir. Early Triassic namakiers in SE Utah are present on three diapirs where they flowed out upon the Triassic unconformity and then were coeval with and buried by Moenkopi redbeds. Preservation of the namakiers within fluvial redbeds in the Paradox Basin was likely due to an arid climate and rapid burial in the adjacent minibasins. Namakiers in the Paradox Basin may act as top seals for oil and gas accumulations on the flanks of the salt diapirs.

AAPG Search and Discovery Article #90156©2012 AAPG Rocky Mountain Section Meeting, Grand Junction, Colorado, 9-12 September 2012