Upper Oligocene evaporites in basin fill of Sevier Desert region, western Utah

The basin fill beneath the Sevier Desert of western Utah contains evaporites that were deposited in a broad closed basin. All of the basin fill penetrated by the Gulf Oil 1 Gronning contains abundant volcanic detritus and its alteration products of Cenozoic age. Fission-track dating of tuffaceous sandstone yields ages of 26-28 m.y. Fossil pollen from mudstone in the evaporite-bearing strata includes forms no older than late Oligocene, in good agreement with the fission-track ages. Thus the age of evaporites is late Oligocene and younger. Anhydrite is present throughout approximately 900m of volcaniclastic rocks in the lower part of the section cut by the Gulf hole. Fossil pollen are indicative of an arid to semiarid flora.-from Authors