Evidence for two pulses of glaciation during the late Proterozoic in northern Utah and southeastern Idaho

Recent mapping of Fremont Island in Great Salt Lake, the Wasatch Range between Ogden and Brigham City, and the Sheeprock Mountains shows that glacial episodes represented either by diamictite or by dropstones enclosed in fine-grained laminated beds are separated by as much as 1,000 m of non-glacial deposits. Using reasonable sedimentation rates for such deposits, we infer that two episodes of glaciation, each probably consisting of multiple advances and retreats, were separated by a non-glacial interval of a few hundred thousand to a few million years' duration. Only the younger of the two episodes recorded in the allochthon is represented by the diamictites of the autochthon.--Modified journal abstract.