Norian (Upper Triassic) sediments in western Nevada were deposited in a west-facing successor basin which was formed following the collision of the microcontinent Sonomia in the Late Paleozoic. These strata were deposited on a shelf and in a deep basin and consist of siliciclastic sandy and pelitic strata with interbedded carbonate strata.

Conodonts of the genus Epigondolella are common in the basinal strata but are rarely found in carbonates deposited on the shelf. This suggests that Epigondolella may have been facies selective. The trace fossils, Cruziana, Planolites, Skolithos, and Cylindrichnus, are present in sandstone deposited on...