Precambrian-Cambrian transition problem in western North America: Part I. Tommotian fauna in the southwestern Great Basin and its implications for the base of the Cambrian System

An assemblage of shelly fossils has been discovered in the Lower Member of the Deep Spring Formation in Esmeralda County, Nevada. Preliminary taxonomic analysis suggests that the fossils consist of a variety of hyoliths, coleolids, and other elements. The fossils lie about 1,000 m down-section from the first trilobites and appear to be slightly younger than or possibly coeval with Wyattia. The fossils show affinities to Tommotian taxa from Siberia and other continents. Thus, partial stratigraphic equivalents to the Tommotian Stage, whose base marks the Precambrian-Cambrian boundary, can be defined for the southern Great Basin.