Sequence stratigraphy and biostratigraphy of the lower member of the Deep Spring Formation: Implications for the Neoproterozoic-Cambrian boundary in the Basin and Range Province, western United States
The Deep Spring Formation of the southern Basin and Range Province provides information valuable in locating and correlating the Precambrian-Cambrian boundary in western North America. Sequence-stratigraphic analysis of the lower Deep Spring Formation revealed three sequence boundaries. The proposed sequence-stratigraphic model includes early highstand slumps, a feature interpreted to be unique to mixed systems, which form at the onset of the Highstand Systems Tract; This study identified the small shelly fossil Cloudina in the lower Deep Spring Formation. Cloudina was previously unrecognized at this stratigraphic level in the Basin and Range. This Neoproterozoic fossil is associated in the lower Deep Spring Formation with the shelly fossils Nevadatubulus and Sinotubulites, which traditionally are believed to be Cambrian in age. Based on the revisions to the biostratigraphy from this and other studies, the lower member is interpreted as Neoproterozoic in age and not Cambrian, as previously reported.