Using chemostratigraphy to correlate and calibrate unconformities in neoproterozoic strata from the southern Great Basin of the United States

An integrative approach combining carbon-isotope stratigraphy, biostratigra phy, and sequence stratigraphy was used to correlate between and place tent ative age constraints on previously undated Neoproterozoic-Cambrian units o f the Death Valley and White-Inyo successions, southern Great Basin. United States. Two regionally correlatable disconformities have been identified i n the poorly fossiliferous, pre-trilobite strata. By comparing the carbon-i sotope tl ends in the succession to a hypothetical global reference curve, the temporal magnitude of each hiatus can be postulated. The younger hiatus approaches 30 m.y. in duration and separates strata (Hines Tongue/basal St irling unconformity) between 580 Ma and 550 Ma. The older hiatus represents similar to 10 m.y. and separates strata (Wyman-Reed and upper Johnnie unco nformity) between similar to 590 and 580 Ma. The unconformities may he rela ted to global sea-level fluctuations in response to Neoproterozoic ("Snowba ll Earth") glacial events or tectonic activity as predicted by thermal subs idence models, and as such, may provide critical data to evaluate these glo bal phenomena.