Stratigraphy and geochronology of the Tambien Group, Ethiopia: Evidence for globally synchronous carbon isotope change in the Neoproterozoic

摘要: The Neoproterozoic Era was an interval characterized by profound environmental and biological transitions. Existing age models for nonglacial intervals largely have been based on correlation of carbonate carbon isotope values, but there are few tests the assumed synchroneity these records between basins. In contrast to ash-poor successions typically targeted chemostratigraphy, Tonian Cryogenian Tambien Group (Tigray region, Ethiopia) deposited in arc-proximal basin where volcanic tuffs suitable U-Pb geochronology preserved within mixed carbonate-siliciclastic sedimentary succession. culminates a diamictite interpreted correlate ca. 717–662 Ma Sturtian snowball Earth glaciation. New physical stratigraphic data high-precision dates from intercalated lead new framework that confirms identification negative δ13C values Assem Formation limestones with 800 Bitter Springs stage. Integration Fifteenmile northwestern Canada constitutes positive test global Spring Stage constrains stage started after 811.51 ± 0.25 ended before 788.72 0.24 Ma. These temporal constraints strengthen case interpreting variation as record large-scale changes cycle provide paleogeographic change, geochemical cycling, evolution during radiation early eukaryotes.