TEMPO AND MODE OF NEOPROTEROZOIC GLACIATIONS: AN UPDATE

Existing U-Pb and Re-Os geochronological constraints from several paleocontinents indicate an exceptionally long-duration (57 Myr) for the Sturtian glaciation and a shorter-lived (>4 Myr) Marinoan glaciation. Despite incremental refinements to the Cryogenian chronology, the tempo and mode of Neoproterozoic glaciation has remained uncertain and controversial. This is due in part to differing interpretations of the sedimentology of these deposits, uncertainty in the chronostratigraphy of Cryogenian successions globally, futher compounded by a lack of a critique that assesses the variable quality of the existing geochronological database. Here we present new U-Pb (zircon) CA-ID-TIMS dates from air fall tuffs combined with Re-Os dates on sedimentary rocks from Cryogenian succession from South China. We then follow the example set by the paleomagnetic community in providing quality assessments for geochronological data and assign grades to existing geochronological constraints on Neoproterozoic glacial deposits. These new data, when integrated with radio-isotopic data from other globally distributed Cryogenian successions develops the temporal framework within which, we can start to quantify the tempo of Cryogenian glaciations. This framework supports a globally synchronous termination to both the Sturtian and Marinoan glaciation. Multiple dates within sections now permits transformation of depth/thickness information into the time domain allowing an improved understanding of what the Cryogenian stratigraphic record represents. By building on the success of the U-Pb EARTHTIME initiative we outline a pathway to increase precision, standardize data reduction methods and expand the application of the sedimentary Re-Os geochronometer to the geological rock record.