South Australian U-Pb zircon (CA-ID-TIMS) age supports globally synchronous Sturtian deglaciation

Abstract

A central prediction of the Snowball Earth hypothesis is that glacial onset should be synchronous at low latitudes, and its termination should be rapid and synchronous globally. High precision U/Pb zircon ages provide supporting evidence for the synchronous onset (within error) of the Sturtian glaciation (ca. 716 Ma) on multiple continents. Successful application of Re-Os techniques on organic rich shales and carbonates allow for the possibility of a globally synchronous Sturtian deglaciation (ca. 660 Ma), but the sparse isotopic age constraints leave this open to debate. Here we report the first high precision U-Pb zircon age of 663.03  0.11 Ma (2) for the end Sturtian recorded in the Bolla Bollana Formation of South Australia. This age supports previously published ages and is permissive with a globally synchronous deglaciation. In conjunction with the timing of glacial onset, this age reinforces the ca. 58 Myr duration of the Sturtian Snowball.

Hit or miss: Glacial incisions of snowball Earth

“…Given a ~58‐Ma‐long Sturtian glaciation (Cox et al., ; Rooney et al., ), how much glacial erosion might we expect? Depending predominantly on latitude and altitude, glacial erosion rates for the Quaternary ice ages vary across several orders of magnitude (Delmas, Calvet, & Gunnell, ; Hallet, Hunter, & Bogen, ).…”

“…650–635 Ma “Marinoan”, defining Cryogenian time (Bao et al., ; Macdonald et al., ; Rooney, Strauss, Brandon, & Macdonald, ; Shields‐Zhou, Porter, & Halverson, ). The glacial‐periglacial origin of Cryogenian diamictites is widely accepted and the snowball Earth hypothesis has gained favour since globally synchronous glacial terminations are increasingly supported radiometrically (Cox et al., ; Rooney et al., ). The longer of the two Cryogenian glaciations, the ~58‐Ma‐long Sturtian glaciation (Cox et al., ; Rooney et al., ), thus represents one of the longest‐known glaciations in Earth history.…”

Dating the late Proterozoic stratigraphic record

“…In the absence of direct radiometric ages, easily identified GTS boundaries, or biostratigraphic zonation (e.g. [63,76]), other approaches are required to tell time in this and many other sedimentary successions of this time interval.…”

Major shoreline retreat and sediment starvation following Snowball Earth

“…These “Snowball Earth” events represent some of the most remarkable intervals in the geological record (Harland, ; Hoffman, Kaufman, Halverson, & Schrag, ; Kirschvink, ). Although recent progress has been made calibrating Cryogenian geochronology (Cox et al, ; Rooney et al, ), many aspects surrounding the timing and duration of Snowball Earth events remain enigmatic. A central tenet of the hypothesis is that sea‐level rise during and following deglaciation could have been as rapid as ~2,000 years (ka), i.e., about five times faster than Holocene glacioeustatic sea‐level rise (Hoffman et al, ; Hyde, Crowley, Baum, & Peltier, ).…”