Re-Os Isotopic age Constraints on Deposition in the Neoproterozoic Amadeus Basin: Implications for the "Snowball Earth"

Re-Os isotopes have been measured on organic-rich sediments from the Neoproterozoic Aralka Formation in the Amadeus Basin, central Australia. These sediments closely predate the Marinoan glaciation, a correlative of the global "Snowball II" event. The Aralka formation sediments preserve an isochronous relationship defining an age of 592 +/- 14 Ma, which is interpreted to represent the age of deposition. This age is substantially younger than that inferred from global correlation studies. It indicates that the onset, duration and cessation of the glacial event, and subsequent deposition of >2km of sediment prior to radiation of the earliest metazoan life assemblages is confined to ca. 40 Myr. Our findings imply that the Terminal Proterozoic glaciations were of rapid onset and short duration.