Re–Os isotopes have been measured on organic-rich sedimentary rocks from the Neoproterozoic Aralka Formation in the Amadeus Basin, central Australia. These sedimentary rocks closely predate the Marinoan glaciation, a correlative of the global ‘Snowball II’ event. The Aralka Formation sedimentary rocks preserve 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 >2 km of sediment prior to radiation of the earliest metazoan life assemblages is confined to c.40 million years.