Zircon age evidence for the Late Precambrian Acraman ejecta blanket

Abstract

The U‐Pb ages of zircons from a tuff‐like layer in the Late Precambrian Bunyeroo Formation in the central and southern Flinders Ranges, South Australia, show that the layer was not formed from volcanic detritus contemporaneous with sedimentation. The ages, dominantly 1575 ± 11 Ma, are consistent with the layer having been derived largely from the Gawler Range Volcanics. On this and other evidence, the layer has been identified as the ejecta blanket from a large bolide impact (Gostin et al 1986). Zircons from a second tuff‐like layer in the Bunyeroo Formation from the northern Flinders Ranges are dominantly much younger, 1143 ± 26 Ma, and have been abraded by sedimentary processes, indicating that that layer is not part of the same blanket.