Spherules and shard-like clasts from the late Proterozoic Acraman impact ejecta horizon, South Australia

— Spherules and irregular shard-like particles consisting of authigenic mineral phases have been identified in the Acraman impact ejecta horizon preserved within the late Proterozoic shales of the Adelaide Geosyncline, South Australia. The spherules (150 μm to 1 mm diameter) range in shape from near-spherical through ellipsoidal to extended ellipsoidal-dumbbell. The distinctive morphology of the spherules and shard-like particles and their restriction to the ejecta horizon, suggest that they were deposited initially as glassy bodies which subsequently have been pseudomorphed by more stable authigenic phases like calcite, quartz, albite, and barite.