Stratigraphy and sequence stratigraphy of the Neoproterozoic (Cryogenian–Ediacaran) Stuart Shelf, South Australia

Abstract

The Stuart Shelf is part of the Adelaide Superbasin overlying the Gawler Craton and Cariewerloo Basin in South Australia. The basin is of interest for sediment-hosted copper mineralisation known to be hosted in numerous stratigraphic intervals across the region. Therefore, facies analysis and understanding of spatial distribution of host units are essential for exploration targeting and mineral systems research. Our study presents improved and new definitions of Cryogenian and Ediacaran Stuart Shelf stratigraphy, and a detailed, regional-scale sequence stratigraphic analysis. The Cryogenian non-glacial interlude was of particular interest, as it includes the Tapley Hill Formation, a known host for copper mineralisation. The succession of Tapley Hill Formation (including Sturtian cap carbonates), Brighton Limestone and Angepena Formation represents a third-order depositional cycle, an equivalent to the lowermost cycle of the Cryogenian non-glacial interlude in the adjacent Adelaide Rift Complex. The Ediacaran post-glacial succession includes the Nuccaleena Formation and Tent Hill Formation and is interpreted as a second-order depositional cycle. The Sturtian and Marinoan cap carbonates form regional stratigraphic marker horizons and were deposited in a transgressive systems tract. Variations in facies and thickness can be linked to development of localised depocentres and topographic highs, such as the Pernatty High. Modelling of 3D surfaces reveals a shift in the basin orientation between the Cryogenian and Ediacaran sedimentation from an NNW–SSE axis towards a N–S axis. The Stuart Shelf sequence stratigraphic framework provides new insights in the basin sedimentology and evolution, which aids sediment-hosted mineral systems analysis and improves the understanding of Cryogenian and Ediacaran basin evolution in Australia.