Nature and significance of the Neoproterozoic Sturtian–Marinoan Boundary, Northern Adelaide Geosyncline, South Australia

Abstract

Abstract The Cryogenian succession of the Northern Flinders Ranges reveals a complex sedimentary record between the Sturtian and Marinoan glacial deposits. A major unconformity separates the Sturtian and Marinoan-aged sedimentary successions in the area. This forms a subaerial erosion surface with terrestrial and marginal marine infill directly above the Angepena and Balcanoona Formations in their respective localities. This exposure surface is here correlated with the previously documented submarine unconformity between the Yankaninna Formation and the underlying deep marine Tapley Hill Formation. This erosional event provides a chronostratigraphic marker horizon that coincides approximately with thepreviously defined Sturtian–Marinoan Time Series boundary in the Northern Flinders Ranges. These stratigraphic relationships also constrain lateral facies relationships between the Oodnaminta ReefComplex (Balcanoona Formation) and the Angepena Formation. Similarly, the shallow-water Weetootla Dolomite is correlated with the deeper water carbonates of the Yankaninna Formation. Key words: CryogenianSturtianMarinoanUmberatana GroupstratigraphyBalcanoona FormationAngepena Formationunconformity Acknowledgements We thank Doug and Margaret Sprigg of Arkaroola Wilderness Sanctuary, and also the Gammon Ranges National Park rangers for support in regard to carrying out fieldwork in the Northern Flinders Ranges. We also thank reviews from Vic Gostin and one anonymous reviewer for their careful and constructive comments that improved the final manuscript.