Journal article

Enigmatic chambered structures in Cryogenian reefs: The oldest sponge-grade organisms?

Malcolm W Wallace, Ashleigh VS Hood, Estee MS Woon, Karl-Heinz Hoffmann, Christopher P Reed



Previously undescribed chambered structures are common and widespread in the Cryogenian (post-Sturtian glacial) carbonates of the Oodnaminta Reef Complex (Adelaide Geosyncline, South Australia), the Rasthof-Berg Aukas Formation (Namibia) and the Gauss Formation (Namibia). These carbonate structures have millimetre to centimetre-scale chambers separated by well-defined and generally thin micritic walls. Chamber walls now consist of dolomite, but were probably originally aragonitic. The chambers may have a lobate, polygonal or dendritic morphology and are often further divided into smaller chambers. Chambered structures occur as reefal growth frameworks; as cavity-fillings in neptunean dykes a..

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Awarded by ARC

Funding Acknowledgements

We are most grateful to Marg and Doug Sprigg of Arkaroola Wilderness Sanctuary for their generous support of fieldwork over many years. We appreciate the help given by Gammon Ranges National Park staff for access to the Oodnaminta Reef. We also thank Sabre Resources (Matt Painter and Eddie van Dyke), Teck Namibia (particularly Andrea Reed and Eckhart Fryer) and Weatherly International PLC (Mike Stuart) for logistic support and access to drill core during fieldwork in Namibia. This research is partially funded from ARC Discovery Grant DP130102240. We would also like to thank three anonymous reviewers, whose many helpful suggestions improved the manuscript.