The quest for an Australian Cambrian stage scale

Abstract

The chronostratigraphical scale is a hierarchical scheme that is subdivided into increasingly smaller units, from eonothem down to the level of the substage and beyond. Boundaries of chronostratigraphic intervals typically coincide with individual bioevents. As these intervals become smaller, their geographic utility tends to shrink. Typically, where the original interval is inapplicable, the next highest interval in the scale is used for communication. Where appropriate intervals are unavailable, confusion reigns. A stadial subdivision of the Australian mid–late Cambrian (equivalent to the international Miaolingian and Furongian series) was completed in 1993 with the definition of the Furongian Iverian Stage. One stage, the Ordian, was initially suggested as the lowest stage for what is now the Miaolingian, but should be considered to belong to upper Series 2 of the Cambrian. No older Cambrian stages have been proposed in Australia. Indeed, the base of the Ordian has not been defined, due in part to the incompleteness of Series 2 successions in central and northern Australia. A longstanding impediment to the establishment of lower Cambrian stages in Australia arises from the fact that the entire Australian stadial scheme for the Miaolingian and Furongian series was established in the cratonic basins of central-northern Australia, whereas the lower Cambrian is best developed in separate South Australian basins. With the rapid increase in knowledge of the biostratigraphic successions in the South Australian lower Cambrian (Terreneuvian and Series 2) over the last three decades, the time seems ripe for the establishment of such a stadial subdivision. This will require careful correlation between the mostly Terreneuvian and Series 2 succession in South Australia and the mostly Miaolingian–Furongian succession in central and northern Australia. Taxa that can be used for such a stadial subdivision include trilobites, organophosphatic brachiopods, archaeocyaths, small shelly fossils, molluscs and acritarchs, as each has provided the basis of zonations in the South Australian successions.

John R. Laurie [[email protected]], Geoscience Australia, Symonston Australian Capital Territory 2601, Australia, and School of Natural Sciences, Macquarie University, North Ryde, New South Wales 2109, Australia. Peter D. Kruse [[email protected]], South Australian Museum, Adelaide South Australia 5000, Australia. Glen A. Brock [[email protected]], School of Natural Sciences, Macquarie University, North Ryde, New South Wales 2109, Australia. James D. Holmes [[email protected]], Palaeoscience Research Centre, University of New England, Armidale New South Wales 2351, Australia. James B. Jago [[email protected]], University of South Australia-STEM, Mawson Lakes, SA 5095, Australia, and South Australian Museum, Adelaide, South Australia 5000, Australia. Marissa J. Betts [[email protected]], Palaeoscience Research Centre/LLUNE, University of New England, Armidale New South Wales 2351, Australia. John R. Paterson [[email protected]], Palaeoscience Research Centre, University of New England, Armidale New South Wales 2351, Australia. Patrick M. Smith [[email protected]], Australian Museum Research Institute, Sydney New South Wales 2010, Australia, and School of Natural Sciences, Macquarie University, North Ryde New South Wales 2109, Australia.

Keywords:

• Cambrian
• stages
• Australia

Acknowledgements

The authors thank the Adnyamathanha People, generous homestead owners and leaseholders, and the National Parks and Wildlife Service South Australia for permission to sample lower Cambrian successions across the Flinders Ranges over the past 30 years. JRL thanks his colleagues at Geoscience Australia; Natalie Schroeder and Steven Petkovski, for their assistance and support. GAB would also like to personally thank the late Tom Bradley, David Mathieson and a bevy of Honours and postgraduate students and volunteers from Macquarie University for assistance in the field and for collecting, processing and providing large portions of the biostratigraphic, chemostratigraphic and lithostratigraphic data from the numerous lower Cambrian sections in the Arrowie and Stansbury basins that are discussed here as potential regional stage boundaries. Similarly, MJB and JRP would like to thank all students and volunteers at the University of New England for their contributions to these datasets. PMS thanks Peter Jell, Ian Percival and Yong Yi Zhen for providing access to material from New South Wales for study. The authors thank the staff of the South Australian Drill Core Reference Library, Northern Territory Geological Survey Core Library and Geoscience Australia for access to relevant Cambrian drill holes. JBJ thanks the University of South Australia for logistic support. Funding has been provided by various Australian Research Council (ARC) grants (especially Discovery Project #120104251 to GAB and JRP). The authors also thank Dr S. Jacquet (Geological Sciences, University of Missouri) and an anonymous reviewer for improving the manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).