The quest for an Australian Cambrian stage scale

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 [john.r.laurie@gmail.com], 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 [archaeo.kruse@gmail.com], South Australian Museum, Adelaide South Australia 5000, Australia. Glen A. Brock [glenn.brock@mq.edu.au], School of Natural Sciences, Macquarie University, North Ryde, New South Wales 2109, Australia. James D. Holmes [jamesholmes83@gmail.com], Palaeoscience Research Centre, University of New England, Armidale New South Wales 2351, Australia. James B. Jago [Jim.Jago@unisa.edu.au], University of South Australia-STEM, Mawson Lakes, SA 5095, Australia, and South Australian Museum, Adelaide, South Australia 5000, Australia. Marissa J. Betts [Marissa.Betts@une.edu.au], Palaeoscience Research Centre/LLUNE, University of New England, Armidale New South Wales 2351, Australia. John R. Paterson [jpater20@une.edu.au], Palaeoscience Research Centre, University of New England, Armidale New South Wales 2351, Australia. Patrick M. Smith [Patrick.Smith@austmus.gov.au], Australian Museum Research Institute, Sydney New South Wales 2010, Australia, and School of Natural Sciences, Macquarie University, North Ryde New South Wales 2109, Australia.