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Correlation and naming |
1 Geological Survey of Western Australia, 100 Plain Street, East Perth, Western Australia 6004, Australia; Research Associate, School of Earth and Planetary Sciences, Macquarie University, New South Wales, 2109, Australia; Honorary Research Associate, School of Geosciences, Monash University,Melbourne, Victoria, 3800, Australia (e-mail: kath.grey{at}doir.wa.gov.au)
2 Mineral Resources Tasmania, PO Box 56, Rosny Park, Tasmania 7018, Australia
Now that a Global Stratotype Section and Point (GSSP) has been ratified and a new system defined for the terminal Proterozoic era, the Ediacaran, the next step is to develop global correlations and to further subdivide this system. Means of correlating and subdividing older parts of the Proterozoic era are also needed. This is not a simple task. Phanerozoic correlations depend on biostratigraphic zonation made possible by biodiversity, supported by geochronology. Proterozoic biotas are more restricted, geochronological data is often sparse, and although rapid and significant carbon isotope excursions are present through some time intervals, the curve is essentially quiescent and of limited utility at other times. Nevertheless, a foundation for Ediacaran acritarch biostratigraphy has now been established in Australia and linked to the carbon-isotope curve using sample splits. In conjunction with other correlation techniques, this has allowed the development of a continent-wide correlation scheme. The Australian Ediacaran experience suggests that an integrated approach offers the best way forward for Proterozoic subdivision. However, it raises issues about some aspects of Neoproterozoic correlation; in particular, it indicates that reliance on a two-main-glaciations model may be over simplistic.
