Mid-Neoproterozoic (~830-750 Ma) isotope stratigraphy of Australia and global correlation

A. C. Hill, M. R. Walter*

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    75 Citations (Scopus)

    Abstract

    Carbon and strontium isotope studies of numerous drillcore and outcrop sections within individual Australian Neoproterozoic basins, in a tectonic and sedimentologic framework, have allowed the construction of isotopic records for the interval 830-750 Ma. This, combined with the discovery of a restricted stratigraphic range for the acritarch Cerebrosphaera buickii in mid-Neoproterozoic strata of Australia, makes possible correlation with successions in Canada, Namibia and Spitsbergen. That part of the mid-Neoproterozoic succession in Spitsbergen which contains C. buickii was previously considered younger than the Sturtian glacial epoch, but this study has indicated that the Akademikerbreen Group is older than that. A correlation scheme is proposed along five tie lines, and is based on a correlation between Australia and Canada at ~830 Ma, and Australia, Spitsbergen and Namibia at ~760 Ma. The lowest ever recorded seawater 87Sr/86Sr ratios in the upper Shaler Supergroup of Canada (0.70561-0.70670) compare with ratios in evaporites of the ~830 Ma Bitter Springs Formation, Amadeus Basin, Australia (0.70568-0.70720). Comparable δ13C(carb) records support a correlation. At about 760 Ma, a correlation is made between the heaviest mid-Neoproterozoic δ13C(carb) values of 7.2‰ (upper Burra Group, Adelaide Rift Complex) and 8.1‰ (Kanpa Formation, western Officer Basin) in Australia, 8.5‰ in Spitsbergen (Backlundtoppen Formation, Akademikerbreen Group), and 8.5‰ in Namibia (Ombombo Subgroup, Congo Craton). The stratigraphic range of C. buickii in Australia and Spitsbergen supports this correlation. A compilation of δ13C(carb) and 87Sr/86Sr records between about 830 and 750 Ma from Australia, Canada, Namibia and Spitsbergen reveals numerous negative excursions, which are not associated with preserved glacial deposits. It is necessary, therefore, to consider additional models to the 'Snowball Earth' to explain the large and rapid carbon isotopic excursions. (C) 2000 Elsevier Science B.V. All rights reserved.

    Original languageEnglish
    Pages (from-to)181-211
    Number of pages31
    JournalPrecambrian Research
    Volume100
    Issue number1-3
    DOIs
    Publication statusPublished - Mar 2000

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