Two or four Neoproterozoic glaciations?

Research Article| December 01, 1998 Two or four Neoproterozoic glaciations? Martin J. Kennedy; Martin J. Kennedy 1Department of Earth and Space Sciences and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90095-1567 Search for other works by this author on: GSW Google Scholar Bruce Runnegar; Bruce Runnegar 1Department of Earth and Space Sciences and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90095-1567 Search for other works by this author on: GSW Google Scholar Anthony R. Prave; Anthony R. Prave 2School of Geography and Geosciences, University of St. Andrews, Fife KY16 9ST, Scotland Search for other works by this author on: GSW Google Scholar K.-H. Hoffmann; K.-H. Hoffmann 3Geological Survey of Namibia, P.O. Box 2168, Windhoek, Namibia Search for other works by this author on: GSW Google Scholar Michael A. Arthur Michael A. Arthur 4Department of Geosciences and Earth System Science Center, Pennsylvania State University, University Park, Pennsylvania 16802 Search for other works by this author on: GSW Google Scholar Geology (1998) 26 (12): 1059–1063. https://doi.org/10.1130/0091-7613(1998)0262.3.CO;2 Article history first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Martin J. Kennedy, Bruce Runnegar, Anthony R. Prave, K.-H. Hoffmann, Michael A. Arthur; Two or four Neoproterozoic glaciations?. Geology 1998;; 26 (12): 1059–1063. doi: https://doi.org/10.1130/0091-7613(1998)0262.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract A thick Neoproterozoic carbonate and glaciogenic succession of the southern Congo craton has yielded δ13C and 87Sr/86Sr records through the later Cryogenian (ca. 750–600 Ma) and earlier part of the Terminal Proterozoic (ca. 600–570 Ma). Sizeable negative δ13C excursions (to less than–5‰) occur above each of two glacial intervals and the 87Sr/86Sr values of marine carbonates shift from ∼0.7072 to ∼0.7079 at the upper glacial level. These geochemical constraints provide a Marinoan (younger Varanger) age for the upper glacial interval, previously regarded as a second phase of the Sturtian glaciation. The δ13C record from the Congo craton is therefore incompatible with recent global δ13C syntheses that have identified four or more separate ice ages during the Neoproterozoic. A cladistic analysis of geologic and geochemical characters of 12 Neoproterozoic glacial deposits identifies two distinct groups that are found in a consistent stratigraphic order whenever two glacial units occur within a single succession. We use δ13C and 87Sr/86Sr records from the Congo craton and other key successions to test the null hypothesis that there were only two global glaciations (Sturtian and Marinoan) during the Neoproterozoic. Placing the GSSP (global stratotype section and point) for the base of the Terminal Proterozoic within or just above a cap carbonate of the younger (Marinoan) glaciogenic succession would confine all known Neoproterozoic glaciations to the Cryogenian. The rapid shift in marine 87Sr/86Sr to more radiogenic values during the Marinoan glaciation is opposite that predicted by the snowball Earth scenario which calls for continental runoff to cease during glaciation, resulting in a shift to less radiogenic values. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.