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A composite reference section for terminal Proterozoic strata of southern Namibia

Saylor, Beverly Z. and Kaufman, Alan J. and Grotzinger, John P. and Urban, Frank (1998) A composite reference section for terminal Proterozoic strata of southern Namibia. Journal of Sedimentary Research, 68 (6). pp. 1223-1235. ISSN 1527-1404.

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Integrated sequence stratigraphic and chemostratigraphic data yield a framework for correlations of stratigraphic units in the terminal Proterozoic to Cambrian Witvlei and Nama Groups of Namibia. Coupled with precise U-Pb zircon age constraints, these correlations make it possible to construct a composite reference section for use in calibrating terminal Proterozoic chronostratigraphy. The Namibian reference section starts with two distinct glacial horizons and extends up to within 1 million years of the Proterozoic-Cambrian boundary. The two glacial horizons may represent each of two distinct Varanger-age glaciations better known from the North Atlantic region. From the higher of the two glacial horizons up, the composite stratigraphy preserves one of the thickest and most complete available records of carbon-isotope variability in post-Varanger terminal Proterozoic seawater. Four carbon-isotope chemostratigraphic intervals are recognized: (1) a postglacial negative δ^(13)C excursion (Npg interval); (2) a rising interval (Pr interval) of increasing positive delta 13 C values; (3) a falling interval (Pf interval) characterized by decreasing positive δ^(13)C and culminating in near zero or negative values; and (4) an interval of moderately positive, relatively invariant δ^(13)C values (I interval) that extends up to the unconformity that contains the Proterozoic-Cambrian boundary. Each of these chemostratigraphic intervals can be recognized in widely separated correlative sections around the world. By comparing sediment accumulation rate in the radiometrically calibrated Namibian stratigraphy with sediment accumulation rates in correlative sections in Arctic Canada and Oman, a maximum age of 564 Ma is estimated for the end of the younger Varanger glaciation, 25 m.y. younger than previous estimates.

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Grotzinger, John P.0000-0001-9324-1257
Additional Information:© 1998 Society for Sedimentary Geology. Received 18 November 1996; accepted 24 May 1998. This research was supported by National Science Foundation grants EAR- 9205479 and EAR-9058199 to JPG and EAR 9510339 and EAR-9610339 to P. Hoffman and AJK. The Geological Survey of Namibia provided logistical support. National Science Foundation grant EAR 93-16238 to A. Knoll provided AJK the opportunity to visit Namibia. Charlie Hoffmann and members of the IGCP project 320 field trip to Namibia provided many ideas and stimulating conversation on the outcrop. Reviews by Nic Beukes, Peter Gresse, and an anonymous reviewer improved the manuscript and are greatly appreciated. Preparation of this manuscript was completed at the Department of Geology and Geophysics, University of Wisconsin at Madison.
Group:UNSPECIFIED, Division of Geological and Planetary Sciences
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NSFEAR 93-16238
Issue or Number:6
Record Number:CaltechAUTHORS:20130228-075442534
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Official Citation: Beverly Z. Saylor, Alan J. Kaufman, John P. Grotzinger, and Frank Urban A composite reference section for terminal Proterozoic strata of southern Namibia Journal of Sedimentary Research, November 1998, v. 68, p. 1223-1235, published online 1 November 1998, doi:10.2110/jsr.68.1223
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:37188
Deposited By: Ruth Sustaita
Deposited On:28 Feb 2013 17:29
Last Modified:03 Oct 2019 04:45

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