Cited by 256Paleontology and Stratigraphy of FossilsGeological and Geochemical AnalysisGeology and Paleoclimatology Research

A composite reference section for terminal Proterozoic strata of southern Namibia

Saylor, Beverly Z., Kaufman, Alan J., Grotzinger, John P., Urban, Frank·1998·Journal of Sedimentary Research

Abstract

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 delta 13C excursion (Npg interval); (2) a rising interval (Pr interval) of increasing positive delta 13C values; (3) a falling interval (Pf interval) characterized by decreasing positive delta 13C and culminating in near zero or negative values; and (4) an interval of moderately positive, relatively invariant delta 13C 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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Crossref · 10.2110/jsr.68.1223

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Authors
Saylor, B. Z., Kaufman, A. J., Grotzinger, J. P., & Urban, F.
Affiliations
Massachusetts Institute of Technology (US)
Venue
Journal of Sedimentary Research
Published
1998-11-01
Volume
68
Issue
6
Pages
1223-1235
ISSN
  • 0022-4472 (ISSN-L)
  • 1938-3681
  • 1527-1404
OpenAlex
W2126802403
Cited by
256
References
35
Citations by year
2026: 7 · 2025: 4 · 2024: 9 · 2023: 8 · 2022: 3 · 2021: 9 · 2020: 9 · 2019: 6 · 2018: 13 · 2017: 7 · 2016: 8 · 2015: 7 · 2014: 5 · 2013: 6 · 2012: 4
FWCI
12.46
Type
journal article
Language
en
Open access
closed
Locations
  • Journal of Sedimentary Research (publishedVersion)
  • PubMed (publishedVersion)
  • CaltechAUTHORS (California Institute of Technology) (submittedVersion)
Topics
  • Physical Sciences › Earth and Planetary Sciences › Paleontology › Paleontology and Stratigraphy of Fossils
  • Physical Sciences › Earth and Planetary Sciences › Geophysics › Geological and Geochemical Analysis
  • Physical Sciences › Earth and Planetary Sciences › Atmospheric Science › Geology and Paleoclimatology Research
Keywords
Nama Group, carbon isotope stratigraphy, zircon U-Pb geochronology, chronostratigraphy, sediment accumulation rates, Namibia, Oman, Canadian Arctic
MeSH terms
Carbon Isotopes, Carbonates, Cold Climate, Fossils, Geology, Ice, Namibia, Seawater, Geologic Sediments, Evolution, Planetary, Geological Phenomena

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