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Neoproterozoic variations in the C-isotopic composition of seawater: stratigraphic and biogeochemical implicationsThe recent proliferation of stratigraphic studies of delta 13C variation in carbonates and organic C in later Neoproterozoic and basal Cambrian successions (approximately 850-530 Ma) indicates a strong oscillating trend in the C-isotopic composition of surface seawater. Alone, this trend does not adequately characterize discrete intervals in Neoproterozoic time. However, integrated with the vectorial signals provided by fossils and Sr-isotopic variations, C isotope chemostratigraphy facilitates the interbasinal correlation of later Neoproterozoic successions. Results of these studies are evaluated in terms of four stratigraphic intervals: (1) the Precambrian/Cambrian boundary, (2) the post-Varanger terminal Proterozoic, (3) the late Cryogenian, and (4) the early Cryogenian. Where biostratigraphic or radiometric data constrain the age of Neoproterozoic sedimentary sequences, secular variations in C and Sr isotopes can provide a level of stratigraphic resolution exceeding that provided by fossils alone. Isotopic data place strong constraints on the chemical evolution of seawater, linking it to major tectonic and paleoclimatic events. They also provide a biogeochemical framework for the understanding of the initial radiation of macroscopic metazoans, which is associated stratigraphically, and perhaps causally, with a global increase in the burial of organic C and a concomitant rise of atmospheric O2.
Document ID
20040089677
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Kaufman, A. J.
(Botanical Museum, Harvard University Cambridge, MA 02138, United States)
Knoll, A. H.
Date Acquired
August 21, 2013
Publication Date
January 1, 1995
Publication Information
Publication: Precambrian research
Volume: 73
ISSN: 0301-9268
Subject Category
Geosciences (General)
Funding Number(s)
CONTRACT_GRANT: BSR90-17747
Distribution Limits
Public
Copyright
Other
Keywords
NASA Discipline Exobiology
Non-NASA Center

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