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Chuar Group of the Grand Canyon: record of breakup of Rodinia, associated change in the global carbon cycle, and ecosystem expansion by 740 MaThe Chuar Group (approximately 1600 m thick) preserves a record of extensional tectonism, ocean-chemistry fluctuations, and biological diversification during the late Neoproterozoic Era. An ash layer from the top of the section has a U-Pb zircon age of 742 +/- 6 Ma. The Chuar Group was deposited at low latitudes during extension on the north-trending Butte fault system and is inferred to record rifting during the breakup of Rodinia. Shallow-marine deposition is documented by tide- and wave-generated sedimentary structures, facies associations, and fossils. C isotopes in organic carbon show large stratigraphic variations, apparently recording incipient stages of the marked C isotopic fluctuations that characterize later Neoproterozoic time. Upper Chuar rocks preserve a rich biota that includes not only cyanobacteria and algae, but also heterotrophic protists that document increased food web complexity in Neoproterozoic ecosystems. The Chuar Group thus provides a well-dated, high-resolution record of early events in the sequence of linked tectonic, biogeochemical, environmental, and biological changes that collectively ushered in the Phanerozoic Eon.
Document ID
20040088829
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Karlstrom, K. E.
(University of New Mexico Albuquerque 87131, United States)
Bowring, S. A.
Dehler, C. M.
Knoll, A. H.
Porter, S. M.
Des Marais, D. J.
Weil, A. B.
Sharp, Z. D.
Geissman, J. W.
Elrick, M. B.
Timmons, J. M.
Crossey, L. J.
Davidek, K. L.
Date Acquired
August 21, 2013
Publication Date
July 1, 2000
Publication Information
Publication: Geology
Volume: 28
Issue: 7
ISSN: 0091-7613
Subject Category
Geosciences (General)
Funding Number(s)
CONTRACT_GRANT: EAR-9706541
Distribution Limits
Public
Copyright
Other
Keywords
NASA Discipline Exobiology
NASA Center ARC

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