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Carbon isotopic composition of individual Precambrian microfossilsIon microprobe measurements of carbon isotope ratios were made in 30 specimens representing six fossil genera of microorganisms petrified in stromatolitic chert from the approximately 850 Ma Bitter Springs Formation, Australia, and the approximately 2100 Ma Gunflint Formation, Canada. The delta 13C(PDB) values from individual microfossils of the Bitter Springs Formation ranged from -21.3 +/- 1.7% to -31.9 +/- 1.2% and the delta 13C(PDB) values from microfossils of the Gunflint Formation ranged from -32.4 +/- 0.7% to -45.4 +/- 1.2%. With the exception of two highly 13C-depleted Gunflint microfossils, the results generally yield values consistent with carbon fixation via either the Calvin cycle or the acetyl-CoA pathway. However, the isotopic results are not consistent with the degree of fractionation expected from either the 3-hydroxypropionate cycle or the reductive tricarboxylic acid cycle, suggesting that the microfossils studied did not use either of these pathways for carbon fixation. The morphologies of the microfossils suggest an affinity to the cyanobacteria, and our carbon isotopic data are consistent with this assignment.
Document ID
20040088830
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
House, C. H.
(University of California Los Angeles 90095-1567, United States)
Schopf, J. W.
McKeegan, K. D.
Coath, C. D.
Harrison, T. M.
Stetter, K. O.
Date Acquired
August 21, 2013
Publication Date
August 1, 2000
Publication Information
Publication: Geology
Volume: 28
Issue: 8
ISSN: 0091-7613
Subject Category
Geosciences (General)
Distribution Limits
Public
Copyright
Other
Keywords
Non-NASA Center
NASA Discipline Exobiology

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