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The post-Paleozoic chronology and mechanism of 13C depletion in primary marine organic matterCarbon-isotopic compositions of geoporphyrins have been measured from marine sediments of Mesozoic and Cenozoic age in order to elucidate the timing and extent of depletion of 13C in marine primary producers. These results indicate that the difference in isotopic composition of coeval marine carbonates and marine primary photosynthate was approximately 5 to 7 permil greater during the Mesozoic and early Cenozoic than at present. In contrast to the isotopic record of marine primary producers, isotopic compositions of terrestrial organic materials have remained approximately constant for this same interval of time. This difference in the isotopic records of marine and terrestrial organic matter is considered in terms of the mechanisms controlling the isotopic fractionation associated with photosynthetic fixation of carbon. We show that the decreased isotopic fractionation between marine carbonates and organic matter from the Early to mid-Cenozoic may record variations in the abundance of atmospheric CO2.
Document ID
20040089581
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Popp, B. N.
(Indiana University Bloomington 47405-5101, United States)
Takigiku, R.
Hayes, J. M.
Louda, J. W.
Baker, E. W.
Date Acquired
August 21, 2013
Publication Date
April 1, 1989
Publication Information
Publication: American journal of science
Volume: 289
ISSN: 0002-9599
Subject Category
Exobiology
Funding Number(s)
CONTRACT_GRANT: NGR15003-118
CONTRACT_GRANT: PCM 84-04996
Distribution Limits
Public
Copyright
Other
Keywords
Non-NASA Center
NASA Program Exobiology
NASA Discipline Exobiology
NASA Discipline Number 52-30

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