Publication Date:
2022-05-25
Description:
Author Posting. © Royal Society, 2006. This is the author's version of the work. It is posted here by permission of Royal Society for personal use, not for redistribution. The definitive version was published in Philosophical Transactions of the Royal Society B: Biological Sciences 361 (2006): 931-950, doi:10.1098/rstb.2006.1840.
Description:
Earth’s biogeochemical cycle of carbon delivers both limestones and organic materials to the crust.
In numerous, biologically catalyzed redox reactions, hydrogen, sulfur, iron, and oxygen serve
prominently as electron donors and acceptors. The progress of these reactions can be reconstructed from
records of variations in the abundance of 13C in sedimentary carbonate minerals and organic materials.
Because the crust is always receiving new CO2 from the mantle and a portion of it is being reduced by
photoautotrophs, the carbon cycle has continuously released oxidizing power. Most of it is represented
by Fe3+ that has accumulated in the crust or been returned to the mantle via subduction. Less than 3% of
the estimated, integrated production of oxidizing power since 3.8 Ga is represented by O2 in the
atmosphere and dissolved in seawater. The balance is represented by sulfate. The accumulation of
oxidizing power can be estimated from budgets summarizing inputs of mantle carbon and rates of
organic-carbon burial, but levels of O2 are only weakly and indirectly coupled to those phenomena and
thus to carbon-isotopic records. Elevated abundances of 13C in carbonate minerals ~2.3 Gyr old, in
particular, are here interpreted as indicating the importance of methanogenic bacteria in sediments rather
than increased burial of organic carbon.
Description:
JMH receives support as a member of the Astrobiology team led
by S. D’Hondt, University of Rhode Island. JRW is supported by an NDSEG Graduate Fellowship from
the Office of Naval Research.
Keywords:
Carbon cycle
;
Carbon isotopes
;
Atmospheric oxygen
;
Methanogenesis
;
Subduction
;
Mantle
Repository Name:
Woods Hole Open Access Server
Type:
Preprint
Format:
452171 bytes
Format:
application/pdf
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