title: Carbon isotope evidence for the stepwise oxidation of the Proterozoic environment
abstract: The oxidation of the Earth's crust and the increase in atmospheric oxygen early in Earth history have been linked to the accumulation of reduced carbon in sedimentary rocks.  Trends in the carbon isotope composition of sedimentary organic carbon and carbonate show that during the Proterozoic aeon (2.5-0.54 Gyr ago) the organic carbon reservoir grew in size, relative to the carbonate reservoir.  This increase, and the concomitant release of oxidizing power in the environment, occurred mostly during episodes of global rifting and orogeny.
authors.affiliation: NASA, Ames Research Center, Moffett Field, California 94035.
authors.forename: D J
authors.initials: DJ
authors.lastname: Des Marais
authors.forename: H
authors.initials: H
authors.lastname: Strauss
authors.forename: R E
authors.initials: RE
authors.lastname: Summons
authors.forename: J M
authors.initials: JM
authors.lastname: Hayes
mesh_terms: D001272:Atmosphere; D005075:Biological Evolution; D002244:Carbon / Q000032:analysis / Q000737:chemistry*; D002247:Carbon Isotopes; D002254:Carbonates / Q000032:analysis; D018534:Earth, Planet; D055593:Geological Phenomena; D005844:Geology; D000069497:Origin of Life; D010084:Oxidation-Reduction; D010100:Oxygen / Q000032:analysis*; D010163:Paleontology
chemical_list: D002247:Carbon Isotopes; D002254:Carbonates; D002244:Carbon; D010100:Oxygen