title: Carbon isotopic studies of organic matter in precambrian rocks.
abstract: Reduced carbon in early Precambrian cherts of the Fig Tree and upper and middle Onverwacht groups of South Africa is isotopically similar (the average value of delta(13)C(PDB) is -28.7 per mil) to photosynthetically produced organic matter of younger geological age. Reduced carbon in lower Onverwacht cherts (Theespruit formation) is anomalously heavy (the average value of delta(13)C(PDB) is -16.5 per mil). This discontinuity may reflect a major event in biological evolution.
authors.forename: D Z
authors.initials: DZ
authors.lastname: Oehler
authors.forename: J W
authors.initials: JW
authors.lastname: Schopf
authors.forename: K A
authors.initials: KA
authors.lastname: Kvenvolden