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Published August 9, 2005 | Published + Supplemental Material
Journal Article Open

The paleoproterozoic snowball Earth: A climate disaster triggered by the evolution of oxygenic photosynthesis


Although biomarker, trace element, and isotopic evidence have been used to claim that oxygenic photosynthesis evolved by 2.8 giga-annum before present (Ga) and perhaps as early as 3.7 Ga, a skeptical examination raises considerable doubt about the presence of oxygen producers at these times. Geological features suggestive of oxygen, such as red beds, lateritic paleosols, and the return of sedimentary sulfate deposits after a approximate to 900-million year hiatus, occur shortly before the approximate to 2.3-2.2 Ga Makganyene "snowball Earth" (global glaciation). The massive deposition of Mn, which has a high redox potential, practically requires the presence of environmental oxygen after the snowball. New age constraints from the Transvaal Supergroup of South Africa suggest that all three glaciations in the Huronian Supergroup of Canada predate the Snowball event. A simple cyanobacterial growth model incorporating the range of C, Fe, and P fluxes expected during a partial glaciation in an anoxic world with high-Fe oceans indicates that oxygenic photosynthesis could have destroyed a methane greenhouse and triggered a snowball event on timescales as short as 1 million years. As the geological evidence requiring oxygen does not appear during the Pongola glaciation at 2.9 Ga or during the Huronian glaciations, we argue that oxygenic cyanobacteria evolved and radiated shortly before the Makganyene snowball.

Additional Information

© 2005 by the National Academy of Sciences. Communicated by Paul F. Hoffman, Harvard University, Cambridge, MA, June 14, 2005 (received for review April 8, 2004). Published online before print August 1, 2005, 10.1073/pnas.0504878102 We thank R. Adler, N. Beukes, R. Blankenship, J. Brocks, H. Dorland, A. Kappler, J. Kasting, A. Maloof, D. Newman, S. Ono, A. Sessions, D. Sumner, T. Raub, B. Weiss, and three anonymous reviewers for advice and discussion; R. Tada for help with fieldwork in the Huronian; A. Pretorius and Assmang Limited for access to Nchwaning Mine; and P. Hoffman for communicating this manuscript. This work was supported in part by the Agouron Institute and by a National Aeronautics and Space Administration Astrobiology Institute cooperative agreement with the University of Washington. R.E.K. was supported by a National Science Foundation Graduate Research Fellowship and a Moore Foundation Fellowship. Author contributions: R.E.K. and J.L.K. designed research; R.E.K., I.A.H., and C.Z.N. performed research; R.E.K., J.L.K., and I.A.H. analyzed data; and R.E.K. and J.L.K. wrote the paper.

Attached Files

Published - KOPpnas05.pdf

Supplemental Material - KOPpnas05supfig2.pdf

Supplemental Material - KOPpnas05suptext.pdf


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