Paleoproterozoic Snowball Earth: Extreme Climatic and Geochemical Global Change and Its Biological Consequences

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 97; no. 4; pp. 1400 - 1405
• Main Authors: Kirschvink, Joseph L., Gaidos, Eric J., Bertani, L. Elizabeth, Beukes, Nicholas J., Gutzmer, Jens, Maepa, Linda N., Steinberger, Rachel E.
• Format: Journal Article
• Language: English
• Published: Legacy CDMS National Academy of Sciences of the United States of America 15.02.2000; National Acad Sciences; National Academy of Sciences; The National Academy of Sciences
• Subjects: Africa; Bacteria; Carbonates; Climate; Cyanobacteria; Earth, Planet; Enzymes; Evolution; Evolution, Molecular; Geochemistry; Geology; Glacial landforms; Ice; Iron; Manganese; Meteorology And Climatology; Molecular Sequence Data; Oceans; Oceans and Seas; Oxidation; Oxygen; Phylogeny; Physical Sciences; Precipitation; Prehistoric era; Snowball Earth hypothesis; Superoxide Dismutase; Time; Africa
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.97.4.1400

Geological, geophysical, and geochemical data support a theory that Earth experienced several intervals of intense, global glaciation ("snowball Earth" conditions) during Precambrian time. This snowball model predicts that postglacial, greenhouse-induced warming would lead to the deposition of banded iron formations and cap carbonates. Although global glaciation would have drastically curtailed biological productivity, melting of the oceanic ice would also have induced a cyanobacterial bloom, leading to an oxygen spike in the euphotic zone and to the oxidative precipitation of iron and manganese. A Paleoproterozoic snowball Earth at 2.4 Giga-annum before present (Ga) immediately precedes the Kalahari Manganese Field in Southern Africa, suggesting that this rapid and massive change in global climate was responsible for its deposition. As large quantities of O2are needed to precipitate this Mn, photosystem II and oxygen radical protection mechanisms must have evolved before 2.4 Ga. This geochemical event may have triggered a compensatory evolutionary branching in the Fe/Mn superoxide dismutase enzyme, providing a Paleoproterozoic calibration point for studies of molecular evolution.