Timeball Hill

The presence of O2 in the atmosphere-ocean system at 2.32 Ga is supported strongly by the presence of a large body of shallow-water hema-titic ironstone ore in the Timeball Hill Formation, South Africa (Beukes et al., 2002a,b). Apparently, the shallow oceans have been oxidized ever since. The deeper oceans may have continued in a reduced state at least until the disappearance of the Paleoproterozoic BIFs ca. 1.7 Ga. 

Beukes N. J., Dorland H., and Gutzmer J. (2002a) Pisolitic ironstone and ferricrete in the 2.22-2.4 Ga Timeball Hill Formation, Transvaal Supergroup implications for the... 

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