Figure 1

Suggested chronology of geological, atmospheric, and biological events during the Hadean, Archean, and Paleoproterozoic eons. Geological events were compiled from references within Canup and Righter (2000), Eriksson et al. (2004), and Van Kranendonk et al. (2007a, 2007b). Asteroidal impact history is by Glikson (2007). Emplacement of the oceans is by Nutman (2006). The dashed line at 2,500 Ma marks an abrupt change into an oxygenated atmosphere (see Kendall et al. 2010), although oxygen may have started accumulating beforehand (Ohmoto 2004). Oxygenation events are considered to have occurred in pulses of unknown magnitude and duration and are correlated with a putative origin of oxygenic photosynthesis by cyanobacteria, based on a theoretical timing estimated by Lazcano and Miller (1994) and considering the emergence of life at 3,800 Ma. On the line of cyanobacteria, alternative origins are indicated with a black (Schirrmeister et al. 2013) or a white mark (Kirschvink and Kopp 2008). The MISS (Microbially Induced Sedimentary Structures; see Noffke et al. 2001), cyanobacteria, and the unicellular eukaryotic-like acritarchs are represented within both aquatic and terrestrial realms. Glaciations are from Hoffman and Schrag (2002), shown in combined colors to represent atmospheric (climatic) and hydrological (ice formation) processes. Other biological evolutionary steps and paleosol-related data are from Hallbauer and van Warmelo (1974), Holland (1984), Schopf (1983), Schopf and Klein (1992), Han and Runnegar (1992), Golubic and Seong-Joo (1999), Rye and Holland (2000), Retallack (2001), Westall et al. (2006a, 2006b), Johnson et al. (2009,2010), El Albani et al. (2010), Javaux et al. (2010), and Noffke (2010).