Great oxidation event

The rate of H2 escape from the upper atmosphere and thus oxygenation from decomposition of H2O vapour is directly dependent on the density of H2 at the critical level of escape. It may be that the Great Oxidation Event from 2.4 Ga to 2.0 Ga reflects elevated H2 in the hydrosphere / atmosphere during much of this period. 

Holland H. D. (2002) Volcanic gases, black smokers, and the great oxidation event. Geochim. Cosmochim. Acta 66, 3811-3826. 

In contrast, Ohmoto (1996, 1997) and Beukes et al. (2002) argue that the Great Oxidation Event interpretation does not take into account the reducing power of biological activity within Precambrian paleosols, and that O2 levels were close to present levels from 3,000 Ma to 1,800 Ma. An intermediate view of rising, but fluctuating atmospheric oxidation also is compatible with available paleosol data (Retallack, 2001a), and with limited evidence from mass-independent fractionation of sulfur isotopes (Farquhar et al., 2002). 

Yang W. and Holland H. D. (2003) The Hekpoort paleosol at Strata 1 Gaborone, Botswana soil formation during the Great Oxidation Event. Am. J. Sci. 303, pp. 187-220. 

One consequence of the proposed great oxidation event (GOE) of the atmosphere between 2.3 Ga and 2.0 Ga is that trace elements such as molybdenum, rhenium, and uranium, which are mobile during weathering in an oxidized environment, would have been essentially immobile before 2.3 Ga. Their concentration in seawater would then have been very much lower than today, and their enrichment in organic carbon-richshales would have been minimal. This agrees with the currently available data (Bekker et al., 2002 Yang and Holland, 2002). Carbonaceous shales older than ca. 2.3 Ga are not enriched in molybdenum, rhenium, and uranium. A transition... 

FIGURE 5.12 The probable evolution of atmospheric oxygen over time given the constraints discussed in the text. The solid curve is inferred from sulfur isotope MIF, the dotted curve is taken mostly from Canfield (2005). GOE is the great oxidation event of Holland (2002). Qv. Catling and Claire (2005). 

On this basis Holland (2003) proposed that prior to the "Great Oxidation Event" at 2.3 Ga (see Section 5.3.1.6) the abundances of these elements should be low in organic shales, whereas after 2.3 Ga, when the oceans were more oxidizing their concentrations should be much higher. This was investigated by Siebert... 

Schirrmeister BE, de Vos JM, AntoneUi A, Bagheri HC Evolution of multicellularity coincided with increased diversification of cyanobacteria and the Great Oxidation Event, Proc... 

Dutkiewicz, A., Volk, H., George, S.C., Ridley, I, Buick, R. (2006) Biomarkers from Huronian oil-bearing fluid inclusions an uncontaminated record of life before the Great Oxidation Event. Geology, 34,437 40. 

FIG. 6.5 The nickel famine and a possible chemical explanation. Top The loss of nickel from ocean water predated the Great Oxidation Event 2.5 billion years ago. Bottom Melting points decrease across the second half of the transition metals, which may explain why nickel sohdified and entered the mantle, while copper and zinc remained at the surface. 

The time when oxygen increased is such an important event that it has been named several times over. Most scientists call it the Great Oxidation Event or the Great Oxygenation Event, but some call it the Oxygen Catastrophe. ... 

The step up in oxygen was followed by a swift step down in temperature, an event called Snowball Earth in which ice covered most of the Earth. The mechanism is not entirely worked out, but each Great Oxidation Event was accompanied by a Great Freezing, and each time, the planet came disturbingly close to becoming a lifeless chunk of icy rock. Oxygen turned Eden into Hoth. 

In the seas, banded iron formations once again painted the bottom with iron and oxygen, like in the original Great Oxidation Event, creating the second BIF peak in Figure 8.1 in Chapter 8. At least three or four cold snaps passed over the planet like an inverse fever. The chemistry of the oceans changed dramatically, and soon after, so did life. 

After the Second Great Oxidation Event had done most of its work, the planet reached a stable threshold of oxygen levels, near today s, with oxygen present from the air to the deep sea. While surface ocean oxygen increased 10 times, deep ocean oxygen increased a million times. A hundred million years later, after the events of the Great Unconformity, the Cambrian Explosion exploded. Ifwe scale the history of life... 

First, burrowing appears to have stabilized the planet s chemistry. It connected the oxygen and phosphorous cycles so that feedbacks between them would stabilize each and dampen the magnitude of later booms and busts. As a result, later events like the supposed third Great Oxidation Event were relatively less drastic. 

Anoxia A state of very low or absent oxygen. The Earth was anoxic before the Great Oxidation Event 2.5 billion years ago. 

Banded iron formations (BIFs) Oxygen-iron rock layers formed from reduced plus-two iron ions reacting with oxygen, coinciding with the two Great Oxidation Events. 

Great Oxidation Event (GOE) A worldwide change 2.5 billion years ago, when the atmosphere gained steady and detectable levels of oxygen from photosynthesizing microbes. A lesser event occurred about 700 million years ago, sometimes called the second GOE. 

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