In research published online in Nature Geoscience, Ian Campbell and Charlotte Allen of the Australian National University in Canberra propose that when tectonic forces caused the creation of supercontinents such as Pangaea and Gondwana, massive mountain chains were formed. These, they believe, then rapidly eroded, releasing vast amounts of nutrient-rich sediments into the oceans, which stimulated the growth of oxygen-producing phytoplankton and bacteria.

Campbell and Allen reached their conclusions by dating zircon crystals found in the ancient beds of river deltas – including that of the Ganges (left) – which they believe formed following the continental collisions. Their analysis identified five separate collision events that, they discovered, coincided with sharp increases in atmospheric oxygen levels identified by previous studies.

‘Our study was initiated to date the timing of formation of the continental crust,’ said Campbell. ‘We had not expected to see a correlation between supercontinent formation and the recognised step increases in atmospheric oxygen.’

October 2008