CONTINENTAL GROWTH, OROGENY AND THE GREAT OXIDATION EVENT HELP COMPLEX LIFE on EARTH

The tectonic records of Neoarchean to early Paleoproterozoic (2.8 to 2.3 Ga) terranes indicates a link between evolving global tectonics with the formation of stable continents, increased subaerial volcanism and increased orogenic mountain building and the rise of atmospheric oxygen on Earth ~2.4 billion years ago. The Neoarchean record started at ~2.8Ga involving the breakup of a single pre-existing continent and the most prodigious period of generation and preservation of juvenile continental crust in Earth history during a period of mantle plume breakout (`2.72 to 2.65 Ga). During this period of high sea levels many cratons formed and aggregated into larger cratons or continents. Lower sea levels between 2.65 and 2.55 Ga were followed by a second (~2.51 to 2.45 Ga) period of plume breakout. This resulted in a global peak in magmatism and was associated with evidence for orogenic belts (mountain belts) in cratons in South Australia, Antarctica, India, China and North America between 2.5 and 2.3 Ga. Continued aggregation of continental fragments during this period may have resulted in the Earth’s first supercontinent and a return to low sea levels and relative tectonic quiescence. Although oxygenic photosynthetic bacteria are thought to have evolved by 2.71 Ga or 2.5 Ga the irreversible rise of atmospheric oxygen appears to have occurred between 2.45 and 2.32 Ga following the second plume breakout suggesting a dynamic linkage between tectonics and both the sources and sinks of oxygen. This suggests that both an increase in the oxidation state of volcanic gasses during the second plume breakout (due to increased subaerial volcanism) coupled with an increase in the weathering of continental crust due to the formation mountain belts (reducing carbon dioxide) helped a rise in atmospheric oxygen leading to the Great Oxidation Event a key event to help Earth’s complex life evolve.