Age of the Western Iron Ore Group, India, and implications for pre-GOE oxygenation of oceans at the twilight of Archean-Proterozoic transition.

Increasing concentrations of oxygen in the early atmosphere contributed to the development of the Earth's ozone shield and thus ushered in the growth of photoautotrophs. The proliferation of multicellular life is linked with the rise of atmospheric oxygen, known as the Great Oxidation Event (GOE). However, it has become evident that the permanent trend of rising oxygen in the atmosphere was preceded by multiple fluctuations. It is imperative to gather information from immediate pre- and post-GOE successions for constraining this transformation. The greenstone successions from > 3.8 Ga to the Archean-Proterozoic transition are important candidates for deciphering the evolution of the atmosphere and hydrosphere. The Archean Singhbhum craton, eastern India, hosts a well-preserved low-grade greenstone succession, the Western Iron Ore Group (W-IOG), containing banded iron formations (BIF) from pre-GOE stratigraphy. We report here zircon U-Pb LA-ICPMS age of ~ 2500 Ma from felsic tuff below the BIF and detrital zircon age of ~ 2730 Ma from underlying sandstones that constrain the age of the younger cycle of BIF deposition in the W-IOG as Neoarchean grading into the Paleoproterozoic. The newly reported Neoarchean to Paleoproterozoic age of the W-IOG provides potential opportunity for future research on the tempos and events immediately ahead of the GOE in the oceanic realm at the Archean-Proterozoic boundary.