CANCELLED - SEMINAR: CMCA Seminar Series: Atmospheric anoxia: an Archean absolute (or even absolutely Archean)?

Unfortunately this event has been cancelled.

This week's seminar by Dr Boswell Wing has now been cancelled due to unforeseen events.

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Dr Boswell Wing from Earth and Planetary Sciences, McGill University will introduce the S MIF proxy for pO2 and describe the gross constraints that it provides on atmospheric anoxia through Earth history. Canonical wisdom holds that Earth’s history of atmospheric oxygen is essentially binary. The secular evolution of oxygen partial pressure (pO2) is inferred from records of reduced detrital minerals, oxidized paleosols, banded iron formation, and more recently, mass-independent fractionation (MIF) of sulfur isotopes; all point to a significant increase in pO2 at &#8776;2.4 Ga. The most quantitative constraint on this timeline comes with the loss of S MIF, which requires pO2 <10-5 present atmospheric levels for its production and preservation. To date, it has been widely assumed that this threshold was never crossed in the Archean and that Archean-like levels of atmospheric O2 never returned after the Paleoproterozoic ‘great oxidation event’. Dr Boswell Wing will present a pair of case studies – one from mid-Archean strata associated with voluminous volcanic eruptions and one from ca. 635 Ma rocks associated with a low-latitude glaciation – that call into question a simple binary interpretation of atmospheric anoxia.