ANOXIA-MEM · Probing the Memory of Earth Anoxia: New Stable Isotope Constraints on the Rise of Oxygen
Horizon 2020 — Marie Skłodowska-Curie Actions
- Duration
- 2016-04-01 → 2018-03-31
- EU contribution
- €185,076
- Participants
- 1
- Scheme
- MSCA-IF
Lines connect the coordinator with its partners.
Results in brief
Probing the Memory of Earth Anoxia: New Stable Isotope Constraints on the Rise of Oxygen
"The evolution of the Earth surface environment is marked by the Great Oxidation Event (GOE), circa 2.5 to 2.3 billion years ago, when atmospheric oxygen concentrations increased above 0.001% with key evidence for this found in sulfur isotopes in the rock record. Anomalous sulfur isotope signals that can only be explained by extremely low oxygen levels before 2.5 billion years ago and disappear thereafter. However, these sulfur isotope signals slowly disappear over more than 100 million years of time and this feature has been described by a possible ""memory effect"", as described by Reinhard et al. (2013), where weathering of older anomalous sulfur in rocks is redeposited in newly formed rocks. The result of this scenario is that a signal of no atmospheric oxygen, with respect to anomalous sulfur isotopes, may be indicated in the rock record even though there is oxygen present in the atmosphere. A test of this ""memory effect"" would strengthen our understanding of the history of Earths' atmospheric oxygen and therefore its relationship to the evolution of life on Earth, with which it is inextricably linked, and may help us understand the potential for atmospheric oxygen on other planets in our solar system and beyond. Sulfate is an excellent archive of sulfur and oxygen isotope signals in the rock record due to its widespread occurrence and strong preservation and suitable sulfate from around the time of the GOE can be used to test for the presence of the weathering ""memory effect"". Direct evidence for the ""memory effect"" would show up in sulfate records with significant sulfur isotope anomalies that run in parallel to coexisting sulfide records, and sulfate oxygen isotope compositions that indicate the origin of the sulfate from oxidative weathering of older sedimentary sulfides on the continental surface. Such sulfate was recovered in the form of trace barium sulfate (barite) from drill cores from the Turee Creek Group sedimentary sequence from western Australia, circa 2.45 to 2.21 billion years old, in the critical time window of the GOE."
Data: CORDIS, © European Union
Project objective
Atmospheric anoxia prevailed throughout the majority of Earth history, making oxygen and the animal life it supports relative newcomers to our planet. O2 accumulated in Earth’s atmosphere during two dramatic oxygenation events at ~2400 and ~600 million years ago (Ma). Both of these events were accompanied by profound biological and geochemical revolution, including the origin of animal life, making them amongst the most important events the Earth system has ever witnessed. Because the composition of Earth’s ancient atmosphere cannot be measured directly, its history must be examined using models constrained by geochemical proxies. The disappearance of sulfur isotope mass-independent fractionation (S-MIF) from the sedimentary record ca. 2320 Ma is considered the “smoking gun” evidence for the permanent oxygenation of Earth’s atmosphere. However, it was recently suggested that weathering of older S-MIF bearing sediments resulted in a prolonged S-MIF “memory effect” that lasted ~200 Ma or more, thus obscuring the true history of atmospheric oxygenation. Here I propose new hypotheses to test, for the first time, the importance of the S-MIF memory effect at the onset of atmospheric oxygenation. I will evaluate specific sulfur, strontium, and oxygen isotope signals from exciting new samples obtained through a recent French drilling program to help resolve this fundamental problem in Earth system evolution. As an American Experienced Researcher, this Marie Curie project, ANOXIA-MEM, is designed to harmonize my unique isotope geochemistry skills with the knowledge, resources, and training capacity of two renowned French isotope laboratories for the maximum benefit of all parties. This project promises new tools and analyses that are uniquely poised to upset the prevailing paradigm for Earth’s atmospheric oxygenation.
Original text from CORDIS.
Participants
- UNIVERSITE DE BREST · BRESTCoordinatorFrance
Links
Data: CORDIS, © European Union