Paradigm shift in determining Neoproterozoic atmospheric oxygen
Nigel J.F. Blamey 1,2,3, Uwe Brand 1, John Parnell 3, Natalie Spear 4, Christophe Lécuyer 5, Kathleen Benison 6, Fanwei Meng 7 and Pei Ni 8
- Author Affiliations
1Department of Earth Sciences, Brock University, 1812 Sir Isaac Brock Way, St Catharines, Ontario L2S 3A1, Canada
2Department of Earth and Environmental Science, New Mexico Tech, 801 Leroy Place, Socorro, New Mexico 87801, USA
3Department of Geology and Petroleum Geology, University of Aberdeen, AB24 3Ue Aberdeen, Scotland
4Department of Earth and Environmental Science, University of Pennsylvania, Philadelphia, Pennsylvania 19014, USA
5Laboratoire de Géologie de Lyon, UMR CNRS 5276, University of Lyon and Institut Universitaire de France, 69622 Villeurbanne, France
6Department of Geology and Geography, University West Virginia, Morgantown, West Virginia 26506, USA
7Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, #39 East Beijing Road, Nanjing 210008, China
8School of Earth Sciences and Engineering, Nanjing University, Nanjing 210093, China
Source/Fonte: Frontiers in Earth Science
Abstract
We present a new and innovative way of determining the oxygen level of Earth's past atmosphere by directly measuring inclusion gases trapped in halite. After intensive screening using multiple depositional, textural/fabric, and geochemical parameters, we determined that tectonically undisturbed cumulate, chevron, and cornet halite inclusions may retain atmospheric gas during crystallization from shallow saline, lagoonal, and/or saltpan brine. These are the first measurements of inclusion gas for the Neoproterozoic obtained from 815 ± 15–m.y.–old Browne Formation chevron halite of the Officer Basin, southwest Australia. The 31 gas measurements afford us a direct glimpse of the composition of the mid- to late Neoproterozoic atmosphere and register an average oxygen content of 10.9%. The measured pO2 puts oxygenation of Earth's paleoatmosphere ∼100–200 m.y. ahead of current models and proxy studies. It also puts oxygenation of the Neoproterozoic atmosphere in agreement with time of diversification of eukaryotes and in advance of the emergence of marine animal life.
Received 28 March 2016. Revision received 7 June 2016. Accepted 9 June 2016.
©The Authors
Gold Open Access: This paper is published under the terms of the CC-BY license.
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