Subglacial meltwater supported aerobic marine habitats during Snowball Earth.

Autor:	Lechte MA; School of Earth Sciences, University of Melbourne, Parkville, VIC 3010, Australia; maxwell.lechte@mail.mcgill.ca.; Department of Earth and Planetary Science, McGill University, Montréal, QC, Canada H3A 0E8., Wallace MW; School of Earth Sciences, University of Melbourne, Parkville, VIC 3010, Australia., Hood AVS; School of Earth Sciences, University of Melbourne, Parkville, VIC 3010, Australia., Li W; State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, 210093 Nanjing, China., Jiang G; Department of Geoscience, University of Nevada, Las Vegas, NV 89154., Halverson GP; Department of Earth and Planetary Science, McGill University, Montréal, QC, Canada H3A 0E8., Asael D; Department of Geology and Geophysics, Yale University, New Haven, CT 06511., McColl SL; School of Earth Sciences, University of Melbourne, Parkville, VIC 3010, Australia., Planavsky NJ; Department of Geology and Geophysics, Yale University, New Haven, CT 06511.
Jazyk:	angličtina
Zdroj:	Proceedings of the National Academy of Sciences of the United States of America [Proc Natl Acad Sci U S A] 2019 Dec 17; Vol. 116 (51), pp. 25478-25483. Date of Electronic Publication: 2019 Dec 02.
DOI:	10.1073/pnas.1909165116
Abstrakt:	The Earth's most severe ice ages interrupted a crucial interval in eukaryotic evolution with widespread ice coverage during the Cryogenian Period (720 to 635 Ma). Aerobic eukaryotes must have survived the "Snowball Earth" glaciations, requiring the persistence of oxygenated marine habitats, yet evidence for these environments is lacking. We examine iron formations within globally distributed Cryogenian glacial successions to reconstruct the redox state of the synglacial oceans. Iron isotope ratios and cerium anomalies from a range of glaciomarine environments reveal pervasive anoxia in the ice-covered oceans but increasing oxidation with proximity to the ice shelf grounding line. We propose that the outwash of subglacial meltwater supplied oxygen to the synglacial oceans, creating glaciomarine oxygen oases. The confluence of oxygen-rich meltwater and iron-rich seawater may have provided sufficient energy to sustain chemosynthetic communities. These processes could have supplied the requisite oxygen and organic carbon source for the survival of early animals and other eukaryotic heterotrophs through these extreme glaciations. Competing Interests: The authors declare no competing interest.
Databáze:	MEDLINE
Externí odkaz:	Zobrazit plný text záznamu