Editors

Paul F. Hoffman

Document Type

Article

Publication Date

12-17-2019

Publication Title

Proceedings of the National Academy of Sciences of the United States of America

Volume

116

Issue

51

First page number:

25478

Last page number:

25483

Abstract

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.

Keywords

Oxygenation; Glaciation; Snowball Earth; Iron formation; Fe isotopes

Disciplines

Earth Sciences | Physical Sciences and Mathematics

File Format

pdf

File Size

1.230 KB

Language

English

Available for download on Wednesday, June 17, 2020

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