Journal
EARTH AND PLANETARY SCIENCE LETTERS
Volume 466, Issue -, Pages 12-19Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.epsl.2017.02.046
Keywords
ocean oxygenation; carbonate geochemistry; Devonian; plant evolution; rare earth elements; cerium anomaly
Categories
Funding
- ARC [DP130102240]
- NAI Postdoctoral Fellowship
- NSF-ELT program
- Alternative Earths NASA Astrobiology Institute
Ask authors/readers for more resources
There has been extensive debate about the history of Earth's oxygenation and the role that land plant evolution played in shaping Earth's ocean-atmosphere system. Here we use the rare earth element patterns in marine carbonates to monitor the structure of the marine redox landscape through the rise and diversification of animals and early land plants. In particular, we use the relative abundance of cerium (Ce-anom), the only redox-sensitive rare earth element, in well-preserved marine cements and other marine precipitates to track seawater oxygen levels. Our results indicate that there was only a moderate increase in oceanic oxygenation during the Ediacaran (average Cryogenian Ce-anom = 1.1, average Ediacaran Ce-anom = 0.62), followed by a decrease in oxygen levels during the early Cambrian (average Cryogenian Ce-anom = 0.90), with significant ocean anoxia persisting through the early and mid Paleozoic (average Early Cambrian-Early Devonian Ce-anom = 0.84). It was not until the Late Devonian that oxygenation levels are comparable to the modern (average of all post-middle Devonian Ce-anom = 0.55). Therefore, this work confirms growing evidence that the oxygenation of the Earth was neither unidirectional nor a simple two-stage process. Further, we provide evidence that it was not until the Late Devonian, when large land plants and forests first evolved, that oxygen levels reached those comparable to the modern world. This is recorded with the first modern-like negative Ceanom (values <0.6) occurring at around 380 Ma (Frasnian). This suggests that land plants, rather than animals, are the 'engineers' responsible for the modern fully oxygenated Earth system. (C) 2017 Elsevier B.V. All rights reserved.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available