期刊
SCIENCE
卷 346, 期 6209, 页码 635-638出版社
AMER ASSOC ADVANCEMENT SCIENCE
DOI: 10.1126/science.1258410
关键词
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资金
- NASA Exobiology Program
- NSF-ELT program
- California Institute of Technology
- National Science and Engineering Research Council of Canada Discovery Grant
- Natural Resources Canada's GEM Program
- Australian Research Council's Centres of Excellence Program
- Directorate For Geosciences
- Division Of Earth Sciences [1338299] Funding Source: National Science Foundation
- Division Of Earth Sciences
- Directorate For Geosciences [1338810, 1411609, 1144317] Funding Source: National Science Foundation
The oxygenation of Earth's surface fundamentally altered global biogeochemical cycles and ultimately paved the way for the rise of metazoans at the end of the Proterozoic. However, current estimates for atmospheric oxygen (O-2) levels during the billion years leading up to this time vary widely. On the basis of chromium (Cr) isotope data from a suite of Proterozoic sediments from China, Australia, and North America, interpreted in the context of data from similar depositional environments from Phanerozoic time, we find evidence for inhibited oxidation of Cr at Earth's surface in the mid-Proterozoic (1.8 to 0.8 billion years ago). These data suggest that atmospheric O-2 levels were at most 0.1% of present atmospheric levels. Direct evidence for such low O-2 concentrations in the Proterozoic helps explain the late emergence and diversification of metazoans.
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