Book contents
- Frontmatter
- Contents
- List of Contributors
- Preface
- The Proterozoic Biosphere
- PART I
- 1 Geology and Paleobiology of the Archean Earth
- 2 Geological Evolution of the Proterozoic Earth
- 3 Proterozoic Biogeochemistry
- 4 Proterozoic Atmosphere and Ocean
- 5 Proterozoic and Selected Early Cambrian Microfossils: Prokaryotes and Protists
- 6 Modern Mat-Building Microbial Communities: a Key to the Interpretation of Proterozoic Stromatolitic Communities
- 7 Proterozoic and Earliest Cambrian Carbonaceous Remains, Trace and Body Fossils
- 8 The Proterozoic-Early Cambrian Evolution of Metaphytes and Metazoans
- 9 Molecular Phylogenetics, Molecular Paleontology, and the Proterozoic Fossil Record
- 10 Biostratigraphy and Paleobiogeography of the Proterozoic
- 11 Biotic Diversity and Rates of Evolution During Proterozoic and Earliest Phanerozoic Time
- 12 A Paleogeographic Model for Vendian and Cambrian Time
- 13 Evolution of the Proterozoic Biosphere: Benchmarks, Tempo, and Mode
- PART 2
- References Cited
- Subject Index
- Index to Geologic Units
- Taxonomic Index
4 - Proterozoic Atmosphere and Ocean
Published online by Cambridge University Press: 04 April 2011
- Frontmatter
- Contents
- List of Contributors
- Preface
- The Proterozoic Biosphere
- PART I
- 1 Geology and Paleobiology of the Archean Earth
- 2 Geological Evolution of the Proterozoic Earth
- 3 Proterozoic Biogeochemistry
- 4 Proterozoic Atmosphere and Ocean
- 5 Proterozoic and Selected Early Cambrian Microfossils: Prokaryotes and Protists
- 6 Modern Mat-Building Microbial Communities: a Key to the Interpretation of Proterozoic Stromatolitic Communities
- 7 Proterozoic and Earliest Cambrian Carbonaceous Remains, Trace and Body Fossils
- 8 The Proterozoic-Early Cambrian Evolution of Metaphytes and Metazoans
- 9 Molecular Phylogenetics, Molecular Paleontology, and the Proterozoic Fossil Record
- 10 Biostratigraphy and Paleobiogeography of the Proterozoic
- 11 Biotic Diversity and Rates of Evolution During Proterozoic and Earliest Phanerozoic Time
- 12 A Paleogeographic Model for Vendian and Cambrian Time
- 13 Evolution of the Proterozoic Biosphere: Benchmarks, Tempo, and Mode
- PART 2
- References Cited
- Subject Index
- Index to Geologic Units
- Taxonomic Index
Summary
In this Chapter an overview is developed of aspects of the Proterozoic atmosphere and oceans based as much as possible on geologic evidence, but supplemented by theory, whenever such evidence is indirect, incomplete, or lacking. Much of the theoretical treatment is rather oversimplified and speculative. Several biologically important aspects of the Proterozoic environment are addressed, namely, the partial pressures of oxygen and carbon dioxide in the atmosphere and possible changes in their partial pressures as a function of Precambrian time. Aspects of the chemistry and evolution of the Proterozoic ocean are discussed as well.
Banded iron-formations (BIFs) are the most abundant chemical sediments found throughout much of Precambrian time. Because they are generally devoid of clastic components, their chemistry, their oxidation state, and their temporal distribution provide important clues about the chemistry and the chemical evolution of the Precambrian ocean and atmosphere. Section 4.2 provides a synopsis of the average major element chemistry of banded iron-formations throughout the Precambrian; all iron-formations older than about 1.9 Ga represent very similar chemical systems. Iron-formations formed between 0.8 and 0.6 Ga are distinctly different and are more highly oxidized. Few iron-formations are younger than about 1.8 Ga; a minor resurgence in BIF deposition occurred between 0.8 and 0.6 Ga. After about 1.85 Ga, the atmosphere and oceans became rather highly oxygenated and the oceans as a whole became depleted in iron.
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- Information
- The Proterozoic BiosphereA Multidisciplinary Study, pp. 135 - 174Publisher: Cambridge University PressPrint publication year: 1992
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