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A new model for Proterozoic ocean chemistry
There was a significant oxidation of the Earth's surface around 2 billion years ago (2 Gyr). Direct evidence for this oxidation comes, mostly, from geological records of the redox-sensitive elementsExpand
▪ Abstract This paper reviews the Precambrian history of atmospheric oxygen, beginning with a brief discussion of the possible nature and magnitude of life before the evolution of oxygenicExpand
The Evolution and Future of Earth’s Nitrogen Cycle
Humans must modify their behavior or risk causing irreversible changes to life on Earth, as the damage done by humans to the nitrogen economy of the planet will persist for decades, possibly centuries, if active intervention and careful management strategies are not initiated. Expand
Reactive iron in marine sediments.
  • D. Canfield
  • Geology, Medicine
  • Geochimica et cosmochimica acta
  • 1 March 1989
It appears that distinct microenvironments may exist in marine sediments, where, in one microenvironment, sulfide reacts with Fe oxides locally precipitating Fe sulfide minerals, and in another, Fe reduced and solubilized by microorganisms migrates freely into solution. Expand
Development of a sequential extraction procedure for iron: implications for iron partitioning in continentally derived particulates
Abstract The development of a sequential extraction procedure for iron in modern and ancient sediments is presented. The scheme recognizes seven operationally derived iron pools: (1) carbonateExpand
Late Proterozoic rise in atmospheric oxygen concentration inferred from phylogenetic and sulphur-isotope studies
The evolution of non-photosynthetic sulphide-oxidizing bacteria was contemporaneous with a large shift in the isotopic composition of biogenic sedimentary sulphides between 0.64 and 1.05 billionExpand
The global carbon cycle: a test of our knowledge of earth as a system.
It is concluded that although natural processes can potentially slow the rate of increase in atmospheric CO2, there is no natural "savior" waiting to assimilate all the anthropogenically produced CO2 in the coming century. Expand
Biogeochemistry of Sulfur Isotopes
Sulfur, with an atomic weight of 32.06, has four stable isotopes. By far the most abundant is 32S, representing around 95% of the total sulfur on Earth. The next most abundant isotope is 34S,Expand
Atmospheric oxygenation three billion years ago
The findings suggest that there were appreciable levels of atmospheric oxygen about 3 billion years ago, more than 600 million years before the Great Oxidation Event and some 300–400 million years earlier than previous indications for Earth surface oxygenation. Expand
Late-Neoproterozoic Deep-Ocean Oxygenation and the Rise of Animal Life
The iron content of deep-sea sediments shows that the deep ocean was anoxic and ferruginous before and during the Gaskiers glaciation 580 million years ago and that it became oxic afterward. Expand