Triple oxygen isotope evidence for a hot Archean ocean

Triple oxygen isotope variations in sedimentary rocks

Relatively large (P0.2&) O anomalies in the geologic record have been used to recognize atmospheric processes such as photochemical reactions and to trace changes in the partial pressures of O2 and CO2 in Earth’s atmosphere through time. However, recent oxygen isotope measurements of terrestrial rocks, minerals and waters also reveal common, smaller (but statistically significant) deviations fr...

Cenozoic Climate ^ Oxygen Isotope Evidence

Discoveries of fossil remains of 50 million year old alligators on Ellesmere Island and 30}40 million year-old forests on Antarctica contrast sharply with our present vision of polar climates. These are not isolated discoveries or quirks of nature. An evergrowing body of faunal, Soral, and geochemical evidence shows that the Rrst half of the Cenozoic Era was much warmer than the present time. W...

Iron isotope constraints on the Archean and Paleoproterozoic ocean redox state.

The response of the ocean redox state to the rise of atmospheric oxygen about 2.3 billion years ago (Ga) is a matter of controversy. Here we provide iron isotope evidence that the change in the ocean iron cycle occurred at the same time as the change in the atmospheric redox state. Variable and negative iron isotope values in pyrites older than about 2.3 Ga suggest that an iron-rich global ocea...

Comment on "Iron isotope constraints on the Archean and Paleoproterozoic ocean redox state".

Rouxel et al. (Reports, 18 February 2005, p. 1088) argued that changes in the iron isotopic composition of sedimentary sulfides reflect changes in the oxidation state of the atmosphere-ocean system between 2.3 and 1.8 million years ago. We show that misinterpretations of the origins of these minerals undermine their conclusions.

Iron and carbon isotope evidence for microbial iron respiration throughout the Archean