Late Proterozoic rise in atmospheric oxygen concentration inferred from phylogenetic and sulphur-isotope studies

Article Abstract:

The timing of the evolution of non-photosynthetic sulphur (S)-oxidizing bacteria and changes in stable S isotopes indicates that these events were caused by a large increase in the atmospheric oxygen during late Proterozoic. The oxygen levels increased to more than 5 to 18% of the present atmospheric level and this permitted the development of an oxidative S cycle and bacterial evolution. Analysis of the 16S rRNA of gamma-proteobacteria shows that they evolved almost 0.76 billion years (Gyr) ago. A significant change in the S isotope composition took place between 0.64 to 1.05 Gyr ago.

Environmental aspects, Oxygen, Isotopes, Paleontology, Sulfur, Proterozoic Eon

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Oil preserved in fluid inclusions in Archaean sandstones

Article Abstract:

Oil is thermodynamically unstable if subject to high temperatures in open systems for a long time, and this has led to a view that it is geologically young. Petroleum production tends to come from young rocks, but there is some evidence that older rocks generated hydrocarbons during their early history. Oil that is very old could be a potential source of information on the diversity and size of the biosphere in its early days. This is especially true if molecular fossils are contained in very old oil.

Analysis, Geological research, Petroleum research

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Isotopic evidence for microbial sulphate reduction in the early Archaean era

Article Abstract:

Research is presented concerning the discovery of microscopic sulphides in 3.47-Gyr-old barite rocks from the Dresser Formation at North Pole, Australia. The evidence for an early specific metabolic pathway is discussed.

Australia, Natural history, Barite

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