Carbon isotopic analyses of ca. 3.0 Ga microstructures imply planktonic autotrophs inhabited Earth's early oceans
C.H. House et al., Department of Geosciences and Penn State University Astrobiology Research Center, The Pennsylvania State University, 220 Deike Building, University Park, Pennsylvania 16802, USA. Published online ahead of print on 4 April; http://dx.doi.org/10.1130/G34055.1.
Unusual and surprisingly complex, organic spindle-shaped structures in 3-billion-year-old sediments from Australia are likely the remains of an ancient planktonic life form. Interpretation of these microfossils has been debated due to their relatively large size and great antiquity. The new research, using state-of-the-art instruments, determined the amount of different stable carbon isotopes in fifteen of these microfossils. The results show isotopic compositions that are quite consistent with a biogenic origin and, at the same time, distinct from background carbon in the same rock. These new results also provide some metabolic constraints that imply that the preserved microorganisms fixed carbon from the atmosphere, meaning the cells produced complex organic compounds from carbon dioxide. The existence of similar fossils in even older rocks from South Africa and other localities in Australia suggests that this unusual life form was part of a biological experiment that appears to have been widespread on the early Earth and may have lasted for several hundred million years.
A new paleothermometer for forest paleosols and its implications for Cenozoic climate
Timothy M. Gallagher and Nathan D. Sheldon, Department of Earth and Environmental Sciences, University of Michigan, 2534 CC Little, 1100 N. University Avenue, Ann Arbor, Michigan 48109, USA. Published online ahead of print on 4 April; '/>"/>
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