Grant-in-Aid for Scientific Research (C)
We focused on the relationship between redox conditions and N cycle using the analysis of N and C isotope compositions of middle Proterozoic sedimentary rocks from the McArthur Basin in Australia. The average δ15NTN value of oxic and anoxic sediments is 2.5 and 2.6‰ respectively, suggesting the occurrences of water column denitrification regardless of redox conditions. It means that the isotopic signature of the aerobic N cycle is seen in shallow photic zone even in offshore environments. And, the difference in distribution pattern of C/N atomic ratios related to redox conditions was observed in the Roper Group. In oxic conditions, C/N atomic ratios of samples were lower than 20, whereas those in anoxic conditions were up to 69. The high TOC/TN ratio might be explained by the accumulation of N-depleted bio-molecules. The distribution pattern of microfossils and biomaker studies in the Roper strata are consistent with our speculation of habitat segregation of microorganisms.
Palaeogeography, Palaeoclimatology, Palaeoecology
Geochemistry, Geophysics, Geosystems-G3
Geochimica et Cosmochimica Acta
Gondwana Res. 25, 1027-1044.
Earth and Planetary Science Letters
Applied and Environmental Microbiology
Journal of Asian Earth Sciences
Global Planetary Change
Attribution of KAKENHI