Redox conditions and microbial activities in the middle Proterozoic Roper ocean

2016 Fiscal Year Final Research Report

• Project/Area Number: 26400484
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Geology
• Research Institution: Tokyo Institute of Technology
• Principal Investigator: YOSHIYA KAZUMI 東京工業大学, 地球生命研究所, Affiliated Scientist (00636897)
• Project Period (FY): 2014-04-01 – 2017-03-31
• Keywords: 中期原生代 / 酸化還元状態 / McArthur Basin / 窒素同位体比 / 炭素同位体比

Outline of Final Research Achievements

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.

Free Research Field

地球化学