5:15 PM - 6:30 PM
[BPT05-P11] Organic Nitrogen/Carbon isotope ratios from the Middle Proterozoic sedimentary rocks, McArthur Basin, Northern Australia
Keywords:Nitrogen isotope ratio, Middle Proterozoic, McArthur Basin
Here we show nitrogen and carbon isotope compositions of middle Proterozoic sediments, mainly carbonate rocks, mudstones and black shales prepared from six drillcore samples (Mount Young 2, McArthur River 2, Urapunga 4, Urapunga 5, Jamison-1 and 14MCDDH002) in McArthur Basin, Northern Australia.
δ15NTN values of the black shale in the Wollogorang and Barney Creek formations are relatively high, ranging from +4 to +7 ‰. The high δ15NTN values likely reflect the predominance of partial denitrification in the water-column. δ15NTN values gradually decrease from +7 to +1 ‰ stratigraphically upward, and the average δ15NTN value is 3.5 ‰.
An increasing nitrate reservoir may have been responsible for the decreasing δ15NTN value, which implying an ocean oxygenation in the middle Proterozoic.