Nitrogen isotope variations and environmental perturbations during Cenomanian-Turonian transition in the NE Tethyan realm, Koppeh-Dagh basin
نویسندگان
1 Department of Geology, Faculty of Science, Ferdowsi University of Mashhad, Mashhad, Iran
2 Department of Geology, Faculty of Science, Ferdowsi University of Mashhad, Mashhad, Iran
3 Department of Geology, Faculty of Science, Ferdowsi University of Mashhad, Mashhad, Iran
4 Department of Geology, Faculty of Science, University of Isfahan, Isfahan, Iran
5 Department of Environmental Changes, Faculty of Social and Cultural Studies, Kyushu University, Fukuoka, Japan
doi
10.22059/geope.2016.59787چکیده
The Cenomanian-Turonian Gharesu section in the east of Kopet-Dagh basin have been investigated to determine the relationship between palaeoenvironmental perturbations and nitrogen cycling across OAE2. This succession is composed of 43 m shale and marl interbedded with glauconitic sandstone and lies between Aitamir-Abderaz formations boundary. The nitrogen Isotope values fluctuate between 0‰ to +3‰ and TOC/TN ratios range from 3.5 to 20.5 in this section. The TOC/TN exhibits high ratios in the organic-rich sediments which were deposited in a low-oxygen environment because nitrogen-rich organic matter was preferably degraded in this condition. The δ15N values are also low in the organic-rich sediments which indicate a nitrogen fixation process as a consequence of greenhouse climate, enhanced productivity and expanded oxygen minimum zone during OAE2.
