EGU2020-8642, updated on 12 Jun 2020
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Last 12 ky record of various organic geochemical proxies in the Eastern Arabian Sea

Ayusmati Manaskanya1,2, Aninda Mazumdar2, Aditya Peketi2, Svetlana Fernandes2, and Rheane D. A. Silva2
Ayusmati Manaskanya et al.
  • 1Academy of Scientific and innovative Research (AcSIR), Ghaziabad-201002, India (Email:
  • 2CSIR-National Institute of Oceanography, Dona Paula, Goa-403004, India

Here we present high-resolution biogeochemical study using nitrogen/carbon isotope ratio measurement and molecular proxies from a sediment core (length = 2.9 m) collected from the center (588 mbsl; Lat: 16049.88’N and Long: 710 58.55’ E) of the oxygen minimum zone off west coast of India. The core archives the depositional record covering 1.114 to 12.025 ky BP. The concentrations of total organic carbon (TOC) and total nitrogen (TN) range from 0.7 to 4.9 wt% and 0.068 to 0.5 wt % respectively. TOC and TN show parallel trends and the TOC/TN ratio varies within a narrow range of 8 to 11.5. The δ13C values range from -20.5‰ to -21.9‰ (V-PDB). The TOC/TN and δ13C suggest typical marine organic matter source. This observation is also further supported by the n-alkane distribution pattern where the dominance of nC21 to nC24 and the absence of odd alkane dominance over even suggest predominantly marine organic source. The δ15N profile shows a steady increase from 5.7‰ at 203 cmbsf (5.5 ky BP) to 7.5‰ at 2 cmbsf (~1ky BP) suggesting gradual increase in denitrification possibly liked to reduced ventilation in the Arabian Sea, whereas, between 5.5 to 12 ky BP, the δ15N values show marked fluctuations (5.2 to 7.1‰) possibly indicating variable level of oxygenation which in turn controlled the extent of denitrification. Possible influence of diagenesis (microbial degradation of organic matter) on the δ15N values also need to be investigated for a better understanding of the water column processes.

How to cite: Manaskanya, A., Mazumdar, A., Peketi, A., Fernandes, S., and Silva, R. D. A.: Last 12 ky record of various organic geochemical proxies in the Eastern Arabian Sea, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8642,, 2020


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