First evidence of denitrification vis-\xe0-vis monsoon in the Arabian Sea since Late Miocene

Shubham Tripathi,Hannah M Liddy,Manish Tiwari,Dhananjai K Pandey,A Ganesh Kumar,Ravi Mishra,Stephan Steinke,Zuyan Xu ,Masao Iwai,Annette Hahn,R K Saxena ,Rajeev Saraswat,Sophia Aharonovich,Sergio Andó ,Denise K Kulhanek,Mitchell W Lyle ,Arun D Singh,Huayu Lu,T Radhakrishna ,Girish Kumar Sharma ,Peter D Clift,G P Gurumurthy ,James Bendle ,Lisa Tauxe,Giancarlo Scardia,Elizabeth M Griffith,Kenta Suzuki,Jongmin Lee,Anil Kumar,Claire M Routledge,Boo‐Keun Khim ,Zhaojie Yu

doi:10.1038/srep43056

Shubham Tripathi, Hannah M Liddy + Show 30 more

Open Access

https://doi.org/10.1038/srep43056

Copy DOI

Abstract

In the Arabian Sea, South Asian monsoon (SAM)-induced high surface water productivity coupled with poor ventilation of intermediate water results in strong denitrification within the oxygen minimum zone (OMZ). Despite the significance of denitrification in the Arabian Sea, we have no long-term record of its evolution spanning the past several million years. Here, we present the first record of denitrification evolution since Late Miocene (~10.2 Ma) in the Eastern Arabian Sea, where the SAM generates moderate surface water productivity, based on the samples retrieved during the International Ocean Discovery Program (IODP) Expedition 355. We find that (i) the SAM was persistently weaker from ~10.2 to 3.1 Ma; it did not intensify at ~8 Ma in contrast to a few previous studies, (ii) on tectonic timescale, both the SAM and the East Asian Monsoon (EAM) varied synchronously, (iii) the first evidence of denitrification and productivity/SAM intensification was at ~3.2–2.8 Ma that coincided with Mid-Pliocene Warm Period (MPWP), and (iv) the modern strength of the OMZ where denitrification is a permanent feature was attained at ~1.0 Ma.

Highlights

We present the first record of denitrification evolution since Late Miocene (~10.2 Ma) in the Eastern Arabian Sea, where the South Asian monsoon (SAM) generates moderate surface water productivity, based on the samples retrieved during the International Ocean Discovery Program (IODP) Expedition 355
We find that (i) the SAM was persistently weaker from ~10.2 to 3.1 Ma; it did not intensify at ~8 Ma in contrast to a few previous studies, (ii) on tectonic timescale, both the SAM and the East Asian Monsoon (EAM) varied synchronously, (iii) the first evidence of denitrification and productivity/SAM intensification was at ~3.2–2.8 Ma that coincided with MidPliocene Warm Period (MPWP), and (iv) the modern strength of the oxygen minimum zone (OMZ) where denitrification is a permanent feature was attained at ~1.0 Ma
The drilled section at Site U1456 is divided into four lithologic units based on a variety of sediment properties (Fig. 2a); Unit I (~121 m thick and Pleistocene nannofossil ooze interbedded with very thin turbidites), Unit II (~240 m thick and late Pliocene to early Pleistocene sand and silt), Unit III (~370 m thick and late Miocene to late Pliocene clay/claystone, sand/sandstone, nannofossil chalk, and nannofossil-rich claystone), and Unit IV (~380 m thick and older than late Miocene claystone, calcarenite, calcilutite, and conglomerate/breccia)

Summary

University of Birmingham

First evidence of denitrification vis-à-vis monsoon in the Arabian Sea since Late Miocene Document Version Publisher's PDF, also known as Version of record Citation for published version (Harvard): IODP Expedition 355 Scientists 2017, 'First evidence of denitrification vis-à-vis monsoon in the Arabian Sea since Late Miocene', Scientific Reports, vol 7, 43056. https://doi.org/10.1038/srep43056

Link to publication on Research at Birmingham portal

Study Area

Results and Discussion

Methods

Author Contributions

Additional Information