Preprints
https://doi.org/10.5194/egusphere-2023-260
https://doi.org/10.5194/egusphere-2023-260
08 Mar 2023
 | 08 Mar 2023

Warming drove the Expansion of Marine Anoxia in the Equatorial Atlantic during the Cenomanian Leading up to Oceanic Anoxic Event 2

Mohd Al Farid Abraham, Bernhard David A. Naafs, Vittoria Lauretano, Fotis Sgouridis, and Richard D. Pancost

Abstract. Oceanic Anoxic Event (OAE) 2 (~93.5 millions of years ago) is characterized by widespread marine anoxia and elevated burial rates of organic matter. However, the factors that led to this widespread marine deoxygenation and the possible link with climatic change remain debated. Here, we report long-term biomarker records of water column anoxia, water column and photic zone euxinia (PZE), and sea surface temperature (SST) from Demerara Rise in the equatorial Atlantic that span 3.8 million years of the late Cenomanian to Turonian, including OAE 2. We find that total organic carbon (TOC) contents are high but variable (0.41–17 wt. %) across the Cenomanian and increase with time. This long-term TOC increase coincides with a TEX86-derived SST increase from ~ 35 to 40 °C as well as the episodic occurrence of 28,30-dinorhopane (DNH) and lycopane, indicating warming and expansion of the oxygen minimum zone (OMZ) predating OAE 2. Water column euxinia persisted through much of the late Cenomanian, as indicated by the presence of C35 hopanoid thiophene, but only reached the photic zone during OAE 2, as indicated by the presence of isorenieratane. Using these biomarker records, we suggest that water column anoxia and euxinia in the equatorial Atlantic preceded OAE 2 and this deoxygenation was driven by global warming.

Mohd Al Farid Abraham et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-260', Alexandre Pohl, 27 Apr 2023
    • AC1: 'Reply on RC1', Mohd Al Farid Abraham, 22 Sep 2023
  • RC2: 'Comment on egusphere-2023-260', Anonymous Referee #2, 03 Jul 2023
    • AC2: 'Reply on RC2', Mohd Al Farid Abraham, 22 Sep 2023

Mohd Al Farid Abraham et al.

Mohd Al Farid Abraham et al.

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Short summary
Oceanic Anoxic Event (OAE) 2 (~93.5 millions of years ago) is characterized by widespread marine anoxia and elevated burial rates of organic matter. However, the factors that led to this widespread marine deoxygenation and the possible link with climatic change remain debated. We reported a 3.8 million-year record of sea surface temperature rise driven by global warming had caused tropical ocean deoxygenation prior to Oceanic Anoxia Event 2 (93.5 Ma).