Intrashelf basin record of redox and productivity changes along the Arabian margin of Neo-Tethys during Oceanic Anoxic Event 1a

Jafarian, Arman; Husinec, Antun; Wang, Chengshan; Chen, Xi; Wang, Meng; Gröcke, Darren R.; Saboor, Abdus; Li, Yalin

Abstract

The biotic, environmental, climatic, oceanic, and sea-level perturbations during the Early Aptian Oceanic Anoxic Event (OAE) 1a have been extensively documented from both deep- and shallow-marine deposits worldwide. However, there has been relatively little comparative assessment of the simultaneous interplay among organic carbon burial, redox conditions, terrigenous output, and productivity, leading to a lack of precise constraints on these relationships. Here, we use analyses of stable carbon isotopes (δ13Corg, δ13Ccarb, and Δ13C), total organic carbon (TOC), detrital proxies (Al, Si, Ti, K), redox-sensitive (RSTE: U, V, Mo) and productive-sensitive (PSTE: P, Cu, Ni) trace elements from a continuous, predominantly carbonate succession of the Kazhdumi Intrashelf Basin to evaluate the culprits for the OAE1a-associated changes in bottom-water oxygenation, organic-rich layer formation, and biotic shifts along the Arabian margin of the Neo-Tethys. Concentrations of Al-normalized RSTE and TOC values indicate that the bottom water conditions ranged from oxic prior to and at the onset of the OAE 1a (carbon-isotope segments C2 to basalmost C4 sensu Menegatti et al., 1998), to anoxic-suboxic but not euxinic (Mo < 25 ppm) during the lower C4 through C5 + C6 segments, and then returned to oxic-suboxic in the remaining C5 + C6 segment. The increase in Al-normalized PSTE coupled with TOC concentrations in the basal C4 is coeval with a change from predominantly orbitolinid-ostreid to planktic foraminifera-radiolarian biota. The periodically high productivity, driven both by the surface-water productivity as well as by phosphorus recycling from the sediments, continued through the C5 + C6 segments as evidenced by matching Si/Al and PSTE peaks (Cu/Al and Ni/Al). The study sheds new light on the causes of variations in bottom-water deoxygenation, organic content, nutrient availability, and biotic shifts in semi-restricted, relatively deep (>100 m), continental-margin basins during major oceanic perturbations.

Citation

Jafarian, A., Husinec, A., Wang, C., Chen, X., Wang, M., Gröcke, D. R., …Li, Y. (2024). Intrashelf basin record of redox and productivity changes along the Arabian margin of Neo-Tethys during Oceanic Anoxic Event 1a. Palaeogeography, Palaeoclimatology, Palaeoecology, 636, Article 111975. https://doi.org/10.1016/j.palaeo.2023.111975

• Journal Article Type: Article
• Acceptance Date: Dec 12, 2023
• Online Publication Date: Dec 15, 2023
• Publication Date: Feb 15, 2024
• Deposit Date: Feb 29, 2024
• Publicly Available Date: Feb 29, 2024
• Journal: Palaeogeography, Palaeoclimatology, Palaeoecology
• Print ISSN: 0031-0182
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 636
• Article Number: 111975
• DOI: https://doi.org/10.1016/j.palaeo.2023.111975
• Public URL: https://durham-repository.worktribe.com/output/2290727