Oceanic redox conditions through the late Pliensbachian to early Toarcian on the northwestern Panthalassa margin

Insights from pyrite and geochemical data

Kentaro Izumi*, Kasumi Endo, David B. Kemp, Mutsuko Inui

*Corresponding author for this work

Research output: Contribution to journalArticle

3 Citations (Scopus)
4 Downloads (Pure)

Abstract

The early Toarcian oceanic anoxic event (T-OAE; ∼. 183. Ma) was a significant palaeoenvironmental perturbation associated with marked changes in oceanic redox conditions. However, the precise redox conditions and redox history of various water masses during the T-OAE, especially those from outside the Boreal and Tethyan realms, are unclear. To address this issue, we present pyrite framboid data from an upper Pliensbachian to lower Toarcian succession deposited on the NW Panthalassa margin in a shallow-water setting (Sakuraguchi-dani section, Toyora area, SW Japan). Available data on lithofacies and redox-sensitive trace elements from the same succession suggest that dysoxic bottom-water conditions generally prevailed, with intermittent short-term oxygenation events. Size-distribution analysis of pyrite framboids reveals that framboid size populations from the silty mudstones during the T-OAE were characterized by small mean diameters and standard deviations. This suggests that euxinic conditions at least intermittently occurred during the T-OAE interval. Most likely, this water-column euxinia was associated with the expansion of an oxygen minimum zone linked to increased primary productivity. This interpretation is consistent with a previously reported increase in fluvial discharge and thus nutrient flux caused by a strengthening of the hydrological cycle.

Original languageEnglish
Pages (from-to)1-10
Number of pages10
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Volume493
Early online date29 Dec 2017
DOIs
Publication statusPublished - 15 Mar 2018

Fingerprint

Pliensbachian
Toarcian
redox conditions
pyrite
oxygenation
hydrological cycle
lithofacies
bottom water
water mass
mudstone
population size
shallow water
water
water column
perturbation
trace element
productivity
oxygen
nutrient
hydrologic cycle

Keywords

  • Euxinia
  • Japan
  • Pyrite framboid
  • Toyora Group
  • Trace element
  • Vanadium

ASJC Scopus subject areas

  • Oceanography
  • Ecology, Evolution, Behavior and Systematics
  • Earth-Surface Processes
  • Palaeontology

Cite this

Oceanic redox conditions through the late Pliensbachian to early Toarcian on the northwestern Panthalassa margin : Insights from pyrite and geochemical data. / Izumi, Kentaro; Endo, Kasumi; Kemp, David B.; Inui, Mutsuko.

In: Palaeogeography, Palaeoclimatology, Palaeoecology, Vol. 493, 15.03.2018, p. 1-10.

Research output: Contribution to journalArticle

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abstract = "The early Toarcian oceanic anoxic event (T-OAE; ∼. 183. Ma) was a significant palaeoenvironmental perturbation associated with marked changes in oceanic redox conditions. However, the precise redox conditions and redox history of various water masses during the T-OAE, especially those from outside the Boreal and Tethyan realms, are unclear. To address this issue, we present pyrite framboid data from an upper Pliensbachian to lower Toarcian succession deposited on the NW Panthalassa margin in a shallow-water setting (Sakuraguchi-dani section, Toyora area, SW Japan). Available data on lithofacies and redox-sensitive trace elements from the same succession suggest that dysoxic bottom-water conditions generally prevailed, with intermittent short-term oxygenation events. Size-distribution analysis of pyrite framboids reveals that framboid size populations from the silty mudstones during the T-OAE were characterized by small mean diameters and standard deviations. This suggests that euxinic conditions at least intermittently occurred during the T-OAE interval. Most likely, this water-column euxinia was associated with the expansion of an oxygen minimum zone linked to increased primary productivity. This interpretation is consistent with a previously reported increase in fluvial discharge and thus nutrient flux caused by a strengthening of the hydrological cycle.",
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note = "Part of this work was financially supported by JSPS grants 15J08821 to KI. DBK acknowledges receipt of NERC Fellowship NE/I02089X/1, and grants from the Great Britain Sasakawa Foundation: grant number 4883 and Daiwa Anglo-Japanese Foundation: grant number 10960/12369. This study contributes to IGCP 655. We thank M. Ikeda, T. Ohta, K. Suzuki, S. Itamiya, and K. Kawano for assistance in the field and/or helpful discussion. Fieldwork was carried out with full permission and support from its landowners. Technical staff at Geo-Science Laboratory (Chikyu Kagaku Kenkyusho) are thanked for performance of TOC and carbon-isotope analysis.",
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