EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

A new record of the Toarcian oceanic anoxic event from Scotland (UK) and environmental responses

Wenhan Chen1, David Bryan Kemp1, Tianchen He2, and Chunju Huang1
Wenhan Chen et al.
  • 1School of Earth and Science, China University of Geosciences, Wuhan, China (
  • 2School of Earth and Environment, University of Leeds, Leeds, UK (

The early Toarcian oceanic anoxic event (T-OAE, ~183 Ma) was characterized by a prominent environmental perturbation, likely associated with a large amount of 12C-enriched carbon released into the global ocean-atmosphere system. This effusion caused a marked disruption to the global carbon cycle and propagated a series of remarkable changes in ocean chemistry and climate. Although the T-OAE has been recognized worldwide, clear geographic differences in the character of the event and its environmental effects have been recognized. Here, we present new geochemical data from a lower Toarcian succession on the Isle of Raasay, NE Scotland (Hebrides Basin, Northwest European Shelf). Organic carbon isotope data through the Raasay section reveal a pronounced negative excursion, similar to that recognised globally. The excursion interval is enriched in organic matter, and redox sensitive element data suggest that suboxic bottom water conditions contemporaneously occurred, likely interspersed with anoxic episodes. Our findings contrast with evidence of more pervasive anoxia/euxinia in nearby basins, and emphasize how deoxygenation was spatially variable within the T-OAE. Inorganic geochemical data and sedimentological observations suggest a significant enhancement in chemical weathering and coarse-grained detrital flux during the T-OAE on Raasay. These findings support evidence from other localities for a strengthening of hydrological cycling in response to global warming during the T-OAE.

How to cite: Chen, W., Kemp, D. B., He, T., and Huang, C.: A new record of the Toarcian oceanic anoxic event from Scotland (UK) and environmental responses, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-893,, 2021.

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