Enhanced Arctic-Tethys connectivity ended the Toarcian Oceanic Anoxic Event in NW Europe

The Toarcian Oceanic Anoxic Event (T-OAE, c. 182 Ma) represents a major perturbation of the carbon cycle marked by widespread black shale deposition. Consequently, the onset of the T-OAE has been linked to the combined effects of global warming, high productivity, basin restriction and salinity stra...

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Bibliographic Details
Published in:Geological magazine 2020-10, Vol.157 (10), p.1593-1611
Main Authors: van de Schootbrugge, B., Houben, A. J. P., Ercan, F. E. Z., Verreussel, R., Kerstholt, S., Janssen, N. M. M., Nikitenko, B., Suan, G.
Format: Article
Language:English
Subjects:
Age
Anoxia
Arctic Ocean
Asia
assemblages
Basins
biologic evolution
biozones
Carbon
Carbon cycle
chemostratigraphy
Climate change
Cysts
Dinoflagellata
Dinoflagellates
Europe
geochemical cycle
global change
Global warming
Isotopes
Jurassic
Lower Jurassic
Mesozoic
microfossils
Microorganisms
migration
northwestern Europe
Ocean circulation
Ocean models
oceanic anoxic events
Offshore
Original Article
paleo-oceanography
Paleoceanography
paleoecology
paleoenvironment
paleosalinity
Palynology
palynomorphs
Parvocysta
Perturbation
Phallocysta
Pliensbachian
Polar environments
Polar waters
productivity
Records
Salinity
Salinity effects
Salinity stratification
Sea level
Sea level rise
sea-level changes
Sedimentary rocks
Shale
Siberia
Species
stratification
Stratigraphy
Tethys
Toarcian
Viking Corridor
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Summary:The Toarcian Oceanic Anoxic Event (T-OAE, c. 182 Ma) represents a major perturbation of the carbon cycle marked by widespread black shale deposition. Consequently, the onset of the T-OAE has been linked to the combined effects of global warming, high productivity, basin restriction and salinity stratification. However, the processes that led to termination of the event remain elusive. Here, we present palynological data from Arctic Siberia (Russia), the Viking Corridor (offshore Norway) and the Yorkshire Coast (UK), all spanning the upper Pliensbachian – upper Toarcian stages. Rather than a ‘dinoflagellate cyst black-out’, as recorded in T-OAE strata of NW Europe, both the Arctic and Viking Corridor records show high abundance and dinoflagellate diversity throughout the T-OAE interval as calibrated by C-isotope records. Significantly, in the Arctic Sea and Viking Corridor, numerous species of the Parvocysta and Phallocysta suites make their first appearance in the lower Toarcian Falciferum Zone much earlier than in Europe, where these key dinoflagellate species appeared suddenly during the Bifrons Zone. Our results indicate migrations of Arctic dinoflagellate species, driven by relative sea-level rise in the Viking Corridor and the establishment of a S-directed circulation from the Arctic Sea into the Tethys Ocean. The results support oceanographic models, but are at odds with some interpretations based on geochemical proxies. The migration of Arctic dinoflagellate species coincides with the end of the T-OAE and marks the arrival of oxygenated, low-salinity Arctic waters, triggering a regime change from persistent euxinia to more dynamic oxygen conditions.
ISSN:0016-7568
1469-5081
DOI:10.1017/S0016756819001262