EGU21-9571
https://doi.org/10.5194/egusphere-egu21-9571
EGU General Assembly 2021
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Climate changes across Oceanic Anoxic Event 1a: new data from the Boreal realm

Stephane Bodin1, Carlette Blok1, Jon Ineson2, Kresten Anderskouv3, Alicia Fantasia1, Emma Sheldon2, Nicolas Thibault3, and Thierry Adatte4
Stephane Bodin et al.
  • 1Aarhus University, Department of Geoscience, Denmark (stephane.bodin@geo.au.dk)
  • 2Geological Survey of Denmark and Greenland (GEUS), Copenhagen, Denmark
  • 3Department of Geosciences and Natural Resource Management, University of Copenhagen, Denmark
  • 4Institute of Earth Sciences, University of Lausanne, Switzerland
Our understanding of the climatic evolution during the early Cretaceous in general, and the Oceanic Anoxic Event 1a (OAE-1a) in peculiar, is widely derived from the investigation of Tethyan localities, leaving large uncertainties about their significance on a global scale. In this study, we have performed high-resolution clay-mineral assemblage analyses in the upper Hauterivian to lower Aptian of the North Jens-1 core, located in the Danish central graben that was part of the Boreal realm. High amount of detrital Kaolinite is observed throughout the core, indicating the presence of a local, kaolinite-rich source. A long-term decline in Kaolinite content is occurring from the lower Hauterivian to the lowermost, pre-OAE-1a Aptian, followed by a sharp rise within the OAE-1a. This trend is similar to the one observed in the Tethyan realm, indicating a supra-regional climatic evolution from humid conditions in the late Hauterivian toward drier conditions in the latest Barremian – earliest Aptian, followed by renewed humid conditions during the unfolding of OAE-1a. Precise timing of climate change during the OAE-1a differs however in between the Tethyan and Boreal realm. Shift toward humid conditions coincides hence with the onset of OAE-1a (segment C3) in the Tethyan realm, followed by a return to drier conditions in the second half of OAE-1a. In the Boreal realm, the onset of OAE-1a is characterized by a relatively dry climate, followed by the installation of humid climate during the mid-OAE-1a (segments C4-C5) that persists through the remainder of the early Aptian. Across latitudinal belts, there is thus a non-linear change in precipitation pattern during the unfolding of OAE-1a. Similar observations have been made for other OAEs, suggesting more complex weathering feedback mechanism during hyperthermal events than generally assumed.

How to cite: Bodin, S., Blok, C., Ineson, J., Anderskouv, K., Fantasia, A., Sheldon, E., Thibault, N., and Adatte, T.: Climate changes across Oceanic Anoxic Event 1a: new data from the Boreal realm, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9571, https://doi.org/10.5194/egusphere-egu21-9571, 2021.

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