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Extreme Oligocene cooling in the North American Cordillera

The continental response to global climate forcing remains difficult to predict due to the intricate feedbacks among climate, vegetation and other land surface changes. This is exemplified by the Eocene-Oligocene Transition (EOT; 34 Ma), where a 2-3°C cooling event is observed in marine records around the world, but continental records from the North American Great Plains suggest more extreme cooling of 7-8°C instead. Here we present a new Oligocene record from the adjacent high-elevation North American Cordillera (Cook Ranch section; SW Montana) constrained by four radiometrically dated tuffs. Dual clumped isotopes (Δ47 and Δ48) of this record suggest no major changes in temperature across the EOT, but instead show extreme cooling of 10±1°C in the early Oligocene (32-30 Ma). Based on paleobotanical and climate model data, we interpret this as summer cooling coeval with a decrease in atmospheric CO2 identified in recent proxy compilations. This long-term Oligocene cooling may explain the lack in mammal response observed in North American fossils compared with other continents.

Details

Author
Niels Meijer1, Katharina Methner2, Nikki M. Seymour3, Debra L. Hanneman4, Miguel Bernecker5, Jens Fiebig5, Andreas Mulch6
Institutionen
1Senckenberg Biodiversity and Climate Research Centre (SBiK-F), Frankfurt am Main, Germany; 2Institute of Earth System Science and Remote Sensing, University of Leipzig, Germany; 3Department of Geology, Occidental College, Los Angeles, CA, USA; 4Whitehall GeoGroup Inc., 107 Whitetail Road, Whitehall, Montana 59759, USA; 5Goethe University Frankfurt, Institute of Geosciences, Frankfurt am Main, Germany; 6Senckenberg Biodiversity and Climate Research Centre (SBiK-F), Frankfurt am Main, Germany;Goethe University Frankfurt, Institute of Geosciences, Frankfurt am Main, Germany
Veranstaltung
GeoSaxonia 2024
Datum
2024
DOI
10.48380/q61h-9j02