EGU2020-8597
https://doi.org/10.5194/egusphere-egu2020-8597
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Intensified hydrological cycle during the Early Eocene Climatic Optimum (EECO) recorded in the Xining Basin, NE Tibet

Niels Meijer1, Guillaume Dupont-Nivet1,2,3, Alexis Licht4, Pierrick Roperch2, Alexander Rohrmann5, Amber Woutersen6, Carina Hoorn6, Natasha Barbolini7, Aijun Sun8, Hemmo Abels9, Hanno Meyer10, and Norbert Nowaczyk11
Niels Meijer et al.
  • 1Universität Potsdam, Institute of Geosciences, Potsdam-Golm, Germany (meijer@uni-potsdam.de)
  • 2Univ Rennes, CNRS, Géosciences Rennes - UMR CNRS 6118, F-35000 Rennes, France
  • 3Key Laboratory of Orogenic Belts and Crustal Evolution, Ministry of Education, Beijing, China
  • 4Department of Earth and Space Sciences, University of Washington, Seattle, USA
  • 5Tektonik und Sedimentäre Systeme, Freie Universität Berlin, Berlin, Germany
  • 6Department of Ecosystem and Landscape Dynamics (ELD), Institute for Biodiversity and Ecosystem Dynamics (IBED), University of Amsterdam, Amsterdam, the Netherlands
  • 7Department of Ecology, Environment, and Plant Sciences & Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden
  • 8Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining, 810008 China
  • 9Department of Geosciences and Engineering, Delft University of Technology, Delft, the Netherlands
  • 10Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Research Unit Potsdam, Potsdam, Germany
  • 11GFZ German Research Centre for Geosciences, Potsdam, German

The evolution of Asian climate during the Cenozoic is traditionally linked to shifts in paleogeography such as the proto-Paratethys Sea incursions and uplift of the Tibetan Plateau driving monsoonal circulation and affecting the mid-latitude westerlies in Central Asia. In contrast, the role of global climate in the Asian hydrological cycle remains unclear. Here, we present a new stratigraphic record from the terrestrial Xining Basin in central China, which covers the Early Eocene Climatic Optimum (EECO), a period characterized by long-term global warmth and elevated atmospheric CO2 levels. The record is dated using magnetostratigraphy and extends the previously studied Paleogene strata down to 50.9 Ma (chron C23n). We use a variety of paleoclimate proxies, to derive the hydroclimatic evolution of the basin at this time. The lithostratigraphy is characterized by organic-rich mudrocks and gypsum beds (reaching TOC contents of up to 1.7%) interpreted as an alluvial mudflat to saline lake. The higher organic content of the strata indicates either increased organic productivity or preservation, both of which suggest a wetter depositional environment during the EECO. This is corroborated by palynological records showing a large increase in the abundance and diversity of trilete spores, indicating a wetter biome at this time. In addition, the d13C values of the bulk organic matter and leaf waxes (both C29 and C31), suggest a reduction in water stress on plants and a wetter environment as well. These observations are in stark contrast to the arid red beds, evaporites and xerophytic pollen observed in the underlying Cretaceous-Paleocene strata and overlying middle-late Eocene deposits. The peak global warmth of the EECO is thus clearly linked to an intensified Asian hydrological cycle suggesting a major driving role for global climate.

 

How to cite: Meijer, N., Dupont-Nivet, G., Licht, A., Roperch, P., Rohrmann, A., Woutersen, A., Hoorn, C., Barbolini, N., Sun, A., Abels, H., Meyer, H., and Nowaczyk, N.: Intensified hydrological cycle during the Early Eocene Climatic Optimum (EECO) recorded in the Xining Basin, NE Tibet, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8597, https://doi.org/10.5194/egusphere-egu2020-8597, 2020