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Early Eocene magnetostratigraphy and tectonic evolution of the Xining Basin,NE Tibet |
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| Authors: | Niels Meijer Guillaume Dupont-Nivet Alexis Licht Pierrick Roperch Alexander Rohrmann Aijun Sun Shengcheng Lu Amber Woutersen Norbert Nowaczyk |
| Institution: | 1. Senckenberg Biodiversity and Climate Research Centre (SBiK-F), Frankfurt am Main, Germany;2. Géosciences Rennes - UMR CNRS 6118, Univ Rennes, CNRS, Rennes, France;3. CNRS, IRD, INRAE, CEREGE, Aix Marseille University, Aix-en-Provence, France;4. Institute of Geological Sciences, Freie Universität Berlin, Berlin, Germany;5. Key Laboratory of Western China's Environmental Systems (Ministry of Education), College of Earth and Environmental Sciences, Lanzhou University, Lanzhou, China
Key Laboratory of Desert and Desertification, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou, China University of Chinese Academy of Sciences, Beijing, China;6. School of Urban Construction and Environment, Dongguan City College, Dongguan, China;7. Department of Ecosystem and Landscape Dynamics (ELD), Institute for Biodiversity and Ecosystem Dynamics (IBED), University of Amsterdam, Amsterdam, the Netherlands;8. GFZ German Research Centre for Geosciences, Potsdam, Germany |
| Abstract: | The Cenozoic strata of the Xining Basin, NE Tibet, have provided crucial records for understanding the tectonic and palaeo-environmental evolution of the region. Yet, the age of the lower part of the sedimentary stratigraphy and, consequently, the early tectonic evolution of the basin remain debated. Here, we present the litho- and magnetostratigraphy of various early Eocene sections throughout the Xining Basin independently constrained by the U–Pb radiometric age of a carbonate bed. Our study extends the dated stratigraphy down to 53.0 Ma (C24n.1r) and reveals highly variable accumulation rates during the early Eocene ranging from 0.5 to 8 cm/ka. This is in stark contrast to the low but stable accumulation rates (2–3 cm/ka) observed throughout the overlying Palaeogene and Neogene strata. Such a pattern of basin infill is not characteristic of flexural subsidence as previously proposed, but rather supports an extensional origin of the Xining Basin with multiple depocentres, which subsequently coalesced into a more stable and slowly subsiding basin. Whether this extension was related to the far-field effects of the subducting Pacific Plate or the India–Asia collision remains to be confirmed by future studies. |
| Keywords: | Eocene geochronology northeast Tibet palaeomagnetism stratigraphy Xining Basin |