Late early Oligocene East Asian summer monsoon in the NE Tibetan Plateau: Evidence from a palynological record from the Lanzhou Basin,China |
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| Institution: | 1. The Key Laboratory of Desert and Desertification, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, China;2. BFU—Buero für Umwelttechnologien GmbH, Gelnhausen, Germany;1. State Key Laboratory of Biocontrol and Guangdong Provincial Key Laboratory of Plant Resources, School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, China;2. Geological Institute, Russian Academy of Sciences, Moscow 119017, Russia;3. Environment, Earth, Ecosystems, The Open University, Milton Keynes MK7 6AA, UK;4. State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China;5. Borissiak Paleontological Institute, Russian Academy of Sciences, Moscow 117647, Russia;1. Research Center of Paleontology and Stratigraphy, Jilin University, Changchun 130026, China;2. Department of Earth Sciences, The University of Hong Kong, Hong Kong, China;3. Steinmann Institute, Bonn University, Bonn 53115, Germany;4. Senckenberg Research Institute, Frankfurt 60325, Germany;5. School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, China;6. State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China;7. School of Earth Sciences and Engineering, Nanjing University, Nanjing 210093, China;8. Department of Biological Sciences and Don Sundquist Center of Excellence in Paleontology, East Tennessee State University, Johnson City, TN 37614, USA |
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| Abstract: | The latest Early Oligocene record from the Lanzhou Basin, northeast Tibetan Plateau, presents an opportunity to investigate early stage of the Asian monsoon patterns due to its special location. The record provides insights into the global zonal climate and the development of the non-zonal monsoon system. The study identifies possible links between factors governing the monsoonal patters and paleoaltimetry of the Tibetan Plateau. Sporomorphs results indicate the dominance of arboreal plants (both coniferous and broad-leaved) corresponding to a wetter environment, while xerophytes were rare. Based on the Coexistence Approach (CA), the climate of the Lanzhou Basin is likely to have been similar to that of present-day sites in Southeast China, i.e., characterized by relatively high precipitation and a warm climate. Both qualitative analysis of the sporomorph assemblages and quantitative calculations indicate that monsoons similar to those of the present daywere formed in East Asia and reached the Lanzhou region in inner Asia. High percentages of Picea, generally associated with the relatively high topography of the NE Tibetan Plateau, correlate well with the high paleoaltimetry of the main Tibetan Plateau during the Oligocene. Thus, the East Asian monsoon during this time can be closely linked to an uplifted Tibetan Plateau, following modeled relationships between the Tibetan Plateau and monsoon patterns. However, we believe such high precipitation may have mainly resulted from the orographic barrier, rather than being driven by zonal climate factors. Further investigation into the extent of, and controls on, the region of high precipitation should help clarify the role of these processes. |
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| Keywords: | Oligocene Sporopollen East Asian monsoon Tibetan Plateau |
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