Authors:  Yuan Q., Barbolini N., Rydin C., Gao D.-L., Wei H.-C., Fan Q.-S., Qin Z.-J., Du Y.-S., Shan J.-J., Shan F.-S., Vajda V.
Journal: Climate of the Past


Central Asia experienced a number of significant elevational and climatic changes during the Cenozoic, but much remains to be understood regarding the timing and driving mechanisms of these changes, as well as their influence on ancient ecosystems. Here we describe the palaeoecology and palaeoclimate of a new section from the Nangqian Basin in Tibet, northwestern China, here dated as late Lutetian–Bartonian (late middle–late Eocene) based on our palynological analyses. Located on the east-central part of the Tibetan Plateau, this section is excellently placed for better understanding the palaeoecological history of Tibet following the India-Asia collision. Our new pollen record reveals that a strongly seasonal steppe-desert ecosystem characterised by drought-tolerant shrubs, diverse ferns and an underlying component of broad-leaved forests existed in east-central Tibet during the Eocene, influenced by a southern monsoon. Warming during the Middle Eocene Climatic Optimum only prompted a temporary vegetation response, while a drying signature in our pollen record after 40 Ma demonstrates that proto-Paratethys sea retreat caused widespread long-term aridification across the plateau. To better distinguish between local climatic variation and farther-reaching drivers of Central Asian palaeoclimate and elevation, we correlated key palynological sections across the Tibetan Plateau by means of established radioisotopic ages and biostratigraphy. This new palynozonation illustrates both intra- and inter-basinal floral response to plateau uplift and global climate change during the Paleogene, and provides a framework for the age assignment of future palynological studies in Central Asia. Our work highlights the ongoing challenge of integrating various deep time records for the purpose of reconstructing palaeoelevation, indicating that a multiproxy approach is vital for unravelling the complex uplift history of the Tibetan Plateau and its resulting influence on Asian climate.