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Qaidam leaf fossils reveals paleoelevation and paleoclimate of northeastern Tibet in early Oligocene

2020-03-17


The Qaidam Basin in northern Tibet is a key region for understanding the history and the underlying mechanisms of Central Asia aridification because it hosts an extremely thick (12 km) continuous Cenozoic sedimentary succession ranging from the Paleocene to the Quaternary. Abundant sedimentological evidence indicates that a step-wise drying in Central Asia began in the late Eocene and that aridity persists today. Drying has been linked to Cenozoic global cooling, uplift of Tibet associated with India-Asia plate collision, or the retreat of the proto-Paratethy. To understand fully the links between tectonics and climate change requires quantification of past climate as well as a detailed knowledge of the Paleogene topography in the region.



In a recent collaborative research by Dr. Gongle Shi from NIGPAS, Dr. Bowen Song and Professor Kexin Zhang from China University of Geosciences, Wuhan, Professor Robert Spicer from Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences and The Open University, UK, etc., they apply the Climate-Leaf Analysis Multivariate Program (CLAMP) and moist enthalpy method to the newly discovered early Oligocene (30.8 Ma) fossil leaves from the Qaidam Basin, to reconstruct quantitatively the paleoclimate and paleoelevation of this critical part of northern Tibet. The Qaidam Basin floor vegetation is estimated at 3.3 ±1.4 km in the early Oligocene, similar to that of the present basin floor but higher than the rising Himalaya at that time, and experienced a temperate, moderately wet climate. Near-freezing (1.4 ±3.5◦C) winters accompanied cool summers (23 ±2.9◦C). Annual precipitation likely exceeded 1000 mm (growing season precipitation of 1229 ±643 mm) with subdued (non-monsoonal) seasonality in which summers were drier than winters. This finding challenges geodynamic models that envisage a Miocene or later uplift of northern Tibet and progressive uplift from the south.

 

The research was recently published in “Earth and Planetary Science Letters”. This work is funded by the National Natural Science Foundation of China, the Strategic Priority Research Program (B) of Chinese Academy of Sciences, the Youth Innovation Promotion Association, CAS, the Foundation of the Geological Survey of China etc.. 

 

ReferenceSong Bowen*, Spicer R.A., Zhang Kexin*, Ji J., Farnsworth A., Hughes A.C., Yang Y., Han F., Xu Y., Spicer T., Shen T., Lunt D.J., Shi Gongle*, 2020. Qaidam Basin leaf fossils show northeastern Tibet was high, wet and cool in the early Oligocene. Earth and Planetary Science Letters 537, 116175.

Linkhttps://authors.elsevier.com/a/1aey5,Ig4Kpg3


Fig.1. Early Oligocene Qaidam plant fossils




Fig. 2. Rupelian general circulation climate model (GCM) paleogeography and moist enthalpy at sea level.







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