The topographic evolution of the Tibetan Region as revealed by palaeontology
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ORIGINAL PAPER
The topographic evolution of the Tibetan Region as revealed by palaeontology Robert A. Spicer 1,2,3 & Tao Su 1,2 & Paul J. Valdes 4 & Alexander Farnsworth 4 & Fei-Xiang Wu 5 & Gongle Shi 6 & Teresa E. V. Spicer 1 & Zhekun Zhou 1,2 Received: 22 February 2020 / Revised: 14 May 2020 / Accepted: 2 September 2020 # The Author(s) 2020
Abstract The Tibetan Plateau was built through a succession of Gondwanan terranes colliding with Asia during the Mesozoic. These accretions produced a complex Paleogene topography of several predominantly east–west trending mountain ranges separated by deep valleys. Despite this piecemeal assembly and resultant complex relief, Tibet has traditionally been thought of as a coherent entity rising as one unit. This has led to the widely used phrase ‘the uplift of the Tibetan Plateau’, which is a false concept borne of simplistic modelling and confounds understanding the complex interactions between topography climate and biodiversity. Here, using the rich palaeontological record of the Tibetan region, we review what is known about the past topography of the Tibetan region using a combination of quantitative isotope and fossil palaeoaltimetric proxies, and present a new synthesis of the orography of Tibet throughout the Paleogene. We show why ‘the uplift of the Tibetan Plateau’ never occurred, and quantify a new pattern of topographic and landscape evolution that contributed to the development of today’s extraordinary Asian biodiversity. Keywords Tibet . Himalaya . Hengduan Mountains . Palaeoaltimetry . Fossils . Climate
Introduction The modern Tibetan Plateau (Fig. 1) is the highest and most extensive elevated surface on Earth covering an area of 2,500,000 km2at an average elevation above 4500 m. The boundaries of the plateau extend 1000 km northwards from the Yarlung–Tsangpo suture zone (YTSZ), south of which is the Himalayan thrust belt, to the Altyn Tagh fault. Westwards the plateau boundary is marked by the Karakoram strike–slip
fault, while 2000 km to the east the plateau morphs into the Hengduan Mountains and down into Yunnan and Sichuan. In conjunction with the adjacent Himalaya and Hengduan Mountain systems (Fig. 1), the Tibetan Plateau is often referred to as ‘The Third Pole’ (Qiu 2008) and regarded as the ‘Water Tower’ (Viviroli et al. 2007; Immerzeel et al. 2020) of Asia. This is because its hydrological services, delivered through the Yangtse, Yellow, Red, Mekong, Salween, Tsangpo–Brahmaputra, Indus and Ganges rivers that all
This article is a contribution to the special issue Palaeobotanical contributions in honour of Volker Mosbrugger * Robert A. Spicer [email protected] 1
CAS Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla 666303, China
2
Center of Plant Ecology, Core Botanical Gardens, Chinese Academy of Sciences, Mengla 666303, China
3
School of Environment, Earth and Ecosystem Sciences, The Open University, Milton Keynes MK7 6AA, UK
4
School of Geographical Sciences, Universi
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