The uplift history of southeastern Tibet is crucial to understanding processes driving the tectonic evolution of the Tibetan Plateau and surrounding areas. However, our current understanding of the processes of landscape evolution in the southeastern part of theHimalaya-Tibet Edifice (HTE) has been undermined. Then, the elevation history of the Tibetan Plateau is one of collisional modification of a large pre-existing area of high and complex topography.
Researchers from Xishuangbanna Tropical Botanical Garden (XTBG) and their collaborators used radiometrically dated plant fossil assemblages to seek uplift, climate and biotic changes at the Eocene-Oligocene transition in southeast Tibet. They got their research result published inNational Science Review.
The researchers attempted to quantify when southeastern Tibet achieved its present elevation, and what kind of floras existed there at that time. They employed well-dated fossil floras and used a technique independent of isotope fractionation models and lapse rates.
With new radiometric dating and newly-collected plant fossil archives, they quantified the surface height of part of Tibet's southeastern margin of Tibet in the latest Eocene (i.e. about 34 million years ago) to be about 3 km and rising, possibly attaining its present elevation (3.9 km) in the early Oligocene.
The result demonstrated clearly that the early onset of uplift in southeastern Tibet, rather than a later during the later Oligocene and Neogene.
They also found that the Eocene-Oligocene transition in southeastern Tibet witnessed leaf size diminution and a floral composition change from sub-tropical/warm temperate to cool temperate.
Their findings show that the elevation of southeastern Tibet took place largely prior to the Oligocene, which has major implications for uplift mechanisms, landscape development and biotic evolution, countering arguments for a Neogene onset of lower crustal flow, uplift and river incision.
Prof. ZHOU Zhekun Ph.D
Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, China