Fossilised palm leaves give new insights into the geographical landscape of prehistoric central Tibet

A team of scientists from the UK and China have uncovered new evidence, using recently-discovered 25-million-year-old fossilised palm leaves, that Tibet's geography was not as 'high and dry' as previously thought. The new research, co-authored by academics from the University of Bristol's School of Geographical Sciences , suggests that central Tibet must have been no higher than 2.3km with large lakes fringed with subtropical vegetation and deep, hidden valleys. Geologists previously suggested a Tibetan 'plateau' of more than 4km in elevation, nearly as high as today. However, the discovery of the ancient palm leaves show that the region was significantly lower than first thought. The elevation measurement was made by exploiting the unique cold sensitivity of palms combined with novel climate model simulations of ancient winter temperatures across a range of possible ancient landscapes. The research found that only a deep central valley with a floor at approximately 2km fringed north and south by high (more than 4.5 km) mountains provided the right conditions to allow palms to grow, particularly during the most cold-sensitive seedling stage of their life cycle. Professor Tao Su Xishuangbanna from the Tropical Botanical Garden at the Chinese Academy of Sciences, said: "We collected these palm fossils from Lunpola Basin in the summer of 2016.