Palm fossils reveal new topography of Tibet
doi:10.1038/nindia.2019.28 Published online 6 March 2019
Newly discovered fossil palm leaves challenge the concept of a “proto-Tibetan Plateau”, a term that suggests that the central part of Tibet was flat 35-40 million years ago1.
The fossils bear testimony to a large valley system with a floor less than 2.3 kilometres above mean sea level. Such a valley existed in central Tibet as late as 25 million years ago.
It is known how the collision between the Indian and Eurasian plates shaped the topography of southern Asia, resulting in changes in regional and global climate. However, the topographic evolution and paleoclimate history of the Tibetan Plateau before and soon after the collision are very poorly understood.
An international research team, including a scientist from the Birbal Sahni Institute of Palaeosciences in Lucknow, India, discovered the fossil palm leaves in paleo-lake sediments within the Lunpola Basin in the central Tibetan Plateau. The fossil palm leaves displayed prominent spine-like structures at the base of the leaf blades that are different from any other previously reported palm fossils.
After consulting the literature and herbaria, the researchers placed the fossil palm in the genus Sabalites and named it Sabalites tibetensis.
Combining paleotemperatures at sea-level with climate model-generated local terrestrial thermal paleolapse rates for a range of topographic scenarios, they found that the central valley with a floor at about 2.3 kilometres was surrounded by high mountains in the north and south. It provided the right conditions to allow palms to grow, particularly during the most cold-sensitive seedling stage of their life cycle.
1. Su, T. et al. No high Tibetan Plateau until the Neogene. Sci. Adv. (2019) doi: 10.1126/sciadv.aav2189