Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla 666303, China.
University of Chinese Academy of Sciences, Beijing 100049, China.
Sci Adv. 2019 Mar 6;5(3):eaav2189. doi: 10.1126/sciadv.aav2189. eCollection 2019 Mar.
The Late Paleogene surface height and paleoenvironment for the core area of the Qinghai-Tibetan Plateau (QTP) remain critically unresolved. Here, we report the discovery of the youngest well-preserved fossil palm leaves from Tibet. They were recovered from the Late Paleogene (Chattian), ca. 25.5 ± 0.5 million years, paleolake sediments within the Lunpola Basin (32.033°N, 89.767°E), central QTP at a present elevation of 4655 m. The anatomy of palms renders them intrinsically susceptible to freezing, imposing upper bounds on their latitudinal and altitudinal distribution. Combined with model-determined paleoterrestrial lapse rates, this shows that a high plateau cannot have existed in the core of Tibet in the Paleogene. Instead, a deep paleovalley, whose floor was <2.3 km above mean sea level bounded by (>4 km) high mountain systems, formed a topographically highly varied landscape. This finding challenges prevailing views on tectonic processes, monsoon dynamics, and the evolution of Asian biodiversity.
青藏高原核心区晚古近纪的地表高程和古环境仍未得到解决。在这里，我们报告了在西藏发现的保存最完好的最年轻的化石棕榈叶。它们来自晚古近纪（渐新世），距今约 2550 万年，位于青藏高原中部伦坡拉盆地（32.033°N，89.767°E）的古湖泊沉积物中，目前海拔 4655 米。棕榈叶的解剖结构使它们容易受到冰冻的影响，从而对它们的纬度和海拔分布施加了上限。结合模型确定的古陆地坡度率，这表明在古近纪，青藏高原的核心地区不可能存在高原。相反，一个深古河谷形成了一个地形高度多变的景观，其谷底低于平均海平面 2.3 公里，被（超过 4 公里）高的山脉系统包围。这一发现挑战了关于构造过程、季风动态和亚洲生物多样性演化的主流观点。
