Eocene paleoelevation of the Tuoyun Basin, northeastern Pamirs: Evidence from a lava-vesicle-based paleoaltimeter

Abstract

The arc-shape Pamir tectonic belt is located on the northwestern margin of the Tibetian plateau. At present, there are many different understandings on the history of the Pamir Plateau uplift, mainly on the time of uplift, which seriously affects the understanding of the global paleo-environmental changes since the Cenozoic. The method of reconstructing paleoelevation based on lava vesicles has improved in recent years, providing the means for establishing reliable constraints on the uplift time of the Pamir plateau. We studied Cenozoic vesicular basalt from the Tuoyun Basin in the northeastern margin of the Pamir tectonic belt. We used a lava-vesicle paleoaltimeter that measured vesicle volume at the tops and bottoms of two basalt layers, allowing the elevation of the Tuoyun Basin during the Eocene to be reconstructed according to the relationship between atmospheric pressure and altitude. Results show that the Tuoyun Basin had reached the elevation of > 2000 m at ca. 48 Ma, indicating that the influence of the Pamir tectonic belt on the Tianshan Mountains began during the Eocene. This new finding offers our contribution to better understand the impact the uplift of the Tibetian plateau on the Tianshan region and the environmental changes in central Asia during the Cenozoic.