Landscape change and its influence on human activities in Lhasa basin of central Tibetan plateau since the last deglacial

Abstract

Human activity and adaptation to the environmental changes on the Tibetan Plateau are under debate. Lhasa is the political and economic center of the Tibetan Autonomous Region, and was founded in 633 CE. The potential influence of changes in the landscape on the city's development remains unclear. In this paper, Optically Stimulated Luminescence and radiocarbon dating techniques were applied to determine the ages at which landforms have changed since the Last Glacial Maximum. Combining these results with archaeological evidence taken from two sites (Changguogougou and Qugong) in the Lhasa area, the relation between river migration and human adaptation was discussed. The results showed that the two terraces (T1 and T2) of the Lhasa River are fill and fill-cut terraces, and that these were formed after ∼0.9 ka and 0.08 cal ka BP, respectively. Land below an altitude of ∼3650 m above sea level was lower than the contemporary river level before ∼0.9 ka. With the down cutting of the Lhasa River, more land became available for habitation, and the flood risk to the city was also reduced. The sediments of the lower land around the Changguogou area appear to be composed of fluvial-lacustrine facies during the Last Glacial Maximum to Late Glacial period. Humans occupied the Changguogou area between ∼3.255 and 3.059 cal ka BP when there was weaker aeolian activity, and abandoned this area when aeolian activity increased.