Holocene variations of the Yanzigou Glacier (Gongga Shan Massif, Da Xueshan, China)

Abstract

Extending from the Sichuan basin to the Tibetan Plateau in the Da Xueshan Mountains, the Gongga Shan is the highest massif (7514 m) in China east of the Himalaya and also one of the principal glaciated areas (255 km²) controlled by a monsoon climate. Geomorphological and historical research was carried out on the Yanzigou Glacier, which is located on the eastern slope and is one of the longest ice bodies on the massif. The objective of this research was to reconstruct Holocene fluctuations. Many end and lateral moraines were identified, some of which are completely covered with vegetation, while others are only partially covered with grass. The moraines were attributed to Little Ice Age advances and to 20%century fluctuations of the glaciers, respectively. Many layers of organic material (wood, soil, peat) were observed in the highly eroded inner wall of a right lateral moraine at about 3900 m a.s.l., consisting of a complex of superposed debris units. The radiocarbon dating of samples indicated at least six periods of glacier expansion prior to the Little Ice Age, between 4000 years BP to 700 years BP, as well as two glacier advances during the Little Ice Age. For the past 100 years, the Yanzigou Glacier has been in a phase of retreat (for a total of about 4 km), except for a short period of stability in the early 1980s. At the point of the glacier’s maximum extension in the Little Ice Age, the equilibrium line altitude was situated at about 4920 m, 180 m below the current one.