3.2ka BP以来念青唐古拉山东部则普冰川波动与环境变化

Variation of Zepu Glacier and Environmental Change in the Eastern Nyainqêntanglha Range since 3.2 ka BP

基于野外考察和14C年代测定, 确定了3 2 ka BP以来念青唐古拉山东部则普冰川的冰进序列.新冰期冰进可明显分为3次: 即大拿[14C(3 242±101)a BP]、大拿顶[14C(1 920±110)^(1 540±85)aBP]和白同[14C(1 056±115)a BP]冰进.新冰期盛时, 则普冰川比现代长 6 9 km, 面积大 17 10 km2,雪线降低约157 m, 温度降低1 0~1 9 ℃. 小冰期可分出2次: 即15世纪或16世纪[14C(580±130)aBP]和19世纪[14C(197±80)a BP, (190±80)a BP]冰进. 小冰期盛时, 则普冰川比现代长 2 0 km, 面积大11 16 km2, 雪线降低约100 m, 温度降低0 65~1 23 ℃. 现代则普冰川, 冰面表碛特别发育, 其厚度亦很大, 冰舌末端退缩难以辨认. 但冰川减薄很强烈, 边缘两侧形成 2~3 道现代侧碛, 并高出现代冰面20~30 m. 对埋藏腐殖质土壤层和木炭碎屑经14C年代测定, 结果表明在(720±210)^(2 010±120)a BP间, 波堆藏布流域存在砍伐森林、开垦田地和放牧的人类活动.

The advance sequence of the Zepu Glacier in the Bodoi Zangbo watershed in the Nyainqê ntanglha Range during the last 3^2 ka are revealed by field investigation and {{}^(14)C} dating data. Three advances of the glacier in the Neoglaciation can be obviously distinguished. They are Dana Glacial Advance [{{}^(14)C} ({3 242}±101) a BP], Danading Glacial Advance [corresponding to Ruoguo Glacial Advance, [{{}^(14)C}({1 920}±110)^({1 540}±85)a BP] and Baitong Glacial Advance [{{}^(14)C}({1 056}±115)a BP]. In the Dana glacial advance, the Zepu Glacier was 6^9 km longer, its area was 17^10 km^(2) larger, and its snowline was 157^0 m lower than those at present, and air temperature was 1^0~1^9 ℃ lower than that at present. Two advances of the glacier in the Little Ice Age can be distinguished. They occurred in the 15th or 16th century [{{}^(14)C} (580±130)a BP] and the 19th century [({{}^(14)C} {197 80}~{190 80} a BP)]. In the glacial advance in the Little Ice Age, the Zepu Glacier was 2^0 km longer, its area was 11^16 km^(2 )larger, and its snowline was about 100^0 m lower than those at present, and air temperature was 0^65~1^23 ℃ lower than that at present. Superglacial till develops particularly on the surface of the glacier. The glacier is still very thick, and the shrinkage of the glacier tongue is not so obvious. However, the glacier is violently thinning, and several modern flank moraines form in both sides. The {{}^(14)C} dating data of charcoal oddments and humus buried in earth reveal that there were some human activities including deforestation, land reclamation and grazing in the Bodoi Zangbo watershed during the period from {2 000} to 700 a BP.