天山玛纳斯河源鹿角湾冰川地貌与冰期序列

在鹿角湾冰川区40 km²的考察范围内,共发育了18个冰斗.按斗底高度的不同,可以将18个冰斗分成3个高度等级,分别代表了3次雪线高度不同的冰进.冰斗朝向以偏北为主,说明水热条件对冰斗发育是限制因素.18号冰斗和2号冰斗朝向偏南,说明其所代表的冰进阶段水热条件组合有利于冰川的长期存在,从而发育了大规模的向阳冰斗.鹿角湾冰川共发育了10道保存比较完整的冰碛垄,按冰碛垄表面特征和产出位置,结合测年资料,将10道冰碛垄划分为5套冰碛地层.对冰碛垄上所采冰碛土样品进行年代测试的结果是:冰碛丘陵上组地层属于小冰期沉积,较早的两次冰进结束时间为(680±60)a BP和(250±60)a BP;冰碛丘陵组地层属于新冰期沉积,3次冰进结束年代分别为:(4.2±0.4)ka BP,(2.9±0.3)ka BP,(1720±60)a BP;末次冰期晚期结束年代为1.1~1.2 ka BP.其它几次冰进阶段未能取得可信的测年数据.

Glacial Landforms and Glaciations at the Headwaters of the Manas River in the Tianshan Mountains

There are 18 cirques in the studied area (40 km²) of the Lujiaowan Glacier at the headwaters of the Manas River in the Tianshan Mountains.All these cirques can be recognized as three levels,showing that there were three times of glacier advancing of different scale.Most cirques face to north,showing that the heat-water conditions were disadvantageous for glacier developing.Cirques No.18 and No.2 face to south,which means there were good conditions for glacier developing for a long time at the periods of glacier advancing they took place. There are 10 well-conserved moraines can be recognized in the main valley,which can be divided into 5 stratum: upper moraine knap stratum,moraine knap stratum,lower moraine knap stratum,watershed stratum and forest level stratum.The upper moraine knap stratum is considered as a sediment in the Little Ice Age, and the forest level stratum is considered as a sediment in the oldest glacier advanced in the region.Judging from the morphology characteristics,the forest level stratum is considered as the deposit of the Reciprocal Third Glaciation or the Penultimate Glaciation. There were five times of glacier advancing at least in the region.The latest one was the Little Ice Age,including three phases of glacier advancing and shrinking.The two older phases were in about (1720±60) a BP and (250±60) a BP. The Neoglaciation included three times of ice advancing and shrinking,of which the first and the last one respectly occurred in (4.2±0.4) ka BP and (2.9±0.3) ka BP.The Last Glaciation included two times of ice advancing and shrinking,of which the last one occurred during 11~12 ka BP.The watershed suit and the forest level suit mean two times different glacier advancing.The watershed stratum may be deposited in the forepart of the Last Glaciation or in the Penultimate Glaciation.The forest level stratum may be deposited in the Penultimate Glaciation or the Reciprocal Third Glaciation.