喀喇昆仑山-西昆仑山地区湖泊演化

由于地质构造的控制,本区湖泊可分为三个湖泊带。本区湖泊几乎均为封闭湖泊,在湖盆中有众多的古湖岸线遗迹。由古湖岸线的分布推算高湖面时期的古湖泊范围为本区总面积的10.6%,为今日湖泊面积的3.06倍。根据地貌、第四纪沉积和¹⁴C 测年数据分析,最高湖面时期即最高古湖岸线所围限的古湖泊出现的时期为40000—20000aB.P.,大致与末次冰期间冰段相当。本区湖泊退缩十分强烈,喀喇昆仑山以北的湖泊退缩速度大于喀喇昆仑山以南。

EVOLUTION OF THE LAKES IN THE KARAKORUMWEST KUNLUN MOUNTAINS

The lakes of tht Karakorum-West Kunlun Mts.are mainly in the eastern part of the area（78°30′—82°30′E.32°40′—36°00′N） with an average height of about 5000m a.s.l.Some 51lakes （more than 1km² individually） with total area of about 2468 km² are in this area,inwhich the lake concentration （3.47%） is a bout 1.7 times as much as that of 2% over the wholeplateau.The majority of lakes in this area are closed interior lakes.As controlled by geo-logical structures the lake basins sited apparen（?）ly in three belts:the northern belt located at thesouthern side of Wtst Kunlun Mrs.;the middle belt located at the northern side of KarakorumMts.and the southern belt at the southern side of Karakorum Mts.Many ancient shore lines are well preserved on the lake basins in this area.Around Tian-shuihai lake the ancient shore lines are counted as many as 40.The highest shorelines is 60 mabove the present lake level of Tianshuihai lake.During the highest lake level epoch,the biggestancient Tianshuihai lake combined with ancient Aksayqin and formed a united big lake.Thisancient lake is 7.7 times in area as large as the present two lakes.Some 70 shorelines arefound surrounding the lake Longmu Co,the highest shoreline is 150—160 m above the presentlake level,the area of the biggest ancient Longmu Co lake is 4.7 times as large as that of presentlake.The ancient lake Bangong Co is 1.5 times in area as large as that of present lake BangongCo.During the highest lake level epoch the area of the ancient lakes took about 10.6% of allarea which is about 3.06 times as large as that at present.The features show that retreating oflakes appeared widely in this area but it went more rapidly in the north than in the southof Karakorum Mrs.Basing on the distribution of the highest shorelines,Quaternary sedimentation and the ra-diocarbon dating,it can be considered that the ancient lakes limited by the highest shorelinesin this area were formed during 40000—20000 a B.P.,as the age of highest lake level is moreconfirmed to be from 40000 to 25000 a B.P.according to the corrected ¹⁴C dates obtainedfrom natural profile at Tagutuqion to the east of the lake Bangong Co.In one word,all these features show that the retreats of interior lakes in the eastern partof Karakorum-West Kunlun Mts.are most viol nt on the Qinghai-Xizang Plateau since latePleistocene.This process is reasonably correlat d to the global climatic changings and the in-tensive uplift of the plateau.