【摘要】 宽谷及宽谷阶地的形成与流域内的构造抬升活动密切相关。文中在考察阿尔金北缘断裂东段雁丹图与长草沟宽谷的基础上 ,结合古气候资料 ,探讨了晚更新世晚期以来两地河流阶地所反映的构造抬升。雁丹图自约 16 1kaBP以来发育了 3级堆积阶地 (T1,T2 与T3) ,并出露埋藏主要宽谷。 3级阶地面年龄分别约为 16 1ka ,12 8ka ,6 2ka ,反映了 3次构造抬升的存在 ,代表了 3次构造抬升发生的时间。雁丹图自约 16 1kaBP以来的构造抬升速率约为 4 8～ 4 5mm/a ;12 8～ 6 2kaBP间的抬升速率约 6 4mm/a ;6 2kaBP以来为 3 1mm/a。长草沟在 7kaBP以来有 4级阶地发育 (T3,T2 ,T′1与T1) ,均为堆积阶地 ,并出露埋藏宽谷。其中T3与T2 出露埋藏主要宽谷 ,T′1与T1出露埋藏次要宽谷。T3,T2与T′13级阶地的阶地面年龄分别约为 7ka ,3ka,2 5ka。 4级阶地反映 2次构造抬升 ,一次在约 7kaBP ,一次在 3kaBP左右。自 7 0kaBP以来长草沟的抬升速率约为 5 9mm/a ,在 7～ 3kaBP间约为 7 0mm/a ,3kaBP以来约为 4 7mm/a。更多还原

【Abstract】 Strath terrace is tectogenetic stream terrace.In equilibrium state,lateral erosion of the stream bevels bedrocks beneath the active channel,giving rise to widening of the channel and the formation of strath.Downcutting of the stream due to tectonic movement causes the rise of strath above the channel,resulting in strath terrace.Strath includes major strath and minor strath,and accordingly strath terrace includes major strath terrace and minor strath terrace.The existence of strath terrace may indicate that stream has once reached the equilibrium state,and that tectonic uplift has occurred.The investigation of strath terrace,therefore,may reconstruct the history of tectonic uplift of the studied area.Yandantu and Changcaogou are located at the middle segment of the Altun Northern Marginal Fault,where multistage strath terraces are well developed.Basing on field investigation of strath terraces and thermoluminescent(TL)dating of the ages of treads of terraces,and combining with the data of paleoclimate of Qinghai-Xizang Plateau,we dis-cuss the tectonic uplift since late Epipleistocene as reflected by strath terraces in these two areas.At Yandantu,three levels of stream terraces(T 1 ,T 2 and T 3 )have been developed since16ka BP,among which T 1 and T 3 are strath terraces,while T 2 is fill terrace.A buried major strath is exposed in the area as well.The ages of three treads are dated to be about16.1ka BP,12.8ka BP and6.2ka BP,re-spectively.The three terraces reflect three tectonic uplift events,while the three ages of treads represent the occurrence time of these events.The stream is still beveling the bedrock and widening channel at pre-sent,and modern strath is being generated.The uplift rate is4.8～4.5mm/yr since16.1ka BP in this area.From12.8ka BP to62ka BP,the uplift rate was6.4mm/yr,while since6.2ka BP till nowthe uplift rate is3.1mm/yr. At Changcaogou,four levels of stream terraces(T 1 ,T 2 ,T 3 and T′ 1 )have been developed since7ka BP.All of them are fill terraces,and there are buried straths under deposits of every terrace.The buried straths of T 3 and T 2 are major strath,and those of T′ 1 and T 1 are minor strath.The ages of treads of three terraces(T 3 ,T 2 and T 1 ′)are7ka BP,3ka BP and2.5ka BP,respectively.The four terraces reflect two uplift events induced by tectonic activities.One of them occurred in about7ka BP,and the other in3ka BP.The uplift rate is5.9mm/yr since7.0ka BP at Changcaogou.From7ka BP to3ka BP,the uplift rate was7.0mm/yr,and since3ka BP till now the uplift rate is4.7mm/a.更多还原