River Terrace Sequences In Upstream Of Lancang River And Its Relevance With Structural Uplifting

Located in southeast border of Qinghai-Tibet pleateau,mid-upstream of Lancang River has strong structrual movements and complicated landscapes so that river terraces are developed widely.As an important kind of landform surface,river terraces are regarded as a direct evidence to deduce geological movement widely,so it is feasible to analysis regional structural revolution and paleo-climate enviroments' transformation by sources of river terraces,which is also applicated in researching Qihai-Tibet pleateau uplifting.As it is affected by technological factors and poor transpotation condition in mid-up stream of Lancang River,lacking systemetic diving research,especially feasible data sources of terrace sequences and develop era causes neo-structrual movement tracing is confined.As for problems like these,we should perform field investigation of Changdu and Zuka period from Lancang River to recollate terrace sequences in Zuka,Changdu period from Lancang River.We use ESR dating method to detect the develop era of Changdu period and discuss its relation with structrual uplift in Changdu and then we can conclude as follows:(1)It develops third-layer pedestal terrace in Zuka period of Lancang River,the altitude of terrace are 25m,43-45m,55m and they all conserve binary deposited structure,it perfoms better in stone sizing and psephicity.(2)After recollacting 8 class river terrances in Changdu period from lancang river,most terraces are pedestal terraces except one class cumulated terrace.Altitude are 8m?25-52m?52.5-55m?53-72m?104m?140m?152m?183m respectively.(3)We eatablished river terrace era structure in Changdu period of Lancang River by ESR dating method and conclude that ESR era of 5,6,7,8 layer belongs to deep sea oxygenol isotopes MIS6?MIS10-8?MIS16.developing mode of Changdu terrace is "cumulate in ice period and sink in inter-ice period"and "Rotary cutting type during ice-inter ice period,cumulate in ice period.'based on structrual background.(4)Changdu terrace in Lancang River is effected strongly by uplifting of Qinghai-Tibet pleateau,so its terrace series' development has itimate relation with several uplifting events in Qinghai-Tibet pleateau,T8 of which is clearly effected by Kun-Huang movement during 1.2-0.6Ma,T4 of which is consequence of "Hegong movement "around 150ka.T5-T7 terraces are effected by structrual movement apparently,which has less datas in Qinghai-Tibet pleateau research but appears clearly in pleateau and its border area with relevant records.(5)Changdu river terraces from Lancang river at southeast of Tibet records several structrual uplifting since mid-Pleistocene,based on conconlusion of terrace dating and altitude we calculate ratio of regional uplifting is around 0.31?0.42mm/a,while it has relative low ratio in the last period of "Kunhuang ice period",only around 0.31 mm/a;Ratio of uplifting rises to 0.42mm/a gradually in 585-359ka;Afterwards,ratio of uplifting in pleateau descends to 0.30mm/a rapidly in just 20ka;Influenced by "Gonghe movement'around 150ka,structrural movement became intensly in pleateau and reached up to 0.36mm/a.However,uplifting ratio in southeast of Tibet is less than other region of pleateau and border region of pleateau.So we can't use under cut ratio to calculate mountain uplifting.