Research On Late Cenozoic Surface Denudation And Isostatic Rebound In Eastern Kunlun Mountains Based On DEM

The study area is located in the Eastern Kunlun Orogenic Belt of northernQinghai-Tibet plateau, an average elevation of about4800m. The north of the mainridge of the Kunlun Mountains has strong cutting and steep terrain, it’s a deep cuthigh mountains. The southern slope of the Kunlun Mountains has shallow cutting,with relatively gentle relief, and representing gentle hummocky high mountainslandscape. The maximal topographic relief is over4000m. According to the upperlimit of age the main surface of the Qinghai-Tibet Plateau formed, it is speculated thatthe rapid uplift of Eastern Kunlun might initiate since3.6Ma, and coincide withdenudation began.By used high resolution digital elevation model data, this thesis has assessed andanalyzed the regional denudation volume and the Isostatic rebound associated withdenudation in the mainly drainage basins of the study area in Eastern KunlunMountains in late Cenozoic, and I get the following results.(1)The optimum statisticalunit of the study area in Eastern Kunlun is600m*600m.(2)The regional denudationof the main drainage basins in late Cenozoic is quantitatively estimated by usingswath profile method and planation method, and the planation method is moreaccurate and applicable to estimation for the regional denudation volume than swathprofile method. The denudation volume of upper reaches since3.6Ma in theNalingguole River, Wutumeiren River and Golmud River is between19067.56km3to25621.09km3, and the denudation rate is about0.1168-0.1570mm/a. It is inferredthat the Nalingguole River has the largest contribution ratio to the denudation inEastern Kunlun area, the ratio is about44.99%-50.71%. The maximal denudedthickness is over2000m in the study area, and the thickness on both sides along theriver valley area is more than1000m. The thickness of the middle and lower reachesarea of Golmud River and Nalingguole River is near2000m, the larger denudedthickness areas of Wutumeiren River are located in the piedmont zone, and thethickness gradually decreases extends to the interior of the plateau and piedmontalluvial plain area.(3)Due to the large amount of denudation, the Eastern Kunlun Mountains did not reduce the elevation, but continually uplift, thus, part of the LateCenozoic uplift of Eastern Kunlun Mountains is related to the theory about Isostaticrebound associated with denudation. The3-D elastic flexural modeling is used forquantitatively estimating Isostatic rebound due to the denudation of the mainlydrainage basins in the Eastern Kunlun Mountains region. The recovery result showsthat the overall elevation of the study area is more than4000m, and terrain isrelatively flat, indicating that the high altitude terrain of Qinghai-Tibet plateau hadbeen formed before3.6Ma. Due to the large amount of denudation volume,Nalingguole River drainage has largest flexural deflection, is about350-500m, partsof it is up to450-500m. The flexural deflection along the margin of Tibetan plateau tothe high altitude region in Eastern Kunlun Mountains is larger than other region, fromthe high altitude mountains to the interior of the plateau and the piedmont alluvialplain, the amount of flexural deflection gradually declines; the flexural deflection ofWutumeiren River is about300-400m, and Golmud River has the minimal flexuraldeflection, is about300m. I suggest that the elevation of Eastern Kunlun Mountainsis the combined action result of Tibetan plateau overall uplift and Isostatic rebound ofcrust.(4)Finally, tectonic uplift of Eastern Kunlun Mountains is considered as themain reason for the uplift of Late Cenozoic, while the contribution to the total upliftof denudation and Isostatic rebound accounts for only about one-tenth.