龙门山晚新生代地表剥蚀量的定量估算
Quantitative Estimation of Surface Denudation in Longmen Shan during Late Cenozoic

龙门山是青藏高原周边山脉中地形梯度变化最大的山脉．利用数字高程模型（ｄｉｇｉｔａｌｅｌｅｖａｔｉｏｎｍｏｄｅｌｓ，ＤＥＭ），采用三 维残余面法恢复龙门山晚新生代古残余面ＤＥＭ，并与现代地形面做差值运算，得到研究区域的剥蚀量地形，进而定量估算青 衣江、岷江、沱江和涪江主要水系流域晚新生代的地表剥蚀量．结果表明：龙门山晚新生代地表剥蚀总量为８０５００～ ９２８００ｋｍ３；岷江流域对龙门山地区剥蚀量贡献率约３３．９％ ～３７．１％，其次为涪江（３３．６％～３８．４％）、青衣江（２４．１％ ～ ３１．９％），沱江流域贡献率为０．４％～０．６％；类似２００８年“５·１２”汶川地震的次生灾害引发的地表快速剥蚀，是青藏高原东缘 龙门山造山带晚新生代地表剥蚀的主要原因．
Longmen Shan1ocated at the eastern margin of Tibetan Plateau represents the steepest gradient of the Tibetan Plateau edges. To assess thelarge-scale denudation volume inLongmen Shan, Late Cenozoic, surface denudation is quantitatively calculated a1ong sev- era1 large drainage basins such as Qingyijiang, Minjiang, Tuojiang, and Fujiang rivers by using digita1 elevation models(DEM) data, and residua1 surface methodwith paleo-residua1 surface DEMminus modern surface topography in this study. It is found that theLate Cenozoic denudation volume of upper reaches inLongmen Shan drainage basin is between80500 and92 800krn3. MinjiangRi 田ver has thelargest contribution ratio to denudation inLongmen Shan(33. 9%-37. 1%) , fo11owed by Fujiang(33. 6%-38. 4%) and Qingyi- jia昭 Hvers(24. 1%-31. 9%) , and TuojiangRi Hver hasminimum contribution(0. 4%-0. 6%). A rapid erosiona1 remova1 from the Longmen Shan by repeated great seismic eventslike the Wenchuanearthquake onMay12th, 2008, may be a main reason of the surface erosion inLate CenozoicLongmen Shan a1ong theeastern margin of Tibetan Plateau