Study On Tectonic Geomorphology And Drainage System Of The Longmen Mountain Area

The Longmen mountain area is located at the border between Tibetan plateau and SichuanBasin,and is the boundary strip of geology, geomorphology and climate in the Midwest of China.The Longmen mountain region is undergoing a significant landform deformation and now thegeological processes remains active. Because its late formation, the geological phenomenon ofthe mountain remains clear. The landform and drainage system, which can record the pattern oftectonic activity, is sensitive to the neotectonic. Therefore, the study on the landform anddrainage system can provide evidence of the uplift process of eastern Tibetan Plateau.Combined with the method of traditional geological analysis and SRTM-DEM date, thispaper analyses and studies the studied area. Firstly, the author arranges and summarizes theneotectonics of the main faults of the studied area. The modern tectonic stress field of the studiedarea has NWW-SEE pressing feature, which has the accordance of the neotectonics of thestudied area. Research on the surface rupture of Wenchuan earthquake shows that the LongmenMountain faults zone has the feature of strike-slip, thrust, and segmentation. Considered theterrain of the fracture belt and the feature of neotectonics, we presume that the earthquakeactivities are likely to have important impact on the Longmen Mountain uplift.With the help of the software of ArcGIS9.2 and the DEM data, the author analyses the spaceand extracts the geomorphic parameters of Longmen mountain area, and analyses the feature ofthe terrain such as the summit level, mean elevation, base level, average slope and local relief.Research shows that the middle south section of Longmen mountain tectonic belt and Minmountain uplift are higher slope and relief, which together build up the typical escarpment, andthe main faults control landform and physiognomy. In contrast, the north section of LongmenMountain does not form boundary of eastern Tibetan plateau. The terrain of the studied area hasthe feature of step, which is mainly dominated by the erosion of river, and the tectonic beltdevelops deep valley and channel of rock type.By employing hydrological analysis of ArcGIS9.2, the system extracts the drainagegeomorphic parameters of the studied area, and discusses the structural implication of the Min river and Fu river drainage system. The results shows that the asymmetry of the two basins iscaused by the deviation of the uplift of the Min Mountain block, which itself is also imbalanced.Different activeties of Minjiang fault, Huya fault and the faults felt of the middle south section ofLongmen Mountain clearly affect the two basins, while the north section of Longmen Mountainis not clear.Compared with the Min river basin, the Fu river basin develops more mature. Theriver system of the middle section of Longmen Mountain was controlled thrust and uplift, whilestrike-slip affects the drainage evolution in north section of Longmen Mountain.