Study On Typical Drainage Basins Along Northeastern Tibetan Plateau And Its Tectonic Deformation

In recent years, fluvial geomorphology and its feedback to the tectonic deformation in active orogenic belt is becoming more and more popular to the geologists and geomorphologists all over the world; and the key study entry point is the carrier(modern landform), which has recorded the tectonic deformation and the climate changes in the geological time. meanwhile, spatial analysis and applications of the Digital Elevation Model(DEM) were introduced into the surface process and made the study transform from qualitative to semi- quantitative even quantitative. Such as the study of Hypsometric Integral in drainage basins, longitudinal river profiles and active rock uplift in different regions via bedrock channel longitudinal profiles.The Tibetan Plateau resulted from the collision between Indian and Asia continent and the northeast margin is becoming the youngest part of the Plateau. Making use of ArcGIS spatial analysis technology and MATLAB program, based on DEM data, we focused on four drainage systems and make them be the key entry points, discussing drainage geomorphic parameters’ feedback influence and its control on geological disasters. This paper draws the following conclusions:(1) By contrasting the various geomorphological parameters in the region, we find that all the geomorphological parameters have good consistency with the tectonic activity. For example, Danghe Nanhsan, which owns a higher intensity of tectonic activity, shows abnormal high level in the maps of land surface roughness, surface wavinesss, penetration depth and the dstruibution of HI values; This suggests that tectonic activity has a strong influence on the development of the modern surface topography and tectonic activity has a good consistency and correlation with the surface topography, that is, the areas which HI values are very low are consistent with the Quaternary fault basin, HI high values areas and the mountain ranges which strongly uplift in the late Pleistocene are consistent. We compared HI values with the vertical slip rates of all the faults in this study area, most slip rates of the faults match their HI values(the vertical slip rates of west, central and east segment of the Danghe Nanshan fault are 0.5±0.1mm/a、1.0±0.1mm/a and 0.9±0.1mm/a, and their HI values are 0.35-0.4、0.45-0.55 and 0.4-0.45), but Sanweishan fault has abnormal high HI values comparing with its vertical slip rate. Through the analysis of fault activities and the principle of Hypsometric Integral, we hold the opinion that the inherent defect of the Hypsometric Integral and the slip rate of Altun fault decreasing eastward influence the abnormal HI values in Sanweishan region. In all, we recognize that tectonic activity has strong influence on the development of geomorphology.(2) Stream networks of the Shu Le drainage basin extracted from the DEM data which based on GIS spatial analysis technology are graded into five levels using Strahler classification method. Four sub-catchments, numbered 1、2、3 and 4 were chosen for detailed analysis. The Hypsometric Integral curves, Hack profiles, SL index and average slope of the Shule drainage basin. Furthermore, the four sub-catchments were determined by GIS tools. The average elevation of the Shule drainage basin is very high, however, the slope the drainage basin is very low, the gentle slope occupies so large area proportion that the slope spectrum shows a unimodal pattern and a peak value is in low slope region(0-5°), so tectonic movement has a strong influence on the drainage basin. Under the intensive impact of the tectonic movement of the active fault and regional uplift, the hypsometric integral curve is sigmoid, revealing that the Shu Le drainage basin is in the mature stage. The Hack profile is on a convex, the longitude profile is best fitted by linear fitting and the abnormal data of the SL index of the Shu Le river has a good fit with the section through which the active fault traverse, that is the tectonic movement of the active fault has strongly influenced on the river’s SL index. It is worth noting that lithologic factors also impact the river geomorphology greatly in some sections.(3) Recent studies bring out that all the landscape factors(Hypsometric Integral、geomorphology entropy and river profiles) of east and west part of the Heihe basin exist obvious differences and the intensity of west part is stronger than the east. Comprehensive comparison and analysis show that the lithologic factors and precipitation conditions are less influencing for the geomorphic factors of the study area and the tectonic activity is the most important element for geomorphic evolution and development. At the same time, the strength of the tectonic activity also influence the geometrical characteristics of the river basins distribution.(4) Controlled by north Qilian Shan fault and Qilian-Haiyuan fault, the eastern margin of Qilian mountains have undergone strong tectonic deformation. The study shows it is the tectonic movement of the active fault but the lithologic factors and precipitation conditions that has strongly influenced on the regional geomorphic evolution; in addition, controlled by Huangcheng-Shuangta fault、Lenglongling fault and Lianhuaqiao fault, Gulang thrust nappe brings out high HI value, Hexibao-Sidaoshan fault, which lies on the east side of the Longshou hill, shows high HI value on its south side and relatively low HI value on its north side. In a word, all the macro geomorphologic factors indicate that the eastern margin of the Qilian Mountains, even Tibet Plateau has been extending northward, and his study provide the geomorphic evidence that the north Qilian Shan fault has extended into Hexi Corridor.(5) Based on SRTM-3 DEM, we made use of ArcGIS spatial analysis techniques and Matlab scripts to extract various geomorphic parameters in Bailongjiang drainage basin systematically, such as the macro landform information, seven fitting S-A graphics of four graded rivers. The results show that the convex fitting S-A graphics represents that the material output is bigger than the material input; on the contrary, the concave fitting S-A graphics represents that the material output is less than the material input; among which, the material input performs mountain uplift and the concrete manifestation of material output are landslide, debris flow disaster produced in emergency. In addition, mylonitization or half mylonitization strata distribution controlled by regional tectonic movement is the essential factors for geological disasters. Affected by the comprehensive factors above, we know that geological disasters usually occurs in the region that elevation changes rapidly, high relief amplitude and high slope distribution and different sub-basin topography caused by regional differences in uplift control the area where geological disasters occur frequently, that is, geological disasters occur frequently in the sub-basin which material output bigger than material input and the sub-basin which material input bigger than material output doesn’t show the geological disasters distribution points.