The Geomorphological Characteristics And Evolution In The Panlong River And Lujiang River Basin

The karst geomorphology evolution in the Panlong River-Lujiang River Basin on the southeastern margin of the Qinghai-Tibet Plateau has a unique spatiotemporal coupling process,which intensively reflects the spatial differentiation process of the karst geomorphology under the background of the transition from the ancient planation plane to the giant slope topography pattern in the region.It is an important area to study the dynamic mechanism of spatial differe ntiation of karst geomorphology.The evolution of the geomorphology and its dynamic mechanism are complex processes with multiple temporal and spatial scales.Combining the digital terrain analysis of the geographic information system with the Davis geomorphology cycle theory,the Skovich depression cycle theory,and the Stralher area-elevation method,exploring the differentiation law of karst geomorphology under the background of the transition from the ancient planation plane to the giant slope terrain pattern and dynamic mechanism.The geomorphological differentiation of the Panlong River-Lujiang River Basin is the result of the structural dynamics and environmental changes on the altitude gradient caused by the uplift of the Qinghai-Tibet Plateau,and the watershed confluence,erosion and dissolution brought about by the development of the Panlong River-Lujiang River system.The cascaded slopes formed by the uplift of the plateau laid the foundation for the development of differential karst landforms in the basin.From the outlet of the basin to the source,they are accumulation and flattening plains,tectonic eroded granite mid-mountains,slope peaks and valleys,lysogenic gentle hills and fault depression Basins and structures eroded the lysogenic sub-alpine.Geomorphological indicators such as elevation,slope,undulation,and integral value in each area have mutual support for the consistency of topographic structure characteristics.The erosion and dissolution power from downstream to upstream first strengthened,then weaken ed and then strengthened,reflecting the The complete evolution stage of Davis's theory of geomorphology cycle in the process of leveling-uplifting-leveling.The analysis of the area-elevation analysis value of the multi-scale fusion of the basin as a whole,the upper,middle and lower reaches of the karst positive and negative topography depicts that the development and evolution of the Panlong River-Hujiang River Basin has undergone a rejuvenation process fro mold age to late adulthood,and is controlled by the watershed The 0.89‰ slope in the lower reaches descends to a large regional stepped terrain with a slope of 46 to 49‰ in the middle and lower reaches.The disintegration of the initial paleo-leveled karst landform is the basic process of the rejuvenation of the old-age landform;The spatial heterogeneity results in the particularity of the integrated values of the upper,middle and lower reaches of the geomorphic unit and the internal depressions,but the integrated value as a whole reveals the control mechanism of hydraulic slope and karst hydrogeological pattern on the development and evolution of the watershed geomorphology,reflecting the time and space of the factors affecting the evolution of the geomorphology.The process of scale fusion,the rapid uplift of the Qinghai-Tibet Plateau leads to the transformation of the terrain from the original ancient planation plane to the giant slope pattern,forming a step surface-slope-accumulation solitary hill lysogen,and the development of the river system makes the river sections The hydraulic connection is enhanced,and the dynamic environment on the altitude gradient and the dynamics of water erosion and dissolution are changed,which brings about the north-south and east-west differentiation of the landform.The comparison of the depression integral value and the DEM integral value corresponding to the upper,middle and lower reaches shows that when the depre ssion integral value is greater than the DEDM integral value,it indicates that the landform is developing in the direction of youth with increasing undulation,and when the depression integral value is smaller than the DEM integral value,it means that the landform is moving towards a decreasing undulation.The development of the flat erosion process is an important manifestation of the ev olution process of the Skovic depression,which provides a theoretical basis for taking the integral value of the depression as an important indicator of the dynamics of the evolution of the karst basin.Therefore,the Panlong River-Lujiang River Basin is a typical karst landform development and evolution under the fusion of plateau uplift and watershed hydrodynamics.The simultaneous heter ogeneous landform evolution from the source of the river to the drainage basin and the valley to the watershed on both sides is its important feature,which supplements the previous Human understanding of the heterogeneous evolution process of karst geomorphology at the same time lays an important foundation for exploring new karst geomorphology evolution models.