Research on hydrogeomorphologic characteristics and evolution of the watershed on the Gaopo karst tableland in Huaxi of Guizhou
In order to explore the hydrogeomorphologic characteristics and formation mechanism of the watershed on the Gaopo karst tableland in Huaxi,Guizhou,this study investigates the spatial distribution of geological structure,lithology and geomorphology,in conjunction with the hydrological characteristics of the study area. It employs the theory of karst hydrogeomorphology to discuss the development of these characteristics. The results indicate:(1) The karst landforms of the Gaopo karst tableland,including poljes,edge poljes,peak-forest valleys,island peak clusters and karst caves,are well developed and exhibit layered structural characteristics. (2) The peak-forest valley is mainly developed in the watershed area between the Dumu river and the Baijin river. (3) The landform transitions from the watershed to the drainage base,displaying a spatial distribution pattern of peak-forest valley→peak-cluster depression→valley (or isolated peak).The analysis shows that fractures,joints and faults are the dominant factors controlling the northeastward and southeastward trend of the valley in the study area. Spatial distributions of carbonate rocks and non-carbonate strata play a certain decisive role in karst geomorphology. On the Gaopo karst tableland in Huaxi,there is an erosion base at Grade-5 in the valley and at the transition end of the broad anticline,but not in the watershed area. This phenomenon is caused by the fact that the crust began to rise again before the river tractive erosion in a certain period spread to the study area. In the broad anticline area,the tractive erosion path of the previous period spread to the center area,so only a Grade-4 erosion base was formed in the study area. Based on the layered geomorphic structure,it can be seen that from the center to the edge of the tableland and then to the valley,there is a turning point in the erosion base at the edge of tableland. In addition,the erosion base of each grade from the anticlinal transition end to the anticlinal center (from the edge to the center of tableland) is relatively stable with small hydraulic gradients,but the hydraulic gradients in erosion bases from the transition end to the synclinal valley are much larger than those on the anticline. Therefore,in the process of drainage from the center to the edge of tableland and then to the valley,there is also a turning point for the groundwater level as well as the surface water level of Gaopo karst tableland at its edge. As a result,the flowing rates of both the surface runoff and groundwater runoff on the box anticlinal karst tableland are slow,or the runoffs are transformed into karst lakes and pools inside the box anticlinal karst tableland,whose side erosion is strong,forming karst landforms of peak-forest plain,peak-forest valley,etc. However,with the gradual strengthening of traceable erosion,the turning point also gradually retreated to the center of the tableland,and finally the groundwater level of the tableland disappeared. With the retreat of the turning point,the groundwater level gradually decreased,the saturation zone gradually thickened,and the movement of surface water and groundwater shifted from the horizontal to the vertical. As a result,a large number of depressions,funnels,sinkholes and vertical shafts were developed on the surface.Therefore,it is believed that the formation and evolution of karst geomorphology in the watershed area of the Gaopo karst tableland in Huaxi are closely linked to the development of platform hydrological structure. Throughout geological history,the platform water system has been affected by the tractive erosion caused by surrounding rivers,leading to the disintegration of the surface hydrological network from the edges toward the center of the platform. In this process,the karst geomorphology of the Gaopo karst tableland experienced four stages:stone clint-lake,peak-cluster depression,peak-forest valley and the degradation and extinction of platform geomorphology system.
万方数据
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