Geoheritage values of the Dong Van Karst Plateau Geopark: A quantitative geomorphological and topographic analysis

The main purpose of this study is to analyse the geomorphological charactertistics of the Dong Van Karst Plateau Geopark (DVKPG) in the Ha Giang province of Vietnam. A digital elevation model (DEM) was generated using SPOT5 imagery and elevation and slope maps were then extracted from the DEM. A geological map at the scale of 1:200,000 was constructed and used for analyzing and visualizing the carbonate rock in three dimensions. The results show that there are two types of topographic development in the study area. The first, formed by tectonic movement and affected by major faults, is distributed in a NW-SE direction. The second was formed by exogenous geomorphological processes and influenced by both major and faults. It is distributed mainly in a NE-SW direction. Geological analysis indicates that ten stratigraphic formations crop out in the study area but only six of these have correlations with karst landscapes. Carbonate rocks are mainly distributed in the Dong Van district. They cover an area of 329.7 km 2 (71.7% of the entire district and 36.5% of study area). In constrast, there is few carbonate rocks in the Quan Ba district. In the case of slope, the slope angels from 15-30° cover about 53.5% of the study area. There are 1261 karst sinkholes in the study area with an average density of 1.4 sinkholes per km 2 .