On concepts and methods for the estimation of dissolutional denudation rates in karst areas

The paper discusses methods and principles used to estimate dissolutional denudation rates in karst areas. Surface lowering can be measured directly by micro erosion meters or calculated from the mass loss in rock tablets exposed to dissolution in different environments. Indirect approaches are based on the measurements of solute load leaving the catchment area, geomorphological investigations and methods of cosmogenic nuclides, particularly 36Cl. Calculations based on the solute load measurements generally give higher denudation rates than direct measurements on the surface of limestone terrains. This can be explained by the fact that only about 30% of water's dissolution potential is used on the exposed surfaces and the rest is done deeper in the fracture system. The role of endokarst dissolution is demonstrated with a denudation model of rock column where dissolution rate depends solely on the distance from the surface. The denudation rates of a uniform rock column approach maximal when the thickness of the removed rock is about twice an e-folding length for the dissolution rates. The model also gives possible mechanisms for differential denudation in regions with different infiltration intensity and fracture density.