7. Epikarst with Grikes: Tropical Karren of Bemaraha Type

Tropical karren were classified, among them, the development of giant grikes and within these the development of tropical karren of Bemaraha type was interpreted. For this reason, the landscape of tropical karren (the distribution of certain types of grikes on tropical karren), their elevation relative to the base level of erosion and the karstwater table, their distance from sea shores and in the area of some, the temporal distribution of precipitation were studied. Tropical karren may be karren with or without grikes. At tropical karren with grikes, the Bemaraha type (the karstwater table is close to the surface) and Ankarana type (the karstwater table is deeper relative to the surface) are distinguished. It can be established that large, complex grikes that are specific of Bemaraha type occur on karsts whose relative height is low relative to their base level of erosion. As a result of this fact and the fluctuation of karstwater table, the karstwater table is close to the surface and mostly these karsts are close to shores. Due to the above-mentioned characteristics, the wet part of the epikarst is absent on these karsts or it is partially developed (if it has already been inactive, or transformed or secondarily developing). According to its environment, tropical karren of Bemaraha type may be of marine environment (its karstwater is affected by the sea level) and of terrestrial environment (its karstwater is not affected by the sea). In the development of the karst areas of tropical karren of Bemaraha type, three stages were distinguished (the stage preceding coalescence, the coalescence stage, and the denudation stage).