Geomorphology and speleogenesis of the karst system of Venado caves, Costa Rica

Abstract

The karst of Venado in San Carlos is hosted in the Miocene limestones of the Venado formation, and comprises cave systems, dolines, sinkholes, karst springs and underground rivers. Limestones are partially covered by Quaternary volcanic rocks (e.g. lavas, lahars, tephras) and landslide deposits. The zone has an important structural domain, influenced by the Venado Transtensive System, which is dominated by dextral faults with NW traces. The Venado karst cave system consists of three main caves: Menonitas, Higuera and Gabinarraca, in which a total of 4925 m of passages have been mapped. The Gabinarraca cave is the best known, since it has been used for tourism for over two decades. The morphology of the cave passages suggests an important structural domain, as well as a significant contribution of sediments during speleogenesis, which is evidenced in paragenetic passages, alluvial notches, passages filled with sediments and typical patterns of caves formed by floods. The hydrological connection of the three main caves was confirmed by tracers, being the largest known cave system in Costa Rica. Based on tracer tests and chemical analyzes of water, it is suggested that the water has a residence time of less than one day in the aquifer.