Le karst haut alpin du Kanin (Alpes juliennes, Slovénie-Italie). Etat des connaissances et données récentes sur le fonctionnement actuel et l'évolution plio-quaternaire des structures karstiques

Abstract

The high-alpine Kanin karst (Julian Alps, Slovenia-Italy). State of knowledge and new data on present functioning and plioquaternary evolution of the karstic structures. Kanin is a high-alpine karst located in the Italo-slovenian Julian Alps. Its surface was elaborated by the quaternary glaciers and includes some inherited discreet tertiary morphological features. Recent dye tracing has shown that the structural setting permits water infiltrated in Italian catchments to contribute to Slovene springs. Hydrodynamic and physico-chemical water analyses show extremely quick transfers of water during snow melt or heavy storms ; these create spectacular overflows, such as the Boka spring which emerges as a 100 m high waterfall. The phreatic zone, linked to the impermeable dam of the Soca valley, does not significantly slow these transfers. Nevertheless, it contributes to the occurrence of low water levels during recession periods, giving highly mineralised water after long resident periods. The presence of very deep and developed karst systems is explained by the combination of advantageous factors : thick and jointed limestone, important height gradient, and considerable precipitation. Paleomagnetic dating in one of the largest systems (Crnelsko brezno) attributes some glacial sediments to the Lower Pleistocene period. Their configuration seems to show that this karst system is pre-quaternary.