Case Studies from the Dinaric Karst of Slovenia

ploration and for the visitors started in 1884.Cave exploration and construction of the pathwayswere done by cavers of DÖAV from Trieste.The most important explorer was AntonHanke. In 1891 they reached the final sump inthe cave.Because of their extraordinary significancefor the world’s natural heritage, in 1986 theŠkocjanske jame were included in UNESCO’sWorld Heritage List. The Republic of Sloveniapledged to ensure the protection of theŠkocjanske jame area and therefore adoptedthe Škocjanske jame Regional Park Act. TheŠkocjan Caves were entered also on the RamsarList of Wetlands of International Importancein 1999. Together with the underground RekaRiver, they represent one of the longest karstunderground wetlands in Europe.Križna jamaKrižna jama is large river cave 8,273 m long.It is situated in the area between Loško, Bloškoand Cerkniško poljes. The relief above the caveis characterized by conical hills and closed depressions,dolines, uvalas and small, polje-likelevelled surfaces. The entrance of the cave islocated in an elongated karst depression to theeast of Križna gora (856 m a.s.l.).The cave is developed in the light greymicritic Liass/Dogger limestones, with lensesof dolomite (Gospodarič 1974; Buser, Grad &Pleničar 1967). The cave was formed in ratherstable conditions between the Cerkniškoand Loško polje, as indicated by the mostlyepiphreatic conditions of passage evolution.A small river with autogenic catchment areaflows in the cave and continues through at least124 m deep terminal sump towards the westinto the cave, Križna jama II, and to springs atCerkniško polje. The active water passages arelocated at about 610 m a.s.l. The older passagesare slightly higher, between 620 and640 m a.s.l. Remains of fluvial sediments arepreserved throughout the entire cave, indicatingthat it was filled by more sediments in thepast (Gospodarič 1974). The remains of Ursusspelaeus in clay inter-beds among flowstonesheets are important in the Medvedji rov. Theywere studied by Hochstetter (1881), Rabeder& Withalm (2001), Pohar et al. (2002) and theothers. The most detailed study of fluvial sedimentswas done by Gospodarič (1974), whoconcluded that the cave was much more filledby sediment in the past and less open than it isat the present time.Unroofed Caves and Surface DenudationOn several places on Kras allogenic sediments,quartz sands and pebbles can be foundon the surface. Their appearance was explainedas remains fluvial deposits of surfacerivers. These sediments were the basis for thepresumption of pre-karstification period andseveral karst forms were described as remainsfrom that period (Radinja 1969; Melik 1962).New interpretation of these localities togetherwith geomorphologic and sedimentary studiesreveal (Mihevc 1996; Mihevc & Zupan Hajna1996; Mihevc 2001) that these are the cavesediments exposed to the surface because thedenudation removed the rock above the caves.The appearance of old unroofed caves andtheir fills resulted from denudation, erosionand chemical dissolution of limestone abovethe cavities. Fills exposed on the present surfaceinclude speleothems and cave fluvial deposits.The ancient directions of flow, differentcatchment areas of sinking rivers and differentorganisation of the ancient undergrounddrainage were reconstructed from several unroofedcaves opened during highway construc-63