Case Studies from the Dinaric Karst of Slovenia

smaller than the higher ones. The river bed iscomposed mostly of gravels derived from theEocene flysch. The mean annual discharge ofthe river is 5.2 m 3 /s. The water level can rise10 m during floods.Cave fill was originally expected not tobe older than Middle Quaternary (i.e. about0.4 Ma). Pleistocene large mammal fauna suchas hippopotamus, cave lion and cave bear,were found here (Rakovec 1954) as well as Paleolithicstone tools from the last glacial (Brodar1969). Later numerical dating (Th/U andESR) indicated ages older than 0.53 ka. Newpalaeomagnetic data from selected sedimentaryprofiles within the cave system detectednormal polarization in prevalent amount ofstudy profiles. Reverse polarized magnetozones,interpreted mostly as short-livedexcursions of magnetic field, were detectedonly in places. Therefore we (Zupan Hajna etal. 2008a, b) interpreted most of studied sedimentsas younger than 0.78 Ma, belonging todifferent depositional phases within the Brunheschron. Palaeomagnetic properties on twoprofiles in the caves intersected by artificialtunnel between Postojnska jama and Črnajama with reverse polarized magnetozones,and sediments in Zguba jama, can indicate agedeeply below 0.78 Ma.The cave system shows long evolution governedby the function of the Planinsko poljein the relation to the evolution of resurgencearea in Ljubljana Moor farther on the east. Thegeneral stabilization of the hydrological systemwith low hydraulic head led to evolutionof caves in epiphreatic and paragenetic conditionsfor a long time-span. Individual cavesegments or passages were fully filled andexhumed several times during the cave evolution.The alternation of depositional and erosionphases may be connected with changingconditions within the cave system, functionsof the resurgence area, collapses, climaticchanges, tectonic movements and the intrinsicmechanisms of the contact karst.Škocjanske jameŠkocjanske jame are 5.8 km long cave. TheReka River enters the cave at an altitude of317 m; in the Martelova dvorana room, it is214 m above sea level (i.e. 103 m lower). TheReka can also sink before it enters the cave.Floods usually reach up to 30 m, higher floodsare common too, and the largest known floodin the 19 th century raised the water table levelfor 132 m. Caves are developed in a contactarea of Cretaceous thick-bedded rudistic limestoneand Palaeocene thin-bedded dark limestone.The cave is composed of phreatic tunnels,and gravitational or paragenetic reshapedgalleries. The proto-channels developedin phreatic conditions along tectonisedbedding-planes. The water flow demanded ahigh degree of phreatic rising and falling betweenindividual bedding-planes which, in thearea of the chambers Svetinova dvorana andMüllerjeva dvorana, is approximately 175 m.Large quantities of water could flow throughall these tunnels, but meanwhile, rubble wastransported through water table caves abovethem. Such a cave is the unroofed cave in Lipovedoline at an altitude of around 450 m.A long period followed when the piezometricwater table was 340-300 m above sea leveland the gradient was in a southwest direction.In it Reka formed new or adopted old passagesby paragenesis and bypassing. These large gallerieswere Mahorčičeva and Mariničeva jama,Tominčeva jama, Schmidlova dvorana in Tihajama. The largest chambers are Martelovadvorana, with a volume of 2,100,000 m 3 , andŠumeča jama (870,000 m 3 ). Some of big chamberscollapsed forming the big collapse dolineslike Velika and Mala dolina.In the further development of Škocjanskejame, potent entrenchment prevailed. Cuttingoccurred in inner parts of the cave, in Hankejevchannel for about 80 m, much less, about10 m, in the eastern, entrance part of the cave.The first paths in the cave area were madein 1823, but the construction of paths for ex-62