Case Studies from the Dinaric Karst of Slovenia

iver flow could be designated by the term ofcontact karst. The term grows familiar in Sloveniaand Croatia where the karst contacts noncarbonate rocks and specific relief forms andphenomena developed (Roglič 1957, Gams1973). The term is reasonable, because suchkarst essentially differs from the karst whichsurface and underground was formed by precipitationwater only. In the international karstologicalliterature these forms and phenomenaare usually named as karst influenced byallogenic inputs (Ford &Williams 2007).Contact karst develops where water flowsfrom fluvial relief onto karst. The distributionof contact karst is preconditioned to spatialdistribution of karstic and non-karstic rock orless karstified rocks like some dolomites. Becausehere is more water available dissolutionof limestone is faster than on other karst surfacewhere only precipitations shape the relief.Surface waters also transport and deposit sedimentsbefore they sink into sinks or ponorsand caves (Gams 1962). That is because theunderground channels are shaped by low oraverage water and can not transfer the highwaters, which causes short but regular floodingand precipitation of sediments in front ofponors. Corrosion is faster also because of thesediments are accelerating the corrosion beneaththem because of organic CO 2producedin sediment or soil. The results of these areoften widened bottoms of blind valleys beforesinks.Contact karst features are limited only tothe area influenced by sinking rivers. They aremostly depressions, most common are blindvalleys. These are valleys, which from nonkarst fluvial valley protrude some distance tokarst and end above the sinks. His relief hassome characteristics of fluvial relief, but thefeatures are karstic. The sinking into the karstis controlled by the gradient and the morphologyin the whole karst area between sink anda spring. If this is changing due to tectonicmovements, evolution of the caves also thecontact karst forms change. So we have often aset of evolutionary stages in the contact zone,reflecting the changes trough whole evolutionof karst (Mihevc 2007).We must differentiate between sinking riverson poljes and allogenic sinking rivers. Differenceis that the flooding in contact karst isbecause of surface inflow, while in the karstpoljes because of oscillation or rise of the levelof karst water.Areas of contact karst with developed reliefof blind valleys and similar border depressionsin Dinaric karst are in the inner side ofthe mountains where older noncarbonaterocks and Triassic dolomite are in contactwith limestone. On the Mediterranean sideof the karst main supply for allogenic sinkingrivers are Eocene flysch rocks. Best examplesare blind valleys in Matarsko podolje (Mihevc1993) and blind valleys in Istra peninsula.Largest sinking rivers are Reka with meandischarge 8 m 3 /s (max over 200 m 3 /s) thatsinks on the edge of Kras in Škocjanske jamecaves (Fig. 29). Large sinking rivers of contactkarst are also Pivka river (4 m 3 /s), Pazinska rekain Istra sinking in Foiba cave, Dobra which sinksnear Ogulin. Large sinking river is Zalomskareka that sinks in Biogradski ponor on Nevesinjskopolje with capacity over 110 m 3 /s.CavesCaves are one ob the most remarkablekarst features. We can find them from the highestkarst mountain to the lowest parts alongthe sea, and some of them are submerged belowthe recent sea level. Caves are active orrelict parts of the karst drainage system. Mostaccessible or known caves however are justsmall fractions of old relict cave systems. Activecaves are often flooded or obstructed withsediments. The cave distribution, morphologyand sediments give us information about evolutionof the whole karst.On the high karst mountains vertical shaftsand deep caves without horizontal passagesprevail. They were formed by vertical percolationof precipitations. The deepest caves are41