Case Studies from the Dinaric Karst of Slovenia

Fig. 31: The oldest caves are found on the surface where they are incorporatedinto the karst surface. Example of unroofed cave by Povir at Kras plateu, Slovenia(photo: J. Hajna).water level, dry and blind valleys and cavesthat are now exposed to the surface due tokarst denudation. This tells us about the genesisof the landscape trough different phasesbut not the age of a karst features itself.Measurements show, that denudation islowering surface of karst with rate between30-50 m/Ma (Gams 1963; Gabrovšek 2009). Ifwe consider, that the then we understand thatmost of the surface karst features can not beolder than maybe 3-6 Ma.The oldest elements in karstare probably the caves thatformed deep below the surfaceand are now exposedas unroofed caves (Mihevc1996, 1998, 2001; Fig. 31).Real datation of karst ispossible only from the sedimentsthat were depositedin karst features, caves orkarst depressions. Differentmethods are used and theycan date only the time of thesedimentation.Datation of flowstoneusing different U/Th methodswe can date only about500,000 years old sediments,that is the limit ofthe method. Paleomagneticanalyses can give us paleomagneticrecord in sediments,but method is relative,so the data has to becalibrated by some othermethod, like palaeontology(Zupan et. al. 2008). Thismethod is basing on comparisonof animals remainsthat preserve in caves.The oldest cave profilesare in Račiška pečina, wherewith combination of paleomagneticmethod and palaeontology methoda sedimentary profile was dated to 3.2 Ma.In unroofed cave cut in Črnotiče quarry sedimentswith same methods were about 4 Maold. They were covering remains of cave animalMarifugia cavatica, which was living inthat at the time water cave. This is also theoldest known remnant of the cave animal andwith it we can also reconstruct the paleoenvironmentof that time (Mihevc 2001).43