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Contact karst is a type of karst formed where allogenic waters from the surface influence the karst geomorphic system. Contact karst may be considered in both a strict sense and in a wide sense. In a strict sense, contact karst is the karst phenomena and forms influenced by the contact between a karstifiable rock and a non-karstifiable rock. In a wide sense, contact karst may also be the karst phenomena and forms influenced by the contact between two different karstifiable rocks, for example limestone and dolomite. This thesis focuses on the geomorphological characteristics of contact karst on limestone-dolomite contacts in Slovenia. The purpose of the research was to determine which processes contribute to the development of contact karst on the contact between limestone and dolomite, to define their dynamics, and to identify which surface and underground landforms are developed. The spatial distribution of contacts between limestone and dolomite in Slovenia was determined in a GIS. Using existing lithological data as a data layer, the extent of carbonate rock cover in Slovenia was calculated. Carbonate rocks cover 47 % of Slovenia’s territory (27 % limestone, 14 % dolomite, and 6 % clastic carbonate or impure carbonate rocks). And, there are 1,353 limestone-dolomite contact lines in the country, totalling a length of 2,625 km. Study areas were selected based on GIS analysis of the limestone-dolomite contacts. A total of 17 areas in Slovenia were studied in detail. Fieldwork at the study areas consisted of the collection and analysis of rock, sediment, and water samples, allowing each study area to be geomorphologically mapped. General factors contributing to contact karst development on the lithological contact between limestone and dolomite were determined. The most important factor appears to be the characteristics of the inflow part, formed on the dolomite. Where dolomite functions as a karst rock, the water is dispersedly drained into the karst. In that case, the limestone-dolomite contact does not function as contact karst. Alternatively, where the dolomite functions as fluviokarst, a point recharge, or sinking stream, is formed. In that case, contact karst may be formed. The fluviokarstic character of the dolomite depends on its chemical and mechanical properties. The dolomite bedrock must be positioned at a higher elevation than the neighbouring limestone bedrock. To meet this requirement, dolomite beds, which in Slovenia are generally older than limestone and hence stratigraphically positioned below the limestone beds, need to be positioned above limestone by either folding that leads to inverse stratification, overthrusting, or by displacement along faults. Along faults, the dolomite is more prone to mechanical weathering due to tectonic crushing in addition to its chemical properties. Hence, contact karst is more likely to form at thrust contacts between thrust limestone and dolomite. Limestone-dolomite contact karst develops predominately at higher elevations due to increased precipitation (where allogenic inflow is higher) and greater frost action due to lower temperatures. Intense mechanical weathering of dolomite over limestone directly affects contact karst processes and significantly contributes to the spatial distribution of these types of surfaces. The location of the water table close to the surface is also a leading factor in limestone-dolomite contact karst formation due to enhanced border corrosion. Landforms typical of contact karst were identified in the study areas during geomorphological analyses. However, they are not as clearly recognizable as those on contact between carbonate and non-carbonate rocks. The reason for this is the fact that allogenic waters from dolomitic catchment areas are by far not as corrosive as those from non-carbonate catchment areas. Kontaktni kras je tip krasa, ki nastane na območjih, kjer se površinsko tekoče vode stekajo v kras. V ožjem pomenu kontaktni kras predstavlja kras na stiku med kraškimi in nekraškimi kamninami, v širšem pomenu pa je kontaktni kras tudi kras na stiku dveh zakraselih kamnin, na primer na stiku apnenca in dolomita. V doktorski disertaciji so preučene geomorfološke značilnosti krasa na stiku med apnencem in dolomitom v Sloveniji. Namen raziskave je bil opredeliti osnovne procese, ki vplivajo na nastanek kontaktnega krasa med apnenci in dolomiti, preučiti dinamiko teh procesov in določiti, katere površinske in podpovršinske reliefne oblike se pojavljajo na tem tipu kontaktnega krasa. Z uporabo geografskih informacijskih sistemov je bila določena razporeditev stikov med apnenci in dolomiti v Sloveniji. S pomočjo obstoječih digitalnih prostorskih podatkov je bil določen obseg karbonatnih kamnin v Sloveniji: skupno karbonatne kamnine zavzemajo 47 % državnega površja (apnenci predstavljajo 27 %, dolomiti 14 % ter klastične karbonatne kamnine 6 %). S pomočjo GIS-ov so bile določene t.i. kontaktne linije – območja stikov med apnenci in dolomiti. V Sloveniji je bilo določenih 1353 kontaktnih linij s skupno dolžino 2625 km. GIS analiza je prestavljala osnovo za izbiro vzorčnih območij. V raziskavo je bilo vključenih 17 vzorčnih območij na stiku med apnenci in dolomiti v Sloveniji. Izbrana območja so bila terensko preučena – zbrani in analizirani so bili vzorci kamnin, sedimentov in vode. Za vsako območje je bila izdelana tudi geomorfološka karta. Določenih je bilo nekaj splošnih dejavnikov, ki vplivajo na razvoj kontaktnega krasa na litološkem stiku med apnenci in dolomiti. Na podlagi geomorfoloških značilnosti vzorčnih območij lahko trdimo, da je najpomembnejši dejavnik razvoja preučevanega tipa kontaktnega krasa značilnost dolomitnega hidrološkega zaledja. Na območjih, kjer dolomit deluje kot kraška kamnina, vode razpršeno vtekajo v kras, kar onemogoča nastanek kontaktnega krasa na stiku med apnenci in dolomiti. V primeru dolomitnega porečja, kjer je razvit fluviokraški tip površja, prihaja na stiku z apnencem do točkovnega vtekanja vode v kras. V tem primeru se na litološkem stiku med apnenci in dolomiti lahko razvije kontaktni kras. Način pretakanja vode v dolomitu je pogojen z njegovimi kemičnimi in mehanskimi lastnostmi. Poleg naštetega je ključnega pomena, da se območje, ki ga gradijo dolomiti, nahaja na višji nadmorski višini kot sosednje ležeči apnenci. V splošnem so dolomiti v Sloveniji starejši od apnencev (nahajajo se nižje v stratigrafskem stolpcu), toda za nastanek kontaktnega krasa je ključna lega dolomitov na apnencih. Dolomite, ki se nahajajo na višjih nadmorskih višinah kot apnenci, lahko najdemo na območjih, kjer je prihajalo oz. prihaja do strukturnih premikov površja. Vzdolž prelomnih con je dolomit podvržen intenzivnemu mehaničnemu preperevanju, zato so območja tovrstnih stikov primerna za razvoj kontaktnega krasa. Kras na stiku med apnenci in dolomiti se običajno nahaja na višjih nadmorskih višinah, kjer je povečana količina padavin (večji vtok alogene vode) in nižje temperature, zaradi katerih je dolomit podvržen intenzivnemu mehanskemu preperevanju. Pomembno vpliva tudi lokacija podzemne vode, saj v primeru podzemne vode, ki se nahaja plitvo pod površjem, na območju kontaktnega krasa med apnenci in dolomiti lahko prihaja do pospešene robne korozije. Na izbranih vzorčnih območjih so bile identificirane reliefne oblike, značilne za kontaktni kras, vendar pa te oblike niso tako morfološko izrazite kot na kontaktnem krasu na stiku nekraških in kraških kamnin. |
