engleski

Bathyphreatic characteristics of some large springs in Dinaric karst of Croatia

The Dinaric karst region covers approximately 26000 km2 in Croatia, which is 46% of the national territory. Croatian Dinaric karst is composed of largely prevailing thick carbonate deposits that belong to a stratigraphic range from the Middle Permian to the Eocene. The carbonates are sporadically intercalated by Palozoic, Triasic and Paleogene clastic deposits. The recent geomorphology as well as speleogenesis and evolution of karst aquifers have been strongly affected by Neotectonic deformations. The large thickness of carbonate sediments and intensive tectonic disturbance result in very deep and irregular karstification of the area. Beside numerous surface karst landforms and probably more than 10000 explored caves, the strong karstification of the carbonate rocks is confirmed by appearance of very large karst springs. Maximum yield of these springs can be higher than 100 m3/s. During last decade deep cave diving explorations partly revealed morphology of some of the most significant springs. The exploration results are often surprising and impressive: the conveying karst conduit of the Una spring extends steeply to the depth of more than 205 m, and the Kupa and Sinjac springs extend to the depth of more than 155 m, without reaching the bottom in any of these springs. The significant depths were reached also in the Glavaš springs (115 m, Cetina River), Majerovo spring (104 m, Gacka river), Krnjeza spring (98 m), Kamačnik spring (95 m) and Dubanac spring (94 m). Majority of the mentioned springs have relatively simple morphology (shafts) in the explored sections, and continue to the depth, i.e. divers didn’t reach morphological bottom. The explored sections of some springs show characteristics of deep phreatic looping. In the Majerovo spring looping reaches the water surface, and in the Glavaš spring looping channel is explored to the beginning of ascending section. Based on presented results, it seems that deep phreatic morphology is common and maybe prevailing type in the case of karst springs located in mountainous Dinaric karst terrains. A development of the bathyphreatic channels is probably conditioned by the tectonically active zones, i.e. transcurrent and reverse faulting. Moreover, significant impact is related to the difference in elevation between the recharge and discharge areas that enable high hydraulic potential and consequent deeper water circulation.

Karst spring; bathyphreatic morphology; speleogenesis; Dinaric karst

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