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Kita Gaćešina Cave System What we know about the longest Croatian cave?

Intensive speleological research on Mt. Crnopac in last decades resulted in 2004. with the discovery of the longest Croatian cave, Cave system Kita Gaćešina – Draženova puhaljka. The length of the cave is 22 519 m and the depth 665 m. The main morphological characteristic of the cave is a network of multiphase cave passages, some of them with very large cross-section dimensions. Estimated cave volume is 1.3 million m3. The exploration of the cave was conducted by the members of The Speleological Committee of the Croatian Mountaineering Association. From 2004 to 2012 there were 70 explorations with 181 cavers from 27 clubs from Croatia and Slovenia, France and Serbia. Cave map has 3106 survey stations with average distance of 8.5 m, average cross section 7.6 m and average inclination 30.6 degrees. Furthest Station is 2470 m from the entrance. Crnopac massif is the most southern part of the Velebit mountain range (part of Dinaric coastal mountainous karst, SW Croatia). The massif is built of thick carbonate deposits of upper Triassic, Jurassic and Cretaceous age. Speleogenesis of the caves in the Crnopac massif probably have lasted continuously from the beginning of the massif uplift (upper Miocene ?). The massif is situated between higher terrain of Gračac polje on the north and Zrmanja River valley on the south and east. In such conditions polygenetic multilevel caves have developed inside the carbonate massif. Presently known caves are the remnants of various levels of paleodrainage systems that conducted waters from the higher terrain on the north to the base level springs on the south and south-east. Older phreatic and epiphreatic channels are frequently crossed by younger invasion vadose shafts, which provide entrances to the most of explored caves and also connections between different levels inside the caves. Mechanical properties of the Oligocene to Lower Miocene carbonate breccias have significant role in the cave morphology. Low frequency of cracks and joints in these massive breccias enables preservation of underground passages and chambers of very large dimensions. Moreover, cave channels developed in breccias generally have well preserved phreatic and epiphreatic morphology, while collapsing processes are more expressed in channels developed in older carbonate rocks. Fluvial sediments are present in the majority of paeleophreatic channels, and sediment exploration in the future would greatly contribute to the understanding of cave genesis. Complex speleogenesis produced a polygenetic multilevel system that has a key influence to present cave microclimate and hydrology. The measurements of the cave microclimate, radon concentration and water quality parameters will help to understand important processes in the cave.

geology ; hydrology ; speleology ; cave climate ; radon ; Dinaric karst ; Croatia

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