engleski

Lithological and structural controls of cave development on Kornati Islands,Croatia

Kornati Islands archipelago encompasses 91 carbonate islands and islet situated in the central part of eastern Adriatic coast in Croatia. They are predominantly composed of deformed Upper Cretaceous to Eocene pre-orogenic carbonates and stretch parallel with the coast in NWSE, i.e. Dinaric direction.In order to contribute to the knowledge of the speleogenesis of the Kornati Islands caves, 45 caves (42 pits and 3 caves) have been identified and analysed during a three year research project of cave inventarization. In this research we aim to identify if the ”inception horizon” exist and to connect cave forming to lithological or chemical deviation from the predominant carbonate facies within the surrounding sequence or to structural and tectonic elements. Geological structures above and within the caves were measured. Petrographic analysis of geological samples taken in the cave and on the surface were done in order to determinate inception horizons and how they influence cave geometry. Based on collected data a GIS analysis on cave density, distribution, vertical position has been performed. Spatial analysis of the cave distribution show higher density of the in the west coast of Kornati islands between 1 and 60 m a.s.l. while some of the cave extend below sea-level up to 45 m of depth. Based on the hydrological characteristics nine caves have no water and 36 caves are partially (22 anchialine caves) or completely submerged (10 sea caves). Analyses of the cave passage orientation indicate that most of the analysed caves are dissolution caves with dominant NW-SE orientation. This reveals dominant influence of neotectonic stress related to the Adria microplate underthrusting the Southern Alps. The intensive folding of the Islands and several identified faults caused development of secondary porosity that significantly influenced speleogenisis of Kornati islands caves. Results show existence of a favourable structures, unrelated to today’s surface topography, where a more intensive dissolution processes have occurred. This sequence extends approximately 60 m a.s.l. and 50 m below today’s sea level. This karstification processes probably began along expansion fracture in zone of axial surface and subvertical bedding planes.

spelegenesis, inception theory, caves, kars, Croatia

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