Fluviokarst and classical karst: Examples from the Dinarics (Krk Island, Northern Adriatic, Croatia) Čedomir Benac a , Mladen Juračić b, ⁎, Dubravko Matičec c , Igor Ružić a , Kristina Pikelj b a Faculty of Civil Engineering, University of Rijeka, Dukićeva b.b, 51000 Rijeka, Croatia b Department of Geology, Faculty of Science, University of Zagreb, Horvatovac 102a, 10000 Zagreb, Croatia c Croatian Geological Survey, Sachsova 2, 10000 Zagreb, Croatia abstract article info Article history: Received 3 February 2012 Received in revised form 22 November 2012 Accepted 22 November 2012 Available online 29 November 2012 Keywords: Classical karst Fluviokarst Coastal geomorphology Terra rossa Dinarics Adriatic Sea In order to contribute to the debate on the role of fluvial erosion in the shaping of karst, two nearby areas with different karstic landscapes were compared. Areas A and B are located relatively close to each other on the southern side of the Krk Island (Adriatic Sea, Croatia). Both areas are composed of similar limestone with a very high CaCO 3 content. Area A is a typical doline or polygonal type (“classical”) of karst with numerous dolines (up to 57/km 2 ) cov- ered with terra rossa (red soil) and Mediterranean maquis shrubland. Dolines are located in zones which cor- respond to the strike of the main geological structures. Dry karstic valleys are visible only on gently inclined coastal slopes bordering the karstic plateau. In contrast, area B is typical of a bare karst landscape with a strong (palaeo)fluvial imprint. The dolines are absent, and the bedrock is only sporadically covered with terra rossa. Palaeogene marls have been observed in a few elongated depressions and in the coastal zone of area B. Along steep coastal slopes, valleys (up to 460 m/km 2 ) are cut into the carbonates. The traces of ep- isodic surface flows are visible in some of these valleys, in contrast to the valleys in area A. Remnants of a disrupted ancient fluvial network are clearly visible on the elevated karstic plateau in area B. Differences in the recent morphology are attributed mainly to varying thicknesses of the Palaeogene imper- meable marly cover, and the intensity of tectonics in the two areas. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Hydrologic and hydrogeologic karstic phenomena are fascinating, because it is hard to understand all the factors influencing their devel- opment. Due to irregular and complex connections between the surface and subsurface, water flow in karst often appears confusing. There is an ongoing debate on the role of fluvial erosion in the devel- opment of karst relief (Warwick, 1964; Roglić, 1972; Smith, 1975; White, 1988; Day, 1983, 2002; De Waele et al., 2009; Šušteršič et al., 2009). Most of the karstic forms depend directly or indirectly on chemical weathering (karstification) of soluble rocks marked by a high degree of permeability due to secondary porosity. Pure limestone is considered to be most signif- icant. The karst geomorphologic system differs from others due to the dominant role of dissolution which results in subsurface rather than sur- face water flow (Ford and Williams, 2007). Karst evolution, both at the surface and underground is a complex phenomenon incorporating not only long-range fluvial processes and short-range hill-slope processes but also large-scale chemical dissolution of limestone (Kaufmann, 2002). Fluviokarstic forms develop mostly in the first stages of karstification in areas of intensive rainfall when discharge into a karst system exceeds its conduit system capacity (Deybrodt and Gabrovšek, 2002). During re- construction of the geomorphological development of a karstic area, it is very important to determine as far as possible, the connection between factors of karstification: lithological composition, degree of tectonic defor- mation of rocks, type and degree of karstification of the studied area, cli- matic and sea-level changes during development of the landscape etc. (White, 2002; Audra et al., 2004; Kaufmann, 2009). A mosaic of karst landscapes is observed in the Mediterranean, and especially in the Adriatic region. These variations should be the result of different geolog- ical fabrics, climate conditions and geomorphological evolution (Lewin and Woodward, 2009). The globally important classical Dinaric karst, partly spread across the territory of the Republic of Croatia (Fig. 1), has been described many times since Cvijić (1893) in various publications (e.g. Herak, 1972; White, 1988; Ford and Williams, 2007). However, submerged karst, spe- cifically in the Croatian part of the Adriatic Sea has not yet been described in detail. Only a few results have been published recently (Surić et al., 2005; Benac et al., 2008a; Surić and Juračić, 2010). The aim of this Geomorphology 184 (2013) 64–73 ⁎ Corresponding author. E-mail addresses: benac@gradri.hr (Č. Benac), mjuracic@geol.pmf.hr (M. Juračić), dubravko.maticec@hgi-cgs.hr (D. Matičec), igor.ruzic@gradri.hr (I. Ružić), kpikelj@geol.pmf.hr (K. Pikelj). 0169-555X/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.geomorph.2012.11.016 Contents lists available at SciVerse ScienceDirect Geomorphology journal homepage: www.elsevier.com/locate/geomorph