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Basic Geology of the Krka National Park

The area of the Krka National Park is composed of Upper Cretaceous and Palaeogene carbonate rocks. Upper Cretaceous sequence is composed of two lithological units: older late-diagenetic dolomites and younger rudistid limestones, while Palaeogene deposits consist of foraminifera limestones, transitional beds, flysch and clastic– carbonate Promina deposits (Mamužić, 1971). Late-diagenetic dolomites crop out at SW and NE coasts of the Prokljan Lake in the cores of the anticlines. These are middle- to coarse-crystalline dolomites with interbeds of uncompletely dolomitized recrystallized limestones, but all fossil remains are destroyed by late-diagenetic processes. Age of this unit was determined by correlation with limestones of Middle Cenomanian– Coniacian age which probably represent their lateral equivalent. Rudist limestones are represented by continuous succession of light-brown limestones composed of alternation of middle- to thick-bedded mudstones, peloid– fossiliferous packstones with aeolisaccus and thaumatoporella, fenestral mudstones, foraminiferal wackestone/packstone/grainstones, rudist floatstones and rudist coquinas. Stratigraphic range of this unit is Late Turonian/Coniacian to Late Santonian/Early Campanian. Besides numerous rudists, among which radiolitids and hippuritids are the most important, very important is the benthic foraminifera assemblage with Dicyclina schlumbergeri MUNIER-CHALMAS, Keramosphaerina tergestina (STACHE) and Murgella lata LUPERTO-SINNI. Described deposits were accumulated in peritidal and subtidal environments of the Adriatic Carbonate Platform. Palaeogene foraminifera limestones are represented by variable litho- and biofacies, depending on the actual position on the carbonate ramp during the Early and Middle Eocene: miliolida and alveolina limestones in restricted and more open shallows, nummulite and discocyclina limestones and transitional beds (marls with crabs and glauconite) on slopes of carbonate ramps, and sandstones and marls alternation in deeper parts of the Middle Eocene flysch troughs. Promina clastic– carbonate deposits represent a continuous regressive succession of Late Eocene– Oligocene age, from deeper marine, shelf and coastal deposits, including typical heavily bioturbated limestones, to fine- and coarse-grained clastics – conglomerates, sandstones and marls deposited within braided rivers environments. Area of the Krka National Park, as well as surrounding Ravni Kotari and Dalmatinska Zagora areas, represent intensely folded part of the Karst Dinarides with characteristic strike of the structures NW– SE (so-called Dinaric strike). Cretaceous rocks usually form anticline cores, while Palaeogene rocks built syncline limbs. Faults are mostly reversed and subparallel to the strike, and commonly of SW vergence.

Upper Cretaceous; Rudist limestones; Palaeogene carbonates; flysch; castic-carbonate promina deposits

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