engleski

Slope carbonates within the Adriatic-Dinaridic Carbonate Platform domain (central Dalmatia, Adriatic region of Croatia)

The Upper Cretaceous carbonate succession on the Island of Čiovo in central Dalmatia (Adriatic region, Croatia) differs from the typical platform development in the region (e.g., the Sumartin Fm on the neighbouring Island of Brač), implying a different depositional setting. Several methods, including integrated stratigraphy (litho-, bio-, and chemo-stratigraphy of C and Sr isotopes) along with petrological analysis, are being used to constrain the regional stratigraphic correlation. Approx. 300 m thick succession of Cretaceous carbonates is measured and analyzed on the westernmost coast of the island. The lower part of the succession is referred to as the Dol Fm of Campanian age, characterized by pelagic bioclastic W/P with chert nodules and rare allochthonous intercalations. Depositional setting of the Dol Fm is presumed to be toe-of-slope/slope. Two Campanian discontinuity surfaces (hard-/firm-grounds) occur in the uppermost part of the Dol formation. These surfaces will be analysed using several methods (including C isotope stratigraphy) to explain their genesis and to determine their possible correlation to some global eustatic/isotopic event. The upper part of the succession is in general represented by massive to thick-bedded resedimented allochthonous grainy limestones. These are mostly bio-lithoclastic P (rarely G/R) with predominantly echinoderm fragments (crinoids, echinoids) with syntaxial overgrowths, mollusk fragments (rudist), benthic foraminifera, bryozoans, coralinacean algae, lithoclasts, and pelagic admixtures. This part of the succession was deposited in slope/toe-of-slope settings, as also indicated by the benthic foraminfera assemblage. This assemblage is represented by Siderolites calcitrapoides, Lepidorbitoides sp., Pseudosiderolites vidali, Orbitoides tissoti/media, and Vanderbeekia catalana indicating late Campanian (?Maastrichtian) age. During subaerial exposure “paleokarstic pockets“ in the form of paleosols with Microcodium structures developed in the uppermost ~10 m of this Upper Cretaceous succession, which is unconformably overlain by the transgressive Paleogene (?Eocene) Foraminiferal limestones over the regional type 1 sequence boundary. Although the depositional setting and lithology of the upper part of the Čiovo succession can be correlated with that of the Brač „marble“ member of the Pučišća Fm or „atypical“ allochthonous facies (Dračevica) of the Dol Fm on the Island of Brač, the stratigraphic range and the relationships with overlying strata require establishment of a new formation, which is called here the Čiovo formation. While the Sumartin Fm on the Island of Brač represents a typical inner-platform development, penecontemporaneous deposits of the Čiovo Fm likely represent deeper water slope/toe-of-slope depositional settings, presumably facing the NE Adriatic trough).

lithostratigraphy; biostratigraphy; chemostratigraphy; slope carbonates; carbonate platform

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