Evidence for a Late Jurassic Carbonate Platform in the Source Area of the Krčedin Succession (Fruška Gora, Serbia)

The Upper Jurassic–Lower Cretaceous Krčedin succession, situated on the eastern foothills of the metamorphic Fruška Gora Mountains (Serbia), comprises mixed carbonate–siliciclastic deposits, including hemipelagic marlstones, radiolarian-spicule-bearing deposits, carbonate turbidites and breccias. The lower part of the succession is characterized by alternating marly limestones and redeposited shallow-water carbonate material, including partially silicified crinoidal limestones, peloidal limestones, and carbonate breccias containing shallow-water biota. Upsection, marlstone sedimentation becomes dominant and is characterized by pyrite-rich and organic-rich intervals, black shale horizons, and the presence of trace fossils (Chondrites, Planolites). The upper part of the section is represented by quartz-rich siliciclastic turbidites showing a pronounced coarsening-upward trend and is unconformably overlain by transgressive rudist-bearing marly limestones. Thin sections prepared from the carbonate turbidites, and the fine-grained interbedded sediments were analysed for micropaleontological and microfacies data. The redeposited assemblages are dominated by dasycladalean algae, including Salpingoporella pygmaea, Aloisalthella sulcata, and Thaumatoporella parvovesiculifera. The foraminiferal assemblage includes Mohlerina basiliensis, Pseudocyclammina lituus, Redmondoides lugeoni, and Nauticulina sp. The presence of Aloisalthella sulcata, Pseudocyclammina lituus, and Mohlerina basiliensis indicates a (Kimmeridgian–)Tithonian age for the source area of these redeposited shallow-water bioclasts. The studied carbonate turbidites document the existence of a nearby carbonate platform. Late Jurassic carbonate platforms are known from the Dinarides, where carbonate platforms developed on top of the obducted ophiolites, as well as from the Southern Carpathians and related Getic units. However, the entire sedimentary succession of Krčedin is markedly different from successions known from the Getic units or the Balkanides. Therefore, carbonate breccias containing both shallow marine redeposited bioclasts and ophiolitic clasts provide strong evidence for Dinaridic provenance.