The Pannonian Basin, originating during the Early Miocene, is a large extensional basin incorporated between Alpine, Carpathian and Dinaride fold-thrust belts. Back-arc extensional tectonics triggered deposition of up to 500-m-thick continental fluvio-lacustrine deposits distributed in numerous sub-basins of the Southern Pannonian Basin. Extensive andesitic and dacitic volcanism accompanied the syn-rift deposition and caused a number of pyroclastic intercalations. Here, we analyze two volcanic ash layers located at the base and top of the continental series. The lowermost ash from Mt. Kalnik yielded an 40 Ar/ 39 Ar age of 18.07 ± 0.07 Ma. This indicates that the marine-continental transition in the Slovenia-Zagorje Basin, coinciding with the onset of rifting tectonics in the Southern Pannonian Basin, occurs roughly at the Eggenburgian/Ottnangian boundary of the regional Paratethys time scale. This age proves the synchronicity of initial rifting in the Southern Pannonian Basin with the beginning of sedimentation in the Dinaride Lake System. Beside geodynamic evolution, the two regions also share a biotic evolutionary history: both belong to the same ecoregion, which we designate here as the Illyrian Bioprovince. The youngest volcanic ash level is sampled at the Glina and Karlovac sub-depressions, and both sites yield the same 40 Ar/ 39 Ar age of 15.91 ± 0.06 and 16.03 ± 0.06 Ma, respectively. This indicates that lacustrine sedimentation in the Southern Pannonian Basin continued at least until the earliest Badenian. The present results provide not only important bench marks on duration of initial synrift in the Pannonian Basin System, but also deliver substantial backbone data for paleogeographic reconstructions in Central and Southeastern Europe around the Early-Middle Miocene transition.

The sequence of Miocene fossiliferous marls of the Crnika beach, along the south west shore of Pag Bay, consists of an alternation of silty and clayey marls, sandstones, coaly clays, coal-bearing strata and sparse intercalations of bentonite in the older part, and of an alternation of calcitic marls and organogenic fossiliferous limestones with several coal strata in the younger part. Some of the strata are highly fossiliferous and rich in various species of freshwater gastropods of the genera Melanopsis, Theodoxus, Pyrgula, Prososthenia, Orygoceras and Valvata with the new species V. (?Costovalvata) pagana. Bivalves are represented by the genera Congeria, Unio, Pisidium. There is also, a rich ostracod assemblage, and remains of fl ora: twigs, leaves and seeds of higher and lower plants, and agglomerations of aquatic grasses and algae. Fish bones and teeth, as well as the crocodile tooth, are not particularly common, but they do help to complement the image of the diversity of the biological association that lived in the ancient lake and along its shores. According to facies analysis, the Miocene deposits of the Island of Pag, were deposited on the southwestern edge of Paratethys, which has been moved more westward and south-westward within Croatian territory.

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