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Stratigraphic analysis of Paleogene beds in some off-shore wels (Central Adriatic Area, Croatia)

Paleogene sedimentary series deposited in the central Adriatic area should be separated into two different sedimentary realms (tectonostratigraphic units). In the western realm the stratigraphic succession of the deep marine sediments ranges from the Upper Cretaceous to the Middle-Upper Eocene. carbonate turbidites deposited on the deeper part of a platform slope are characterized by the rhythmic exchange of wackestones/mudstone, rich with planktonic foraminifers, and of packstone/rudstone with shallow-water, platform derived detritus (benthic fossils) in the wells Koraljka-1, Ksenija-1, Jadran-1, Jadran-2, Jadran21/l, Jadran-22/1 and Jadran-10. At the end of the Upper Eocene (Priabonian) period the area was drowned and covered by siliciclastic turbidites. According to the distribution of nannofossils and planktonic foraminifera chronostratigraphic continuity is presumed, although there are several hiatuses in the sedimentary record. Nevertheless, this is the most complete succession of Cretaceous to Paleocene sediment ever found in the area of the Outer Dinarides which has no on-shore equivalent. In the eastern realm Paleogene deposits are part of the thick stack of shallow-water carbonates within the Adriatic carbonate platform of the Outer Dinarides. In most profiles a long hiatus between the Upper Cretaceous and the Cuisian is evident (Jadran-9, Jadran-3, Kornati more-2, Susak more-1 wells). Only in the area of Kate-1 well a particular depositional environment, of Maastrichtian and Paleocene age indicates the presence of shallow restricted lagoons that were repeatedly interrupted by short phases of an intertidal regime of emersion and locally influenced by fresh water, at the time of overal regional emersion in Early Paleogene. In the rest of the platform the stratigraphic succession typically starts with a transgression of the uppermost ?Paleocene and/or Cuisian limestone which overlies carstified Upper Cretaceous limestones. After that, a rhythmic change of two different facies within the Cuisian indicates high and low regimes of a tidal flat environment. During Lutetian times, the deposits were sedimented on the shallow, occasionally open platform environment. They were followed by later Lutetian and Bartonian sediments, characteristic of a platform margin. Carbonate deposition stupped at the end of the Lutetian, when the are was drowned under the siliciclastic turbidite deposits.

Paleogene ; Stratigraphy ; Paleoecology ; Tectonics ; off-shore wels ; Central Adriatic Area ; Croatia

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