engleski

Planktonic Foraminiferal Biostratigraphy and Paleoecology of The Middle to Upper Eocne in the North Adriatic Sea (Croatia)

The succession studied was deposited within eastern part of the Venetian Basin (north Adriatic Sea, Croatia). Three deep exploration wells were drilled through the Middle and Upper Eocene, pelagic and hernipelagic deposits (limey marls in the lower part and marls and silty marls in the upper part). The basinal evolution from Middle to Upper Eocene indicates a generalized regressive trend. Planktonic foraminiferal assemblages of the Middle to Upper Eocene enable the recognize of all planktonic foraminiferal Zones (P10 to P17). Beside zonal markers, evolutionary lineage of the Turborotalia cerroazulensis group as well as the species succesion of the genus Globigerinatheka were usefull for biostratigraphic analyses. Two different types of planiktonic assemblages were observed: association with only a few genus (Subbotina, Turborotalia and Globigerinatheka) and association with great diversity and occurrence of muricate species (Morozovelia, Acarinina, Truncorotaloides). Paleoecological factors which controlled composition of the association probably were temperature and thropic resources. The association are generally both rich in individuals and high diversified, but the marker species such as Morozovella lehneri, Orbulinoides beckrnanni and Hantkenina spp. are rare or absent. The specimens of other species, such as Globigerinatheka semiinvoluta possess small test and smaller number of secondary apertures. The test of all species found were smaller than the test of the same species found in low latitude area. All these facts, the test morphology and diversity of the planktonic foraminiferal assemblages indicate to the Mediterranean bioprovince with a subtropical warm-temperate climate.

Foraminifers; Stratigraphy; Tertiary

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