engleski

Stratigraphy of the Markuševec column (Mt. Medvednica, Croatia)

A Middle Miocene section, i.e. Badenian-Sarmatian as defined within the chronostratigraphical scheme of Central Paratethys Miocene, from the SW part of Mt. Medvednica was investigated in order to provide phytoplankton (coccoliths, diatoms, silicoflagellates and dinoflagellate cysts) zonation. The lowermost part of the 11, 05 thick "Markuševec" section below the unconformity, which is assigned to the Badenian, contains Sphenolithus heteromorphus and other calcareous nannofossils typical for the zone NN5. The same part of the section contains typical assemblages of Serravallian dinoflagellate cysts with its most prominent element Unipontidinium aqueductum. The upper part of the section, above the unconformity, which is assigned to the Sarmatian, is characterized by a sudden decrease in diversity and abundance of the calcareous nannofossil assemblages. The same relations were observed within the dinoflagellate cyst assemblages. The upper part of the section contains silicoflagellate assemblages of the zone Distephanus longispinus and the aquivalent Diatom zone Coscinodiscus plicatus. In the uppermost part of the section the abundance of Ds. crux suggests near-shore temperate environment with seasonal change of the climate ("varva" sediments). The phytoplankton assemblages of the Badenian part of the section clearly indicate that this region of Paratethys was strongly under influence of the Tethys during the Lower Serravallian. The sudden change in the qualitative and quantitative composition of the phytoplankton assemblages of the Sarmatian part of the section represents the first changes towards the individualization of the Paratethys which is almost fully accomplished at the end of the Serravallian, i.e. Sarmatian.

Central Paratethys; Middle Miocene; phytoplankton

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