Microfauna and nannoplankton below the Paleocene/Eocene transition in hemipelagic sediments at the southern slope of Mt. Nanos (NW part of the Paleogene Adriatic carbonate platform, Slovenia)

This paper describes deeper water clastic to hemipelagic sediments from the Adriatic microcontinent, at the contact zone between the Adriatic and Dinaric carbonate platforms. The flysch section from Mt. Nanos contains a sedimentary sequence deposited close to the Paleocene/Eocene boundary. We dated this section biostratigraphically, reconstructed the paleoenvironments, and established a correlation with the northern part of the central Tethys. Samples were studied for calcareous nannoplankton, planktonic foraminifera, small and large benthic foraminifera, and ostracods. Calcareous nannoplankton assemblages of the Nanos section belong to the Discoaster multiradiatus zone NP 9 in the uppermost Paleocene. Planktonic foraminiferal assemblages allow the assignment to the biozone Morozovella velascoensis (P 5) in the uppermost Paleocene as well. Both nannoplankton and planktonic foraminifera are consistent with a period of global warming in the latest Paleocene just below the PETM. Nannoplankton assemblages are relatively rich in discoasters which suggests that they were deposited in a warm oligotrophic environment. Planktonic foraminifera indicate oligotrophic habitats, warm surface water and a well stratified water column with stable thermocline. Predominance of planktonic foraminiferal species and the presence of the deep-sea ostracod species Cytherella sp suggest sedimentation in deeper opensea environments. A peculiar sphaerical benthic foraminifer – Aberisphaera sp., which has been found in the NE Himalayas and in the Nanos section, possibly indicates a connection between these two geographically remote areas.