CALCAREOUS NANNOFOSSILS FROM THE PETM INTERVAL OF A SHELF SECTION IN JORDAN

The Paleocene-Eocene Thermal Maximum (PETM) was a period of global warming at ~55 myr, which was accompanied by major alterations in the ocean-atmosphere system. A detailed quantitative study of calcareous nannofossils was carried out for the PETM in northeast Jordan. The calcareous mudstones recovered by a core reflect a shelf setting on the southern margin of the Tethys Ocean. The δ13C_org isotope signal and the distribution patterns of the calcareous nannofossils were used to characterize the surface water conditions during this hyperthermal event in Jordan. The response of calcareous nannofossils during the PETM interval is characterized by the first occurrence of deformed nannoliths (Discoaster araneus, Rhomboaster spp.) known as “excursion taxa”. These go along with high abundances of Coccolithus pelagicus and Toweius spp. and low abundances of Chiasmolithus spp., Neochiastozigus spp., Discoaster spp., Fasciculithus spp. and Sphenolithus spp.. This indicates availability of nutrients in the surface water. The upper part of the post-PETM interval displays an increase in the abundance of Sphenolithus spp. and a decrease in abundance of the other taxa. This suggests a decrease of nutrient availability, thereby reflecting a short termed oligotrophic event. The described turnovers of the calcareous nannofossil assemblages reflect a biotic response to global climatic changes well known from the PETM, which are related to the massive release of CO₂ into the ocean. In addition regional factors like increased run-off and changes of the nutrients fluxes played a role as well.