Timing of Langhian bioevents in the Carpathian Foredeep and northern Pannonian Basin in relation to oceanographic, tectonic and climatic processes

Abstract

The succession of bioevents in planktonic foraminifer and calcareous nannoplankton communities is reviewed and summarized for the Carpathian Foredeep and northern Pannonian Basin in the time interval between ~16 and 13.5 Ma. This succession can be subdivided into three principal intervals: (1) an interval with rare Praeorbulina sicana and P. glomerosa. It was characterized by a limited immigration of index taxa linked to the lack of a warm surface water layer in the Central Paratethys. This interval can be correlated with the first Badenian transgression near the Burdigalian/Langhian boundary. The rare occurrence of biostratigraphical markers does not allow its precise dating and interregional correlation; (2) a brief interval of the first occurrences of Praeorbulina circularis, Orbulina suturalis and Helicosphaera waltrans. This can be related to the formation of a warm surface water layer suitable for the survival of orbulinas and praeorbulinas and a change from estuarine to anti-estuarine circulation. This interval can be correlated with the second Badenian transgression, which, however, was not isochronous over the area as inferred from different successions of these first occurrences; (3) a limited appearance of new index taxa in the Central Paratethys prior to the Wielician Salinity Crisis. This time interval was characterized by increased seasonality and salinity oscillations followed by climate cooling. A “reverse” migration of the stress-tolerant species Helicosphaera walbersdorfensis from the Central Paratethys to the Mediterranean is suggested. Several local bioevents with limited stratigraphic correlation potential have been recognized in this interval.