A Magyarországi Paleogén Medence paleo-oceanográfiája bentosz foraminiferák paleoökológiai vizsgálata alapján = Palaeocanographic history of the Hungarian Palaeogene Basin using a palaeoecological analyis of benthic foraminifera

16 late Palaeogene (Lutetian–Rupelian) boreholes and sections from the Hungarian Palaeogene Basin were investigated for their benthic foraminiferal faunas in order to reconstruct its palaeoecological and palaeoceanographic evolution. In the mentioned ecological interpretation of the temporal distribution of foraminiferal assemblages, multivariate statistical methods were used. These methods included Q-mode principal factor analysis (PFA) and BFOI (Benthic Foraminiferal Oxygen Index) analysis. On the basis of the Q-mode principal factor analysis, the faunas are characteristic for inner neritic (0–30 m water depth) to upper bathyal environments (approximately 30–500 m water depth). The composition of the benthic foraminiferal fauna and the results of the Q-mode principal factor analysis indicate tropical–warm conditions from the beginning of the Middle Eocene. A change in the temperature of the bottom water can be detected from the late Middle Eocene time, and estimated temperatures indicate temperate–cold conditions during this period. On the basis of the BFOI (Benthic Foraminiferal Oxygen Index) analysis, the Middle and Late Eocene are characterised by two short eutrophic events (POMZ1 and POMZ3) and two significant eutrophic (POMZ2 and POMZ 4) events. These periods are characterised by evidence of a low diversity of fauna, with a high dominance of lowoxygen tolerant (infaunal) species. The eutrophic events suggest that there was a second-order sea-level fall and restricted deep water circulation, while the oligotrophic and high oxic conditions might have been caused by colder, welloxygenated bottom water masses from the SE Tethyan Realm. Evidence suggests that these oligo- to mesotrophic periods were characterised by a high diversity of fauna, with a signifcant dominance of epifaunal species. The initial stage of the significant subsidence history coincides with the POMZ2 period at the end of the NP17 zone. This demonstrates clearly that the evolution of the Hungarian Palaeogene Basin was strongly influenced by significant palaeoceanographic events