Szekessy Vilmos (szerk.): A Magyar Természettudományi Múzeum évkönyve 62. (Budapest 1970)

M. Nyírő, R.: Study of the smaller Foraminifera of the Weimpuszta Middle Eocene key section at Nagyesztergár (Bakony Mountains, Transdanubia, Hungary)

ANNALES HISTORICO-NATURALES MUSEI NATIONALIS HUNGARICI Tomus 62. PARS MINERALOGICA ET PALAEONTOLOGICA 1970. Study of the smaller Foraminifera of the Weimpuszta Middle Eocene Key Section at Nagyesztergár (Bakony Mountains, Transdanubia, Hungary) By RÉKA M. NYÍRŐ, Budapest Generalities For a reliable stratigraphie appreciation of the benthonic smaller Foraminifers of the Hungarian Eocene the study of several key sections is indispensable, the stratigraphie position of which has already been established by means of other relevant fossil groups. One of such profiles is the Weimpuszta key section of the 1969 Colloquium on Eocene Stratigraphy. On the basis of large Foraminifers, nannofossils and molluscs it belongs to the Assilina spira and Nummulites perforatus horizons of the Middle Eocene (Lutetian). There is an unconformity between the two horizons, due (according to the team which described the section, G. KOPEK, E. DTJDICH, and T. KECSKEMÉTI, 1969) to near-shore effects of local oscillatory movements. Lithologically, 8 members could be distinguished; facially, however, only 3 major units. These are: an oscillatory (marine-brackish-water) unit, samples 68-100; a freshwater unit, samples 100-102 and 130-133; and a purely marine unit, samples 134-138, the latter being cut in two by the above-mentioned unconformity. The fauna of the smaller Foraminif era, just as the large Foraminifers reflects the facial differences. Accordingly, the faunal assemblages should be discussed following this tripartition. The smaller Foraminifera fauna of the Assilina spira horizon is comparatively poor. The small and thin tests are mostly of poor preservation, due to the overwhelmingly detrital lithofacies. The assemblages consist almost exclusively of benthonic species. Scare planctonic Foraminifers occur in the lowermost sample (68) only. It should be noted, however, that this bed is directly overlying the Middle Cretaceous Turrilites Marl. It may be inferred that the Middle Eocene transgression was rather abrupt, lacking the unusal continental, fresh-water and brackish-water stages of sedimentation. Later on, an opposite trend resulted in a characteristically oscillative, littoral series. As for the planctonic species, Globigerina boweri, Gl. hagni, Gl. inaequispira and Gl. pseudoeocaenica could be identified. Globigerina inaequispira was recorded from the Lower Eocene of the USSR (SUBBOTINA 1958), while from Czechoslovakia it was described from the Lower Lutetian as well (SALAJ and SAMUEL, 1968). The other three are known to occur from the Lutetian onwards to the top of the Eocene. The benthonic Foraminifers are represented mainly by calcareous forms. Arenaceous (agglutinated) forms occur in a considerable number in sample 81 only, in which Clavulina parisiensis is common. The Miliolids accompany the arenaceous forms, abounding in the same sample 81.