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)

The bulk of the calcareous Foraminifers are small-size Cibicides, Discorbis, Anomalina and Nonion species. In the lower beds of the Assilina spira horizon the most common species is Halkyardia minima (a species very numerous in the Middle Eocene). Cycloloculina sp. is restricted to this horizon, being present in a considerable number. The members of the Asterigerina rotula group appear in sample 71, but they become predominant in the N. perforatus horizon only. In the Assilina spira horizon their tests are smaller and thinner, resembling the Rotalia lithothamnica group, which occurs, however, only sporadically in this lower horizon. The Assilina spira horizon has yielded 60 species of smaller Foraminifers. Of these, about 50 are characteristic of the Eocene (cf. Table 1). Alabamina obtusa and A. wilcoxensishave been mentioned in Europe from the Lower Eocene only. In the profile studied, several specimens of both species occur in this horizon. Also Clavulina anglica, CI. cocoaensis and Gyroidina whitei were known to be Lower Eocene species. Long-range species (from the Lower Eocene or even older formations to the Middle Eocene) are Hyperammina nodata, Bolivina crenulata, Cibicides westi, Planulina burlingtonensis neelyi and Elphidium laeve. In the assemblages studied prevail the species described from or abounding in the Lutetian, such as Clavulina parisiensis, Verneuilina muensteri, V. villarensis, Triloculina trigonula, Tr. porvaensis, Lenticulina papilloso-echinata, Bolivina carinata, Siphonina lamarckana, Nonionella spissa, Baggina parisiensis, Discorbis parisiensis, D. limbata, D. vesicularis, Eponides polygonus, Cibicides carinatus, Hanzawaia producta, Halkyardia minima. Some species appear in the Lutetian, but flourish in the Upper Eocene: Quinqueloculina carinata, Qu. ludwigi, Pyrgo bulloides, Seabrookia lagenoides, Tubulogenerina eocaena, Trifarina wilcoxensis, Asterigerina rotula, Anomalina granosa, Eponides truempyi, Sphaerogypsina globula, Missisipina monsouri. The accessory faunal elements of the Assilina spira horizon are omitted from Table 1, because these are not characteristic of the Eocene. These are: Rhabdammina abyssorum, Quinqueloculina juleana, Bolivina semistriata, Uvigerina hantkeni, Elphidium subnodosum, Eponides budensis, E. schreibersii, Cibicides lobatulus, C. propinguus, C. sulzensis, C. ungerianus, Cassidulina subglobosa, Nonion affine, N. scaphum, Gyroidina soldanii, Heterolepa dutemplei. The smaller Foraminifers assemblage of the Assilina spira horizon reveals the closest resemblance to the fauna of the Bruxelles sand, studied in detail by KAASCHIETER (1961). About 30 species are common, and the species abundancies are also very similar. According to the large Foraminifera studies, the Nummulites perforatus horizon begins with sample 137. In fact, the smaller Foraminifera assemblage of this horizon is rather different from that of the previous one. There is a much smaller number of species present; the Asterigerina rotula group is very numerous, the specimens are big and thick-walled. Big-size and massive Rotalia are also common. Both groups need paleontological and stratigraphie revision. Several specimens of Sphaerogypsina globula have also been encountered. Among the accompanying large Foraminifers Lepidocyclina occur, too. It should be noted, that the forms indicative of the Nummulites perforatus horizon appear already below the unconformity (from sample 134 onwards). This Fig. 1. Microfauna of the Weimpuszta Middle Eocene profile Bakony Mountains. (Key Section No 1 of the Colloquium on Eocene Stratigraphy, Hungary 1969)