Cretaceous to Paleogene agglutinated foraminifera of the Bile Karpaty unit (West Carpathians, Czech Republic)

Assemblages of agglutinated foraminifers ranging from the Aptian to the lower Eocene were studied in the Bile Karpaty unit. One hundred ninety species (43 of them undetermined) were studied taxonomically. The *species Glomospira s traniki and ~ u r r i t e l l e l l a reversa are 'new. Several species of the abyssal "Krashenimikov" fauna (Buzasina inflata, Haplophragmoides decussatus, H . perexplicatus, H . pseudokirki, Recurvoidella insueta, Recurvoides cf. pentacameratus , R . pseudosymmetricus, Plectorecurvoides parvus, Pseudobolivina m u n d a ) previously unknown from the Alpine-Carpathian realm, are recorded for the first time. Other species, previously described from the Romanian and Polish Carpathians, and the Caucasus (Pseudoreophax cisovnicensis , Thalmannammina neocomiensis, Plectorecurvoides irregularis, Uvigerinammina praejankoi etc.), were found in Moravia for the first time. The agglutinated assemblages are compared to the biozones of Geroch & Nowak (1984) and to calcareous nannoplankton and planktonic foraminifera1 data, and a new local biostratigraphic scheme is proposed. Five paleoecologically significant biofacies of mid-slope to abyssal environment are differentiated. The observed sequence of biofacies can be interpreted as gradual basin deepening having its maximum in the Uvigerinammina jankoi Zone and subsequent basin shallowing till the early Eocene. The impact of six paleoceanographic events on the agglutinated assemblages during the Cretaceous and Paleogene are discussed. INTRODUCTION The Bile Karpaty unit (hereinafter denoted by BKU) continues to be an inadequately known facialtectonic unit of the external flysch in the West Carpathians. The understanding of its lithofacial development is complicated by its complex tectonic pattern and its low degree of exposure. A lithostratigraphic classification of the BKU has been recently formalised (EliaS, Schnabel & Strdnik, 1990; Strdnik et al., in press; Potfaj, 1994). The only published taxonomical paper on foraminifers is restricted to the Cretaceous from the Hluk area (VaSiEek, 1947). Calcareous nannoplankton are mostly present only in the younger flysch formations of late Senonian to Eocene age, and were studied by Svdbenickl (1987; 1988; 1990a,b) and by Svdbenickl & Bubik (1992). Within the framework of regional geological exploration of the BKU in the past years, about 400 surface samples and some 300 drill samples were examined for foraminifers. Most of the surface samples have their origin in minor outcrops. Only a few profiles of greater length were available (for the most part in the Vllra succession). Detailed taxonomical studies were made for a set of 174 samples representing all stratigraphic levels from all formations of the BKU. The goal of the studies was the stratigraphical classification of the Cretaceous sediments in which calcareous nannoplankton is mostly lacking. On the other hand, the greater amount of nannoplankton data from flysch formations of late Senonian to early Eocene age allowed to test the applicability of the biozonation of Geroch & Nowak (1984). STUDY AREA The external flysch of the West Carpathians is an -allochthone of nappe structure bordering the Pieniny Klippen Belt towards its foreland. It can be divided into an external (Krosno-Menilitic) and an internal (Magura) group of nappes. The BKU represents the innermost part of the Magura group of nappes (see Fig. 1). In the NW, the BKU is overthrust over the more externally situated RaEa and Bystrica Units while it adjoins the Pieniny Klippen Belt in the SE. In the SW, the BKU disappears below the Neogene sediments of the Vienna Basin and wedges out tectonically in the NE. On the surface, the BKU extends for a distance of 100 km along the direction of the Carpathian belt. Farther to the NE along the Carpathian arc, the BKU is equivalent, due to its tectonic position, to the Krynica Unit (=Orava, Cerchov, and Kochanov Units), whereas towards the SE, in the Wienerwald flysch, it is most likely equivalent to the Laab nappe (ElidS, Schnabel & Strlnik, 1990). In: Kaminski, M.A. Geroch, S., & Gasifski, M.A. (eds.), 1995. Proceedings of the Fourth International Workshop on Agglutinated Foraminifera, Krakow Poland, September 12-19, 1993. Grzybowski Foundation Special Publication no. 3, pp. 71 -1 16.