Mikrofauna utworów trzeciorzędowych serii poznańskiej Dolnego Śląska

Ewa Łuczkowska, Stanisław Dyjor


Tertiary microfauna of the Poznań clays in Lower Silesia

Three lithofacial members differing in genesis, petrology, mineral composition and colour were distinguished within the Tertiary Poznań Clays in the Fore-Sudetic area (Fig. 1 and Fig. 2). Taken in order from the base these are: 1) grey clays, 2) green clays containing glauconite, 3) red clays. A foraminiferal microfauna was found in the middle member, i.e. in the green clays, in three bore-holes, at Wołów (NW of Wrocław), at Borek Strzeliński (S of Wrocław) and at Tarpno (N of Góra). The richest microfauna was found at Wołów, at depth of 80 m, 115 m, and 116 m. The assemblage have a similar composition and consist of Bulimina elongatar B. gibba, B. inflata, B. striata, Valvulineria complanata, Turborotalia mayeri, T. opima, T. scitula, Globigerina ampliapertura, G. bulloides, and several species of the genera Stilostomella, Uvigerina, Elphidium and others (altogether 38 species — Table 1, Plate V III—XI). Comparisons with other microfauna assemblages of Miocene and Pliocene age indicate that the microfauna from Wołów is of Miocene age. Thus its presence in rocks usually regarded as belonging to the Pliocene, suggest the necessity of revision of the age of the Poznań Clays. Furthermore, the presence of microfauna suggests the existence of a connection between the sedimentary basin of the Poznań clays series and the marine basin of the Carpathian Foredeep, probably through the Nysa embayment. It is supposed that short-lasting ingressions of the Tortonian sea into the sedimentary basin of the Poznań Clays brought in the foraminiferal microfauna, but did not create conditions favourable for its stronger development.

Full Text: