Informace o publikaci
Evolution of Eoparastaffella and the Tournaisian-Visean boundary in Mokrá near Brno (Czech Republic)
| Autoři | |
|---|---|
| Rok publikování | 2003 |
| Druh | Článek ve sborníku |
| Konference | International Congress on Carboniferous and Permian Stratigraphy |
| Fakulta / Pracoviště MU | |
| Citace | |
| Obor | Geologie a mineralogie |
| Klíčová slova | Foraminifers; Tournaisia/Visean boundary |
| Popis | The subgenera of Eoparastaffella have been studied together with morphologically very close Eoendothyranopsis in profiles of the Tournaisian-Visean boundary beds in the Mokra quarries (Moravia, Czech Republic). The profiles are composed both of the alternation of limestones and red to green shales and the alternation of biodetrital and biomicritic limestones with thin shale intercalations. The joint presence of shallow water bioclasts (foraminifers, algae, calcispheres, crinoids, rugose corals etc.) and deeper water fauna (conodonts - abundant gnathodids, Scaliognathus, trilobites) as well as apparent gradations suggest that most of the limestones can be regarded as calciturbidites. The sediments correspond to different parts of a halfgraben basin; they were deposited in the beginning of a compression regime cycle and represent a transition to overlying typical flysch sequences. The different facies are folded and convergent in complicated overthrust tectonics. The shales contain locally abundant trilobites and brachiopods, ammonites are less frequent. In the lower part of the sequences, biodetrital often sandy limestones predominate, the proportion of biomicritic limestones increases to the top of the profile. Dominant microfacies are packstones and wackestones; grainstones are less frequent. The matrix of grainstones consists of microsparite and pseudosparite, partly resulting of the recristallization of the original micritic matrix. Crinoids are the most abundant bioclasts, foraminifers, grains of quartz, calcispheres, ostracodes, red algae (Solenoporaceae), moravamminids, brachiopods, bryozoans, trilobites, blue-green algae, trilobites, bivalves, intraclasts and conodonts occur as well. The quite frequent conodont taxa belong to the Scaliognathus anchoralis Zone and the Gnathodus texanus Zone of the standard conodont zonation. Nevertheless, neither Gnathodus texanus (ROUNDY, 1926) nor Gnathodus homopunctatus ZIEGLER, 1962 have been found so far and Mestognathus beckmanni BISCHOFF, 1957 represents the only typical Visean species. In the uppermost Tournaisian part of the profile Eoendothyranopsis and Eoparastaffellina is frequent while Eoparastaffella representatives predominate in the Visean. Eoparastaffella simplex VDOVENKO, 1954 is the most frequent species coexisting with E. ovalis VDOVENKO, 1954 and E. iljtchiensis POSTOJALKO, 1975. E. evoluta VDOVENKO, 1971 and E. pseudochomata VDOVENKO were determined from older samples. Among evolutionary older eoparastaffellins Eoparastaffellina rotunda VDOVENKO, 1971 was distinguished both below and above the Tournaisian-Visean boundary. The taxonomic assignment of some eoparastaffellins as well as the distinction between some eoparastaffellins and Eoendothyranopsis (Ninella) is still a matter of research. The following species of Ninella have been recognized in the profiles: E. (Ninella) donica BRAZHNIKOVA et ROSTOVTSEVA, 1964, E. (Ninella) lebedevae SOLOVIEVA, 1967, E. (Ninella) moravica ONDRACKOVA, 2001, E. (Ninella) aksarsaica MICHNO, 1975, E. (Ninella) transita LIPINA, 1955. The first occurrence of Mestognathus beckmanni BISCHOFF, 1957. has been recently found, contrary to the previous data of Kalvoda & Ondrackova (1999), below the entry of E. simplex VDOVENKO, 1954. Between the first occurrence of Mestognathus beckmanni BISCHOFF, 1957 and the last occurrence of Scaliognathus anchoralis BRANSON & MEHL, 1941 stratigraphically diagnostic species are lacking. The conodont fauna at this level is characterized by the abundance of Gnathodus (Gnathodus Horizon - see Fig. 1). A similar horizon can be distinguished also in the Pengchong section (Guangxi Autonomous Region, South China) (Sevastopulo et al. 2002). |
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