Dolnodewońskie tentakulity z otworu wiertniczego Ciepielów IG-1

Barbara Hajłasz




Bore hole Ciepielów IG-l has pierced the Lower Devonian deposits in which tentaculites occur (Fig. l). At a depth of 2135.8-2406.0 m (Fig. 2) the author has distinguished two assemblages of tentaculites. In the first assemblage, found at a depth of 2406.0 – 2311.0 m, the following representatives occur: Tentaculites gyrocanthus Eaton (Table II, Figs. 8-10, Table VIII, Fig. 40), Tentoculites nikijforovae G. Ljasch (Table IV, Figs. 20-22, Table VI, Fig. 23, Table VIII, Fig. 4l), Tentaculites estonicus G. Ljasch (Tab1eVI, Fig. 23), Tentaculites sp. (Table II, Fig.11, Table VII, Figs. 34-35), Heteroctenus opiparus sp. nov. (Table V, Figs. 26-28, Table VI, Fig. 30) and Heteroctenus sp. (Table IV, Figs. 24-25). The tentaculites of the first assemblage resemble that descrilbed by G. P. Ljaschenko from Podolia and from the Peri-Baltic area. Tentaculites gyrocanthus Eaton and Tentaculites nikiforovae G. Ljasch occur in the Podolia in the beds of the Czortkowski horizon. In Poland, to the Czortkowskie beds correspond the Bostowskie beds referred in 1962 by E. Tomczykowa and H. Tomczyk to Gedinnian. The second assemblage that occurs at a depth of 2311.6-2135.8 m is characterized by dying out of the tentaculites of the first assemblage, among which only one species Tentaculites gyrocanthus Eaton passes upwards. On the other hand, new species can be observed: Tentaculites antarcticus Fisher (Table II, Figs. 5-7, Table IX, Figs. 42-43), Tentaculites cf. attenuatus Hall (Table I, Fig. 1-2), Tentaculites formosus sp. nov. (Table II, Fig. 32, Table VII, Fig. 33), Tentaculites absimilis sp. nov. (Table II, Fig. 13, Table III, Figs. 14-18, Table VIII, Figs. 36-39) and Tentaculites mirabilis sp. nov. (Table III, Fig. 19). All the species mentioned above are very abundant and occur at a depth from 2311.6 to 2212.9 m, whereas from 2221.9 to 2135.8 m they are rarely found; and the species are distinctly poorer. Since Tentaculites gyrocanthus Eaton is of large extent (Silurian - Devonian), and Tentaculites attenuatus Hall is known to occur in North America in the Hamilton formation, and the remaining species that belong to this assemblages are new, no basis exists at present to draw any startigraphical suggestions. It is possible that a change in ecological conditions has taken place, and this has influenced the disappearance of the tentaculites of the first assemblage in the Gedinnian deposits. Thus, a suggestion may be made that the second assemblage no doubt younger, is of Siegen age. The disappearance of tentaculites, accompanied by impoverishment of the remaining fauna, points to a gradual transition from marine to continental conditions that predominated already at the Upper Siegen time.

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