Webbinelloidea similis Stewart et Lampe (Foraminiferida) z eiflu synkliny łagowskiej (Góry Świętokrzyskie)

Jan Malec


 Z dolomitów dolnego eiflu (otwór wiertniczy Zaręby 102) opisano zlepieńcowate otwornice gatunku Webbinelloidea similis Stewart et Lampe, wśród których wyróżniono 3 grupy i 6 podgrup morfologicznych i porównano je z analogicznymi morfotypami W. similis Stewart et Lampe z innych obszarów Gór Świętokrzyskich. Badane otwornice umożliwiły zaliczenie stropowej części osadów terygenicznych z Zaręb, uznawanych dotąd za dolnodewońskie, do dolnego eiflu.




The borehole Zaręby IG 2, situated in central part of the Góry Świętokrzyskie Mts (Fig. 1), penetrated complete sequence of Devonian rocks, from the Upper Famennian to ? Lower Emsian, inclusively (H. Jurkiewicz, 1971; H. Żakowa, 1971; M. Tarnowska, 1976). Basal part of the section is built of terrigenous rocks, occurring in sedimentary continuity with overlaying dolomites. The series of terrigenous rocks was subdivided into 4 characteristic lithological complexes: two mudstone complexes with tuffites and two sandstone ones (M. Tarnowska, 1976).

The studies carried out by the Author were concentrated on lower part of the Devonian section, i.e. Lower Eifelian dolomites and rocks of upper terrigenous complexes, dated at the Lower Devonian (Emsian). Numerous agglutinated foraminifers of the species Webbinelloidea similis Stewart et Lampe have been found in dolomites from depths 1029.7-1030.8 m and 1065.4-1066.4 m and a meter layer of marly dolomites from depth 1097.7 -1098.7 m. Within the assemblages of W. similis Stewart et Lampe, some morphological groups were differentiated (Fig. 1) with reference to the scheme proposed by J.E. Conkin, B.M. Conkin (1970). Besides differences in numbers of specimens in individual assemblages, foraminifers from the depth 1029.7-1066.4 m were found to be characterized by generally more convex tests than those from the depth 1097.7-1098.7 m (Figs. 1, 2). The recognition of distribution of morphotypes of W. similis Stewart st Lampe in Lower Eifelian section in western part of the Góry Świętokrzyskie Mts (J. Malec, 1982, 1984) made possible more precise dating of the studied strata from the Zaręby area. The record of Lower Eifelian foraminifers at the depth 1097.7-1098.7 m showed that the Lower-Middle Devonian boundary should not be drawn at the depth 1080.1 m but greater, at least at 1098.7 m (Fig. 1). It is highly probable that the rocks of the upper mottled complex down to the depth of 1131.4 m are of the Lower Eifelian age.

Morphotypes of W. similis Stewart et Lampe, similar to the above described, are also known from the Lower Eifelian in northern region of the Góry Świętokrzyskie (unpublished data of the Author).

Comparison of the morphotypes showed that dolomites overlaying the upper sandstone complex at

Zaręby correspond in age to those resting directly on dolomites above limestone of the Chimaerothyris

dombrowiensis zone in. the Grzegorzowice section.


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