Nowe dane o karbonie w okolicy Bolechowic i Kowali (Góry Świętokrzyskie)

Abstract

 Opisano trzy – po kilka metrów miąższości – różne stratygraficznie profile karbonu dolnego. W otworze wiertniczym Kowala 1 występują osady facji marglistej należące do turneju dolnego z obfitą makro- i mikrofauną oraz konodontami, kontaktujące z najwyższym famenem. Górnoturnejskie utwory ilasto-krzemionkowe z radiolarytami i konkrecjami fosforytowymi, syngenetycznymi z osadem, uzyskano w otw. BZ 1 a osady facji tufogenicznej w otw. BZ 2. Zaliczono je, z zastrzeżeniem, do wizenu dolnego, nieznanego dotąd w synklinie bolechowickiej. Badania petrograficzne potwierdziły też genetyczny związek radiolarytów i przejawów wulkanicznych. Materiał tufogeniczny i charakter chemiczny tufów wskazują na ich związek z wulkanizmem kwaśnym typu ryolitowego.  NEW DATA ON THE CARBONIFEROUS IN THE VICINITIES OF BOLECHOWICE AND KOWALA (GÓRY ŚWIĘTOKRZYSKIE MTS.) Three sections of Lower Carboniferous rocks of different age are described from drillings made in the Bolechowice Syncline, SW part of the Góry Świętokrzyskie Mts (Fig. 1). In the borehole Kowala 1, beneath the Quaternary, there have been encountered marly-calcareous rocks of the Gattendorfia stage (3.1 m thick), resting on claystones and marly limestones of the Bispathodus costatus zone (H. Żakowa, M. Nehring-Lefeld, 1983). The paleontological record of the Carboniferous includes microfauna, Tetracoralla, Chonetidae, Orbiculoidea sp., numerous specimens of Archegonus (Waribole) abruptirhachis (R. et E. Richter), bivalves, e.g. Guerichia mariannae (Tchernyshev), G. venustiformis (Sadykov) mass occurrences, and conodonts including Protognathodus kockeli (Bischoff). This has been the second record of the “Protognathodus fauna” elements (after that from Gałzice - M. Szu1czewski, 1978). Selected representatives of that fauna are figured in Plate 1.In the borehole BZ 1 and BZ 2, situated in the proximity of the old borehole Bolechowice IG 1 (H. Żakowa, 1967; G. Freyer, H. Żakowa, 1967), the. Carboniferous has been encountered beneath the Permian. Orbiculoidea tornacensis Demanet, index fossil of the Upper Tournaisian, has been found in the borehole BZ 1 (PI. I, Fig. 6). The age of the strata was precised on the basis of detailed lithological and petrographic studies (PI. I, Figs. 8, 9; PIs. II - V; Table 1; Fig. 2) and correlations with Carboniferous sections from the boreholes Bolechowice IG 1 and Jabłonna IG 1 in the Borków Syncline, about a dozen km east of the studied area (H. Żakowa et al. 1983).Carboniferous strata from the borehole BZ 1, dated at the Upper Tournaisian, include rocks of clay-siliceous facies with radiolarites (up to 2 m in thickness) and very numerous phosphatic nodules, variable in shape, as well as intercalations of radiolarite breccias, tuffogenic laminae, pyrite nests and calcite veinlets. Nodules are genetically related to radiolarites. Their syngenetic character is shown by both relation to surrounding rock (noticeable laminar enveloping structures) and presence of well preserved radiolarians in nodules built of collophane mass. The section from the borehole BZ 1 is correlable with that of the Upper Tournaisian (Zaręby Beds) in the boreholes Bolechowice IG 1 and Jabłonna IG 1.The Carboniferous section from the borehole BZ 2 is characterized by intercalations of benthonitized,vitroclastic benthonitized and vitrocrystaloclastic tuffs and clay-siliceous rocks, separated by cherry-red claystones. Analogical strata are known from the borehole Jabonna IG 1, where they are dated at the Lower Visean with reservation. The above similarity suggests that the strata may be coeval with the latter. This would supply a new element to the knowledge of stratigraphy of the Carboniferous in the Bolechowice Syncline, wherefrom only Tournaisian and uppermost Upper Visean were hitherto known (H. Żakowa, 1981). The tuffs were originally built of fine ash material of fine-aleuritic fraction, composed mainly of volcanic ash, some feldspars, pyrogenic quartz and, sometimes, biotite. Glass and feldspars were completely decayed and transformed into clay minerals which form an illitemontmorillonite-kaolinite mixture with admixtures of seladonite. Mineralogical and petrochemical character of this volcanic material appears fairly uniform, indicating acid volcanic source of the rhyolite type. The above described volcanic material and that known from the borehole Bolechowice IG 1 (W. Ryka, H. Żakowa, 1964) were presumably derived from a single source and in single eruption cycle. The tuffs do not display any significant terrigenous admixture and pyrogenic material – any traces of redeposition. A dependence of chemistry on size of tuffogenic material, found in analogical strata from the Gałęzice Syncline (K. Łydka, H. Żakowa, 1975), is not traceable here because of the above mentioned uniform character and size of pyrogenic material.