Makro- i mikrofauna oraz petrografia famenu z otworu wiertniczego Kowala 1

Abstract

Opisano towarzyszące zespołom konodontowyrn i sporowym szczątki organiczne - ramienionogi, małże (najliczniejsze), głowonogi, otwornice zlepieńcowate oraz bentoniczne i planktoniczne małżoraczki. Korelacja wyników badań biostratygraficznych sugeruje niewielkie luki w zonacji wyższej części profilu famenu i kondensacją stratygraficzną osadów graniczących z franem i turnejem. Scharakteryzowano petrograficznie i genetycznie osady gruzłowe wyróżniając w nich deformacje plastyczne, sztywne i tektoniczne. Na podstawie cech mikro- i makroskopowych oraz chemizmu osadów skonstruowano profil petrograficzny osadów famenu.

Macro- and microfauna and petrography of the Famennian deposits in the Kowala 1 borehole

The macrofauna is represented by (Tables I - III) brachiopods, molluscs and fragments of crinoids accumulated in thin layers at depth 202.0- 230.0 m (Fig. 1). Brachiopods are represented by Inarticulata (numerous) and Articulata. Among the former there are Orbiculoidea kadzielniensis Biernat as well as specimens belonging to the Lingulidae family. There are also representatives of four orders of Articulata namely Orthida, Strophomenida, Rhynchonellida and Spiriferida. Out of the molluscs there are Nautiloidea, Cheiloceratidae, Platyclymenia? sp., one specimen of Cypricardinia? sp., and dominant Guerichia classified for the time being as Bivalvia. Those fossils are abundant in intercalations of bituminous shales in two highest lithostratigraphic complexes of the Famennian (A. Romanek, M. Rup, 1990). With the exception of Guerichia venustiformis (Sadykov) the other taxons are characteristic for the Famennian. J. Malec has obtained about 200 specimens of arenaceous foraminifers and some hundreds of ostracods. The foraminifera belong to 6 genera. Among the ostracods benthonic Entomozoida (numerous) and planktonic once have been encountered. Richterina (Maternella) dichotoma (Paeckelmann) and R. (R.) costata (Richter) point to the hemisphaerica-dichotoma Zone in the interval 16.3-42.7 m. The benthonic ostracods belong to 10 genera and 10 species or forms similar to species and are to be found mainly at depth 11.0 m. All the taxons except of Healdia ratra Griindel have been already described from Kowala (E. Olempska, 1979) as well as the planktonic ostracods. The correlation of biostratigraphic results points to a non-disturbed Famennian profile which exceeds 200 m in thickness and belongs to the southern facies zone of this stage in the Holy Cross Mts. Presence of the postera Zone is still an open question in the light of various dating of sediments in the interval 22.1-42.7 m (M. Nehring-Lefeld, 1990; E. Turnau, 1990). The rhoniboidea Zone is not documented by conodonts which may be explained by existence there of marls and laminated limestones. Deposition during Famennian times had taken place in a pelagic basin (some hundred metres deep) characterized by weak bottom currents and occasional storms. The environment must have been euxenic one with occasional inflow of more oxygenated water (e.g. the lower complex with benthos). There were also bathymetric pulsations, periodical strong reduction conditions (bituminous claystones), higher subsidence in the Lower Famennian, stratigraphic condensation near the Frasnian-Famennian and Famennian-Tournaisian boundaries. Platy, lense-like and nodular sediments have been distinguished in the Famennian profile (Fig. 3). The latter the authors regard to be a result od deformation of the platy sediments being in semifliquid state, plastic or rigid (under strain) and "frozen" in various stage (Fig. 2). They were displaced in result of sediment gravity flows, bottom currents as well as storms. The early diagenetic structures were then superimposed by secondary ones associated with processes of rupturing and dia- and epigenetic boudinage. On the basis of petrographic features (Tables IV-VI) as well as quantitative and qualitative similarities of perallochems in the nodules and surrounding matrix an attempt has been undertaken to define the all ower autochtonism of the nodules, of their development duringsedimentation and diagenesis. The nodules have been classified to the allochtonous detrital deposits as well as to the chemogenic ones and to the mixed ones (of both characters). Radiolarians have played an important role in the origin of the sediments in which metasomatic calcitisation had followed the formation of the nodules. Presence of radiolarians, locally of quartz and biotite points to the fact that volcanic ash has entered the basin in form of pelite. Its decay led to high silica concentration in marine water. Concurrence of radiolarians and inarticulate brachiopods is interpreted as result of storm deposition.