Nowe dane o paleozoiku w podłożu Niecki Nidziańskiej

Abstract

NEW DATA ON THE PALAEOZOIC IN THE BASEMENT OF THE NIDA TROUGHSummaryAccording to the programme of deep structural drillings, bore hole Węgrzynów IG-1 (Fig. 1) was made in the years 1966-l967. Under the Quaternary (down to 7.0 m), Cretaceous (down 165.0 m), Jurassic (down to 718.0 m) and Triassic (down to 1058.6 m), the bore hole pierced the Lower Carboniferous formations (down to 1447.0 m) and entered the Devonian ones, penetrating to a depth of 3101.2 m. The Carboniferous formations (380.0 m in thickness) are represented by the Upper Visean (down to 1419.2 m) and the Lower Visean. Down to the depth of 1333.9 m, the Upper Visean deposits are built up of siltstones, claystones and sandstones with flora and microflora representatives (pointing to the uppermost part of the Upper Visean), and with fauna remains such as brachiopods, gastropods, pelecypods, cephalopods, coniconchs and fish spicules. Except for the first groups, the remaining ones comprise forms known to occur in the Upper Visean-Namurian assemblages. The presence of Sudeticeras cf. newtonense and S. cf. wilczeki-heferi points to the zone Goγ (Fig. 2). The underlying formations of the Upper Visean consist of conglomerates intercalated in their top portion with limestones; the fauna of the latter is represented by brachiopods and corals (guide forms of the zone D2-3). At the lower part, the conglomerates reveal limestones with unimportant fauna and conodonts of the zone Goniatites. The Lower Visean is characterized mainly by interfingering conglomerates and limestones that disclose rare fauna and conodonts, characteristic of the upper part of the zone Pericyclus. Within the Devonian formations, Famennian has been distinguished, built up of limestones and marls. From 1477.8 to 1551.5 m, it is evidenced by conodonts (to IIβ - to VI) and from 1546.5 to 1979.4 m - by brachiopods, pelecypods and trilobites. Disputable is here, however, the problem of the subdivision of the deposits found to occur at a depth of 1979.4-2523.0 m (limestones and dolomitic marls disclosing uninteresting fauna). These deposits are referred to the Upper Devonian, mainly due to the fact that amphipores occur beginning with a depth of 2523.0 m only. From that depth the deposits have been defined as those belonging to Middle Devonian. Givetian, represented here by dolomites and dolomitic marls, occurs at a depth of 3014.8 m. Its boundary with Eifelian (dolomites, claystones, dolomitic limestones and anhydrites) has been determined on the basis of certain differences in lithology only (Fig. 2). The Devonian formations are thick (really up to 1518.0 m in thickness). Most probably, they have been laid down in a narrow, NW-SE trending graben, distinctly lowered at the Upper Devonian time. Of considerable importance is here the zone Cheiloceras, whereas the upper zones of the Famennian are thick up to several ten metres only. Gap that comprises also Tournaisian suggests the uplifting of the area near Węgrzynów. New sedimentary cycle began in the Lower Visean; the presence of the conglomerates proves an intensity of the diastrophic processes within the neighbouring area. Some limestone banks with benthonic fauna in the Upper Visean correspond, however, to a periodical stabilization of sedimentary conditions. The article also points to an analogy in the development of the Famennian and Upper Visean of the Węgrzynów area and that of the south-western part of the Świętokrzyskie Mountains, as well as to a similarity between the diastrophic-sedimentary cycle that has taken place in the Carbonioferous of the area of Węgrzynów, and of the zone Łobzów-Słomniki (Fig. 1). It is emphasized in the article that within the Nida trough, epeirogenic movements took place at the Devonian and Carboniferous times, causing a displacement of continents and seas, some changes in the depth of transgression areas and in the thickness of the deposits, as well as an inflow of coarse-grained material and certain changes in morphology of the basin bottoms. The pre-Permian structure is of a block-fold nature (Figs. 1 and 3), this being evidenced by a stratigraphical differentiation of beds within small areas, by their gentle dips, and by small disjunctive deformations. Distinct were here vertical forces that, for the most part, rejuvenated both Caledonian and older tectonical frameworks. The Caledonian and the older structures are characterized by an almost W-E direction, whereas the Variscan ones - by NW-SE directions.