Rozwój litologiczno-paleogeograficzny dewonu i dolnego karbonu w Niecce Nidziańskiej

Abstract

LITHOLOGIC-PALAEOGEOGRAPHIC DEVELOPMENT OF THE DEVONIAN AND LOWER CARBONIFEROUS IN THE NIDA TROUGHSummaryThe problem has been elaborated on the basis of the materials obtained from deep drillings and geophysical surveys, carried out within the area considered, by the Geological Institutes Branch of the Świętokrzyskie Mts. in Kielce and by Petroleum Industry. This allowed the authors to compile a fairly detailed geological map of the sub-Permian basement (Fig. 1) in relation to the Palaeozoic of the Świetokrzyskie Mountains, to analyse the results of drillings made in the western margin of this latter, and to interpret the sub-Mesozoic structure of the northern margin.Within the orogenic massif of the substratum of the Nida trough are found the following structural stages: Małopolska stage (Late Proterozoic), Sandomierz stage (only the lower part represented by Vendian), and Young Caledonian (Ordovician, Silurian) stage. The last stage is preserved only in some depression areas of this massif. The Caledonian megacycle ended at the close of the Silurian, both within the trough here considered and within the Silesian-Cracow area, with molasse deposits resembling conglomerates from Łapczyca, Wyciąża, Mikluszowice, and Jaronowice.The Epi-Caledonian covering stage was formed during the Variscan-Alpine sedimentary-diastr,ophic megacycle. The present paper deals with the fragment of this stage only, concerning the Variscan super-complex that comprises the Devonian and Lower Carboniferous deposits, in the case of Milianów, Słomniki, Marszowice and Zielona – also the bottom part of the Namurian ones. The development of the Syn-Variscan cycle has been comprehensively presented on the maps made for the individual stages (Figs. 2–9). Evidence materials, initial for the construction of these maps, concerning the subdivision of the Devonian and Carboniferlous, are given in Table 1, according to the published papers and archival data.The development of the sedimentation of the Variscan super-complex was conditioned by the morphological differentiation after the Young Caledonian movements and the pre-Devonian denudation. During the sedimentation of the Devonian and Carboniferous deposits active were the basement uplifts of Precambrian age along the lines: Skała–Wyciąże–Puszcza; Opatkowice–Książ Wielki–Żarnowiec; and Chmielnik–Jędrzejów. In the depressions between them more continuous deposits were laid down not only of the Caledonian megacycle, but also of the Variscan-Alpine one. The development of the Variscan cycle was strongly affected by the transversal elevation Miechów–Książ Wielki–Chomentów. In different periods this elevation, according to the intensity of the movements – mainly of epigenetic nature – may have impeded the contact of the basins found on its either side (e.g. in the Famennian, the early Lower Carboniferous), have decided the development of lithofacies and biofacies in a north-western or south-eastern direction (both in the Devonian and the Carboniferous), and have, in its vicinity, determined considerably the formation of depression zones presented an the maps and discussed in the Polish text. It is assumed that marine facies developed on this elevation (e.g. in the Middle Devonian and in the Lower Visean) were of a shallow-water nature, characterized by reduced thicknesses of the deposits.Discussing the development of the Devonian and Lower Carboniferous the present authors emphasize the most important, in their opinion, geological phenomena, e.g. lithologic-facial changes, thicknesses, role of alimentation areas, changes in the extents of inundations in the individual stages, situation of depression zones and of increased subsidence, as well as tectonic activity. The present-day picture of the occurrence of the Palaeozoic formations was considerably affected by the Bretonian movements, as well as by the post-Visean and pre-Zechstein ones. The activity of the former is proved by the occurrence of different Visean members on either Frasnian or Famennian (e.g. Pągów IG-l, Słomniki IG-l, Strożyska 5), and by the occurrence of the Lower Tournaisian members on either Famennian or Frasnsian (e.g. Węgrzynów IG-l), as well as by some stratigraphical gaps within the Upper Devonian (e.g. Załucze 1). It is possible to distinguish here more stable zones characterized by the lower intensity of erosional processes, and teconically active zones resulting in an increased post-Visean degradation process. The latter zones run along the present-day uplifts of Precambrian age.