Paleotektonika basenu permu na Niżu Polskim

Abstract

 Dokonano analizy paleotektonicznej poszczególnych etapów rozwojowych permu oraz sumarycznie całego tego okresu, wprowadzając metodę oceny trwałości wypiętrzeń i obniżeń. W basenie wyróżniono bruzdę centralną o maksymalnej subsydencji, najczęściej kompensowanej przez sedymentację. Bruzda ta, powstała być może na założeniach waryscyjskiego rowu przedgórskiego, ograniczona była od NE zdecydowanie stabilnym obszarem starej platformy, a od SW mniej sztywnym obszarem przedsudeckim, nałożonym na zewnętrzną strefę pasma waryscyjskiego. Rozwój basenu był zależny od kilku kierunków tektonicznych: NW – SE, WNW – ESE i N – S. Rozpatrzono problem dziedziczenia permskich tendencji paleotektonicznych w mezozoiku.

PALAEOTECTONICS OF THE PERMIAN BASIN IN THE POLISH LOWLANDS

Lithofacies and palaeogeographic maps of the succesive Permian evolutionary stages except for the Lower Rotliegendes (Atlas litofacjalno-paleogeograficzny ... , 1978) have been interpreted in terms of the palaeotectonic, down-warped and up-warped units (Figs. 1 – 5). On this basis two compound maps have been then prepared (Figs. 6 and 7), showing the persistence of palaeotectonic elements throughout the Permian period. These elements owe their origin to the Late Variscan faulting and warping processes.

Arcuated structures in the Fore-Sudetic area (Wolsztyn Uplift, Zielona Góra Depression) were probably inherited from the morphological-tectonic units of the Rheno-Hercynian Zone of the Variscan orogen. Some features are there oblique or perpendicular to the main trends (Poznań and Laskowice Grabens), being the result of the activity of transverse faults. With the passage of time the uplifted elements were being gradually segmented, subsided and submerged by the Zechstein sea. This process came to an end by the time of the PZ3 cycle. Nevertheless, a palaeotectonic- palaeomorphological edge existed constantly during the Zechstein in the southernmost part of the area.

On the opposite side of the basin, within the territory of the old East-European Platform, the then existing elevated blocks Cuba Uplift, Mazury Uplift) persisted all the time, their extent even gradually growing. This unit as a whole was distinctly more stable than the Variscan belt. Its southwestern boundary follows strictly the outer edge of the Platform delimited by the seismic refraction data. Adjacent to this edge in its northwestern part, the Kamień–Chojnice Zone, where the Permian rocks are underlain by the strongly block-faulted Devonian and Carboniferous strata, distinguishes itself by its conspicuous mobility.

Between the above-mentioned major palaeotectonic units, the Central Furrow developed presumably at the place of the Sub-Variscan fore-deep. It is marked during the whole time-span discussed by the considerable subsidence, partly non-compensated by the accumulation of sediments.

Some principal palaeotectonic trends can be recognized within the Permian basin. They are:

NW-SE trend, roughly parallel to the boundary of the East-European Platform; WNW-ESE trend (so called “Góry Świętokrzyskie Mountains trend”), clearly visible both in the southern part of the Fore-Sudetic area as in the Kamień–Chojnice Zone, representing probably older (Caledonian?) trends, rejuvenated during the Variscan tectonic epoch; finally, submeridional trends of obscure origin.

Many of the Permian palaeotectonic units have also been observed in the Mesozoic sequences.

These are presented in Fig. 8 which is prepared in a somewhat different manner than the remaining maps.