Problemy tektoniki i morfologii stropu mezozoiku między Bełchatowem a Działoszynem

Abstract

TECTONICAL AND MORPHOLOGICAL PROBLEMS OF THE MESOZOIC TOP BETWEEN BEŁCHATÓW AND DZIAŁOSZYNSummaryLithology and tectonics of Jurassic and Cretaceus have been the main factors affecting the development of the Mesozoic top strata in the region under consideration.Jurassic deposits occur in the south-western, part of the area (Fig. 2 and 3) and Cretaceous which are found within both the Nida and Łódź troughs, occupy eastern part.In the south-eastern and middle parts, the deposits found, at the top of the Substratum, in the form of tectonical horsts. Tectonics of the area in study has been influenced by the Variscan tectonics of the adjacent Świętokrzyskie Mts. the north-western continuation of which can probably be observed in the Mesozoic formations.The most considerable influence has, however, been exerted by the movements related to tectonics. These are responsible for production of main faults and tectonical features of SE–NW and SW–NE directions, as well as, for the formation of horsts at Łękińsk, Kodrąb and Rzejowice.At the Tortonian time, tensional movements produced, after the formation of the main Middle-Alpine folds, a series of and tectonical subsidences within the Carpathian foreland, and gave rise to the formation of the Kleszczów graben. The vertical development of this graben was characterized by three phases that took place at the Miocene time. During the oldest phase, the subsidence was violent, and the graben constituted a limnic water basin. The second phase was related to the formation of peat bog, thus to a higly slow lowering movement. The third phase was again characterized by fairly violent movements followed in turn by slow movements and  interruptions. At that time, the area of the graben again became a water basin, in which sandy, peaty, and clayey deposits were laid down.The Pleistoctene time was also characterized by a slow bottom subsidence of the Kleszczów graben. This is proved by the preserved sediments of almost all the glaciations and interglacials known to occur in this area of Poland.In general, the Mesozoic surface of the Bełchatów area represents a trough-like form characterized by absolute heights from 220 m in the south up to 160 m in the north (Fig. 1) . Above this surface there appear some flat humps, particularly in the southern part of the area. Among negative forms are found tectonical fractures and erosional valleys incised into the Mesozoic formations.The erosional valleys depend either upon the direction of main fractures (NW-SE and NE-SW) or upon the Lower resistance of Albian rocks against denudation factors (sands and sandstones). Here belong valleys eroded within the fault zones along the lines Szczerców-Widawa and Prusiecko-Dubidze. The deepest valleys were formed, however, along the lines of tectonical fissures, on which karst phenomena can be observed. In certain areas, e.g. along the line Osieczno-Broszęcin, and in the region of Siemkowice, the karst processes were responsible for almost complete destruction of calcareous rocks, Upper Jurassic in age. As a result of this activity, valleys were formed more than 100 m in relative height, where Quaternary formations were laid down immediately on the Middle Jurassic deposits (Figs. 2 and 4).