Zarys stratygrafii i tektoniki południowej części niecki łódzkiej (rejon Bełchatowa)

Abstract

OUTLINE OF STRATIGRAPHY AND TECTONICS OF THE FORMATIONS IN THE SOUTHERN PART OF THE ŁÓDŹ TROUGH (Bełchatów region)SummaryThe article deals with the stratigraphy of the sub-Cainozoic formations and presents a conception concerning the tectonical structure of the southern part of the Łódź trough. Both comparison and interpretation of all materials available allowed the present authors to plot an uncovered map of Mesozoic formations. Owing to a complicated geological structure, and due to the scarcity of data the geological picture of the region in study is, of necessity, presented in an outline only, and the tectonics, is, as a rule, shown in general lines (Fig. 1). A detailed stratigraphical analysis of the geological materials from the Bełchatów region allows, in many cases, to ascertain the presence of a series of tectonical elements.However, due to the large scale of the map published, certain dislocations cannot be plotted on it.Here, a series of Laramie anticlines and synclines can be observed, characterized by a general NW –SE direction of their axes. They are disturbed by at least two generations of dislocations. The first generation of these dislocations, corresponding in age to the anticlines and syncines, reveals NW–SE and NE–SW directions.The second generation, Alpine in age, characterized by a W–E direction, determines the role of graben.Bore hole Dębina demonstrates that under the Cainozoic formations, gypsums and anhydrites occur at a depth of about 90 metres, overlying mixed Cretaceous and Upper Jurtassic deposits. These in turn rest on a series of Zechstein anhydrites pierced to a depth of 30 m only. According to Z. Dąbrowska (1967), this is probably a small "chimney-like" salt dome. Plastic Zechstein deposits of saline facies probably underlie the whole graben filled in with brown coal formations.The following are deposits distinguished within the Jurassic formations: Lower Jurassic deposits that consist of Olewin, Wieluń, and Ciechocinek series; Middle Jurassic deposits with Kuiavian, Bathonian and Cahlovian; Upper Jurassic deposits with Middle Oxfordian (in part), as well as Upper Oxfordian, Kimmeridgian and Portlandian in the north-eastern part of the area in study.The Cretaceous in this area is represented mainly by deposits from Albian to Maestrichtian inclusive. The Lower Cretaceous deposits are found only in the north-eastern part of the area, i.e. in the Tomaszów trough.