Przekrój geologiczny przez depresję północnosudecką

Abstract

GEOLOGICAL SECTION THROUGH THE NORTH-SUDETIC DEPRESSION

Summary

The geological section through the western part of the North-Sudetic depression has been worked out (Fig. 1). In the basement of the southern part of this unit are found Precambrian deposits, in the northern one - Silurian (Fig. 2). Among the formations filling in the depression, in the southern part are found Upper Carboniferous deposits (Stephanian). As concerns the Rotliegendes formations the first cycle coincides with the range of the Carboniferous strata (Fig. 2); the second one is developed in the southern part as sedimentary formations; and in the central part, as well as in the northern part - as volcanic and tutffaceous formations (Fig. 3). The third cycle, only of sedimentary nature, thickens from south to north, entering the Fore-Sudetic block. The Zechstein deposits are found along the whole section (Figs. 2, 4). They are developed in the basin and marginal facies. The Zechstein transgression reached far beyond the present-day outcrops, more to the south of the bore hole Żarska Wieś, than to the north of the bore hole Iłowa. The adjacent part of the Fore-Sudetic block was rather an emerged area, except for its near-edge portions characterized by varying width. The Lower and Middle Buntsandstein and the Cretaceous deposits are developed completely along the whole section, whereas the Roethian and the Muschelkalk - in the northern part only (Fig. 2). It results from the geological data that two stages of folding process can be distinguished in the basement of the depression: between the Precambrian and Cambrian, and after the Upper Silurian. On the other hand, within the infilling formations three phases of discontinuous deformations can be observed. These are related to the Variscan, Cimmerian and Saxonian movements. Tectonic processes are responsible for the present-day form of the North-Sudetic depression cut by relatively numerous dislocations.