Zarys stratygrafii cechsztynu niecki północnosudeckiej

Abstract

Przedstawiono nowy schemat korelacji stratygraficznej cechsztynu niecki północnosudeckiej.Omówiono wykształcenie cechsztynu w poszczególnych rejonach niecki i stwierdzono, że w jej północnej części występują osady werry, stassfurtu, leine i alleru, natomiast w południowej – tylko werry i leine. Wyniki badań pozwoliły na reinterpretację paleogeografii cechsztynu północnosudeckiego. OUTLINE OF THE ZECHSTEIN STRATIGRAPHY IN THE NORTH SUDETIC TROUGH The Zechstein deposits in the North Sudetic trough (Fig. 1) are characterized by the incomplete development of cyclothems and by important amount of the clastic deposits (Table 1, Fig. 2-8). That is why the problem of the North Sudetic Zechstein stratigraphy is a matter of controversies (Table 1, Fig. 3). Results of the research in the Wrocław region (T. M. Peryt, 1977) and the earlier reinterpretation of the Zechstein stratigraphy in western part of the North Sudetic trough allow to verify the stratigraphy and to correlate the North Sudetic Zechstein with that from the central part of the Zechstein basin.First of all, the clastic-sulphate series (in the northern and central parts of the trough) and the clastic one, (in the central part) occuring above the Zechstein Limestone (Ca1) and below the Platy Dolomite (Ca3) are included to the Werra (Table 1, Fig. 2-8). It should be stressed that it is a simplification as by analogy with the situation observed in the Wroclaw region the clastic development of the Stassfurt can be expected, however, in great majority of cases any reasons allowing to separate the clastic Stassfurt are lacking, The clastic deposits above the Platy Dolomite were included in the Buntsandstein (Table 1, Fig. 3-8) after J. Mroczkowski (1972).The lithological development in parts of the North Sudetic trough (Fig. 2-8) is discussed and the outline of paleogeographical evolution of studied region is presented. The Werra basin was of the greatest extent (Fig. 9), the extent of Leine basin was slightly smaller (Fig. 11) while the Stassfurt extent was considerably smaller (Fig. 10). The Zechstein Limestone in the North Sudetic trough is of evidently regressive character like in other parts of the Zechstein basin. Continuous shallowing led at last to subaerial exposure of the nearshore area of sea at least on the area of North trough; it caused the end of carbonate sedimentation and the start of clastic sedimentation – sandstones originated near the shore While clays tones basinward. The Werra anhydrites originated in more central part of the basin contemporaneously with the clastic deposits of the nearshore part. Quite considerable moving of the Werra anhydrites extent in the northward direction in comparison with the Zechstein Limestone extent was the result of sea diminishing.Further migration of the coast line in the northward direction took place in the Stassfurt (Fig. 10). In the Stassfurt basin the deposits of the Main Dolomite and later of the Basal Anhydrite and also of the Older Rock Salt in places originated. In the Leine the coast line moved considerably southward (Fig. 11); near the shore the Platy Dolomite deposits while north of Węgliniec the Grey Pelite and the Main Anhydrite deposits accumulated.