Uwagi o osadach cechsztyńskich w depresji śródsudeckiej

Abstract

 W zestawieniu wybranych cech klastyczno-węglanowych osadów cechsztynu w depresji śródsudeckiej zaznacza się istotne zróżnicowanie między osadami z okolic Chełmska Śl. i Kochanowa a osadami z okolic Radkowa. Niezbędne jest zrewidowanie dotychczasowych ustaleń dotyczących określania zasięgu osadów cechsztynu w depresji śródsudeckiej. Jedynie osady z okolic Chełmska Śl. i Kochanowa można określić jako cechsztyńskie. Osady z Radkowa należałoby traktować jako utwory reprezentujące najwyższe poziomy dolnego permu w depresji śródsudeckiej. Osady wykształcone w sposób zbliżony do osadów z okolic Radkowa zostały określone w depresji północnosudeckiej jako najwyższy czerwony spągowiec. SOME REMARKS ON THE ZECHSTEIN IN THE CENTRAL-SUDETIC DEPRESSION The lack of paleontological record makes it still necessary to use the presence of carbonate cement as one of the major criteria in identification of Zechstein rocks in the Central-Sudetic Depression (Fig. 1).The studies on thin carbonate laminae sometimes found in sandstone layers (Figs. 3, 4) and on rocks rich in clastic material (Figs. 5–7) showed marked differentiation in lithology of rocks from north-western (Chełmsko Śl., Kochanów) and south-eastern (Radków) regions. The differentiation was further supported by results of planimetric analysis (Table 1, Fig. 8) and comparisons of selected properties of clastic-carbonate rocks (Table 2). The obtained results may be interpreted in two ways:1. The rocks are isochroneous but related to different sedimentary environments. In the north-western (Chełmsko Śl., Kochanów) region, the sedimentation proceeded in shallow, nearshore zones of the Zechstein marine basin, under conditions of significant supply of terrigenous material from shore areas, and in the south-eastern (Radków) region – under continental conditions, due to debris flows accompanied by caliche accumulation. The southern extent of rocks of the north-western region may be, therefore, treated as southern boundary of Zechstein deposits in the Sudety Mts, whereas rocks encountered SE of that boundary should be treated as continental Upper Permian – Thuringian.2. The rocks are heterochroneous, referable to the Zechstein and uppermost horizons of the Rotliegendes and to different sedimentary environments. Similarly as above, the rocks occurring in the north-western region should be treated as delineating southern boundary of the Zechstein in the Sudety Mts, whereas clastic-carbonate rocks from the Radków area would represent the Rotliegendes subjected to caliche-forming processes. Rocks from the North-Sudetic Depression, resembling those from the vicinities of Radków in development, seem to occupy identical position as the latter (uppermost Rotliegendes – see J. Mroczkowski, C. Skowronek, 1980).The above data suggest the necessity to revise previous interpretations of the extent of Zechstein rocks in the Central-Sudetic Depression. It appears that only rocks from the Chełmsko Śl. – Kochanów region may be regarded as the Zechstein.