Uwagi o rozwoju molasy rowu przedgórskiego Karpat na Śląsku Cieszyńskim

Abstract

SOME REMARKS ON DEVELOPMENT OF MOLASSE IN CARPATHIAN FOREDEEP IN THE CIESZYN SILESIA Summary In the Cieszyn Silesia, the Carpathian Foredeep is infilled with Miocene molasse strata, assigned to the following lithostratigraphic units: Zebrzydowice, Dębowiec and Skawina formations. The basement of molasses is built of Paleozoic rocks of the Upper Silesian Coal Basin, covered with regolith. The regolith is developed as breccias and mottled conglomerates up to some tens meters thick and assigned to the Kłodnice Formation, diachroneous in relation to Miocene molasses. The first stage in infilling of the Foredeep was connected with sedimentation of claystones of the Zebrzydowice Formation, found in the deepest, axial zones of paleovalleys (Fig. 1). These sediments are correlable with gray and brown beds of the Carpathian in Moravia and they represent littoral facies of Early Miocene basin. The most complete sequences of this basin are known from the Sucha area and eastern parts of the Foredeep. Regression of that sea has presumably taken place in the Carpathian, at which time are dated erosion and sedimentation of continental breccias and conglomerates of the Kłodnice Formation. The second stage in infilling of the Foredeep is marked by cyclic sedimentation of Lower Badenian strata. In the Skoczów paleovalley, the cycle began with deposition of olistostrome built of rocks of Carpathian Subsilesian unit, Paleozoic exotics and Lower Miocene claystones. On slopes of the Cieszyn paleoelevation, slides were replaced by debris flows with olistoliths and boulders, passing upwards into gravels and sandstones. All the rocks form the Dębowiec Formation, infilling paleovalleys up to the level of about 100-130 m. Regressive sedimentation is closed by mudstones and claystones of the Skawina Formation, up to 1000 m in thickness. In the south, the formation contacts translocated Carpathian nappes, and in the north of the Pawłowice crest - salinary sediments of the Wieliczka Formation which end this cycle. The origin of Lower Miocene molasse is mainly due to destruction of the Carpathians uplifted in the Saavian phase whereas the Lower Badenian one developed in result of epeirogenesis and translocations of the Carpathians in the Early Styrian phase.