Geological structure of the western part of the Polish Carpathians

Abstract

The study area is located between Cieszyn and meridian of Sucha Beskidzka. The Precambrian and its cover - Palaeozoic platform deposits - occurring here, are strongly deformed and capped by the Neogene molasse. The major part of the area is occupied by the Flysh Carpathians. In the Carpathians, units of the Middle Group (Skole, Sub-Silesian, Klippen, Silesian, Dukla and Grybów) as well as the Magura unit have been distinguished and described.Geological structure of the lower structural stages have only been outlined while the flysch, its stratigraphy and tectonics, has been discussed in details. The Sokole unit occurs in the marginal part of the Carpathians, in the region of Andrychów and in tectonic windows within the Sub-Silesian and Silesian units. Deposits of the Sub-Silesian unit are found at the surface as two or three discontinuous bands. During the Neogene the unit had been truncated and developed as doubled or even tripled scales (imbricated folds). The most external part of the Sub-Silesian unit occurs at the front of the Carpathian overthrust as a band extending from Cieszyn to the region of Andrychów. The more internal part or the unit is recorded in the Dzięgielów and Ustroń windows, and the innermost, southern part is found at the front of the Dukla, Grybów and Magura units. The middle element of the Sub-Silesian unit might be associated with the extension of the Lanckorona-Żegocina zone towards the west. The Silesian unit is divided into tectonic sub-units: the lower one - Cieszyn sub-unit (nappe), and the upper - Godula sub-unit (nappe). Detachment which lead to separation of the Godula sub-unit as a separate entity took place within the Upper Cieszyn Shales or slightly higher. The Dukla unit sensu lato has been distinguished between Ślemień and Istebna. In the eastern part, between Ślemień and Żywiec, the Dukla unit is thrust over the deposits of the Silesian unit of the Little Beskid block. In the southern part of the Żywiec Basin the discussed unit together with the deposits of the upper Grybów unit is thrust over the deposits of the Cieszyn Silesian sub-unit. South of Barania Góra Mt. the Dukla unit is thrust over the deposits or the Silesian Beskid.The authors distinguish the deposits of the Grybów unit between Gilowice and Istebna region. The unit is mainly formed by clayey-marly deposits of the Lower Cretaceus-Palaeogene age. This unit was strongly compressed, scaled and crushed between the Dukla and Magura units. In exposures, the Grybów unit takes a form of isolated scales and tectonic caps. It has also been identified in numerous tectonic windows within the Magura unit. The Magura unit is the highest unit in the discussed region. It is subdivided into three sub-units. The northern one is the Siary sub-unit and its deposits are thrust over the units of the Middle Group. The middle one is Racza sub-unit over which the southern one - Bystrica sub-unit - is thrust.