Budowa Geologiczna strefy żegocińskiej

Abstract

GEOLOGY OF THE ŻEGOCINA ZONE (WESTERN FLYSCH CARPATHlANS)

The Żegocina zone is the easternmost part of an elongated zone of tectonic windows which stretches from Rajbrot to Żywiec in the Silesian nappe of the Western Carpathians. In the north the Żegocina zone borders on the Czchów anticline, a tectonic element of the Silesian nappe, while in the south and east it is bounded by the Magura nappe. Upper Cretaceous and Palaeogene deposits of the Sub-Silesian nappe, as well as Lower Cretaceous rocks of the Silesian nappe, build the geology of the Żegocina zone. Upper Cretaceous beds of the Sub-Silesian series consist of three distinct facies which may be regarded as stratigraphic members. These facies are: a) grey marls with exotics, b) variegated marls with Żegocina marls, c) glauconitic sandstones from Rajbrot as well as sandstones and conglomerates from Rybie. In the Upper Cretaceous different diastrophic phenomena occurred in the sedimentation basin of the Żegocina zone, such as the emergence of an island, accompanying volcanic disturbances, etc. These processes constitute a stage directly followed by Laramide orogeny. Two main dislocation zones embracing the southern limb of the Czchów anticline were formed after the overthrusting of the Silesian nappe onto the Sub-Silesian unit. The longitudinal Żegocina dislocation stretches somewhat obliquely to the axis of that anticline. The transversal dislocation of Rajbrot covered by the Magura nappe has a north-south direction. Along these faults the western part of the southern limb of the Czchów anticline has been considerably uplifted in relation to the eastern part. Tortonian erosion processes denuded the younger rocks of the Silesian series in the uplifted area down Lower Cretaceous strata, locally even stripping off those of the Sub-Silesian series. Tortonian sediments occurring at Żegocina (Opolian substage?) were deposited on the eroded surface of the Żegocina zone to be subsequently subjected to simultaneous folding.