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Sedimentology of the Godula Formation in the Moravskoslezské Beskydy Mts. (Outer Western Carpathians, Czech Republic)

Maceček Lukáš

Annales Societatis Geologorum Poloniae

2021

Vol. 91, No. 3

309--325

The present account summarizes the results of lithological and facies analysis of representative sections of the Godula Formation, in order to contribute to the understanding of the lithofacies structure of this formation, the processes involved in its development and the character of the depositional environment. The sedimentology of different parts of the Godula Formation was investigated in six representative sections in the western and central parts of the Moravskoslezské Beskydy Mts. The Godula Formation is made up mainly of Upper Cretaceous siliciclastic turbidites and was formed during the most significant depositional phase of the filling of the deep-sea Silesian Basin. On the basis of sedimentological research, five facies classes (including four subclasses) were defined: 1) conglomeratic sandstones, 2) sandstones, 3) sandstones with mudstones, 4) mudstones with sandstones and siltstones, and 5) mudstones with siltstones. The methodology of facies analysis allowed the identification of several facies association, corresponding to the medial and distal parts of a turbidite fan and associated siliciclastic apron. The facies of depositional lobes, lobe transitions and the apron are described. The sandstone and mudstone facies (F3) occurs mostly in the depositional lobes. The sandstone facies (F2) and mudstone with sandstone and siltstone facies (F4) are present only to a lesser degree. The facies of the lobe transitions include lithologic associations of the lobe fringe and channel levee environments. They comprise mainly the mudstones with sandstones and siltstones (F4) and the mudstone with siltstone facies (F5). In the apron deposits, the sandstone facies (F2) and the conglomeratic sandstone facies (F1) predominate. Palaeocurrent analysis from measurements made in selected profiles showed that in the Moravskoslezské Beskydy Mts., the dominant direction of sediment transport was from SW to NE. After applying correction of the known counterclockwise rotation of the nappes of the Outer Carpathians, this corresponds to a longitudinal direction along the original axis of the basin.

Frequency of fast geomorphological processes in high-gradient streams: case study from the Moravskoslezské Beskydy Mts (Czech Republic) using dendrogeomorphic methods

Šilhán K.

Geochronometria

2012

Vol. 39, no. 2

122-132

High-gradient streams are localities with the most dynamic activity of geomorphological processes in medium-high mountains. This study of the frequency of floods and debris flows in a se-lected high-gradient stream in the Moravskoslezské Beskydy Mts was based on a dendrogeomorphic approach. It makes use of the most accurate methods applied in the dating of historic geomorphologi-cal processes. Individual events were reconstructed on the basis of the dating of various growth dis-turbances displayed in 99 samples taken from 56 predominantly broad-leaved trees. As for the studied area, 26 years out of the last 113 years have been identified as years of rapid geo-morphological processes. The frequency of the processes has been high above average since the 1970s. A majority of the events can be considered as flash floods. Debris flows, which can only be observed sporadically, originate due to the reactivation of old accumulation material that subsequent-ly ends up re-accumulated on the alluvial fan at the mouth of a stream. A large number of events oc-cur in connection with extreme short-term precipitation in summer months. In addition, they are af-fected by fast snow melting in spring, which has also been proved by intra-seasonal dating of selected events.