An attempt to evaluate denudation size of homoclinal flysch ridge basing on reconstruction of long-lasting relief development (hypothesis, facts, interpretations). Case study of Mt. Babia Góra (1725), Western Carpathians

Abstract

The homoclinal ridge of Mt. Babia Góra (1725 m a.s.l.) is the highest flysch ridge in the Western Carpathians. Denivelations within the ridge exceed 1000 m. It is built of resistant Magura sandstone overlying less resistant sandstones and shales. The layers of Magura sandstone dip to the south. The ridge is formed as a huge cuesta with north precipitous escarpment slope and south gentle penestructural slope. The researched relief and geological structure of the ridge and its surrounding make it possible to reconstruct long-lasting relief development since the Upper Miocene.The Author took account of predominated in the 20th century view concerning intensive denudation in the Flysch Carpathians since the Upper Miocene and also the view of periodic relief development, which was connected with climate changes and changes in the intensity of tectonic uplift movements (alternate uplifting and stabilisation of the area studied). In relations to these views, the Author considered also recently endorsing view assuming permanent trend in uplifting movements (with decreasing intensity) in the Polish Flysch Carpathians, and also indicating that terrain depressions are not result of denudation but local submering movements. This analysis took also account of differentiation of modern uplifting movements.In the relief of the ridge studied and its surrounding traces of four geomorphological levels (not planation surfaces!) of different age are visible. The may be interpreted as traces of periodical uplifting which started in the Upper Miocene, valley deepening, slope retreat and development of pediments in the Upper Neogene and Quaternary. Taking into account modern limit of Magura sandstone spreads (which to cover the whole area in the Upper Miocene) and distribution of traces of former geomorphological levels, it is possible to evaluate the presumed thickness of these sandstone layers and underlying older flysch sediments which became denudated due to landslide movements on slopes and alluvium dischargein river channels.A large-scale occurrence of landslide movements sine the Upper Miocene on slopes of Mt. Babia Góra are indicated by mélange structures visible in stream channels and also large slumped rock packages creating isolated hills at the ridge foot. Denudation of Mt. Babia Góra ridge has been more intensive on the escarpment slope where concentric pattern of river system has caused larger drainage outside, whereas on the southern slope divergent pattern of river system dominates. Another reason of smaller denudation on the southern slope of the ridge is its relief – penestructural slope is more resistant to denudation than the escarpment slope.Estimating evaluation of the denudation size of Mt. Babia Góra ridge was related to the views mentioned above indicating on hypotheses, facts and interpretations.