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THE GEOMORPHOLOGICAL DEVELOPMENT OF THE EASTERN PART

OF THE MIECHÓW PLATEAU

S u m m a r y

In this work, based on a geomorphological survice on a scalę of 1 :25000, the author reports upon the development and the conditions of relief development of the eastern part of the Miechów Plateau, which is located on the confines of two big morphological regions: the Cracow - Częstochowa Plateau and the Nida Trough. The area investigated is aiso situated on the peripheries of two large tectonic units: the Silesia — Cracow monocline and the Nida syncłinorium. This area is built of resistant Upper Cretaceous marł covered with smali patches of Lower Tortonian deposits. They consist of sands and argils of a smali resistance and medium resistant marls and gypsum. The Pleistocene sediments are com-posed of fluvioglacial sands (Vorschiittungssande), sandy morainic clay belonging to the Cracovaan glaciation (Mindel), river sands deposited during the two younger glaciations of Poland, and loess which corresponds with the Baltic glaciation (Wurm). The Holocene sediments consist of argillaceous river outwash.

The area investigated is conform to the Działoszyce syncline. In the west in the vicinity of Miechów it reaches Cretaceous elevations. The Cretaceous rocks form a slab. To the south and south-east they are plunging beneath Miocene sediments, which are lying morę or less horizontal. The Cretaceous formations have been cut by grabens („padoły") running from WNW to ESE and by a dense network of diaclases. The tectonic trends N-S, N 15°—35°E and N 60°—70°W are predominant. In the region investigated the directions of morphological forms are obviously corresponding to the oftenest returning trends of bedrock (N 60°—70°W) — fig. 6.

The sculpture of the Cretaceous substratum is varied. The occurence of Miocene sediments both on the tops of elevations and within the depressions carved in bedrock suggests, that the main features of relief of the area investigated have been formed during a long cycle of development including the period between the regression of the Upper Cretaceous sea from the Miechów Plateau and the inundation of the Lower Tortonian sea. The fragments of a surface of planation observed at an altitude of 310 to 360 metres (fig. 7) are considered to be the oldest element of the pre-Tortonian relief. This surface was produced under the conditions of a warm humid climate of the Eocene. At that time lively denuding processes almost com-pletely graded the region of the Miechów Plateau. In this surface of planation (pro-bably during the Middle Oligocene epeirogenic movements) valleys have been cut, running in a direction from WNW do ESE. After the Eocene-epoch but prior to the Lower Tortonian "padoły” have been formed too. Their origin is due to the orogenesis of the Carpathians. The net of pre-Tortonian valleys does not correspond to the direction and locality of the „padoły" and therefore it is older than the latter.