Próg Pompeckiego i jego paleogeograficzne znaczenie dla polskiej jury

Abstract

POMPECKJS SWELL AND ITS PALAEOGEOGRAPHICAL IMPORTANCE FOR POLISH JURASSICSummaryAs a result of the examinations of Polish Jurassic made in the last 20 years, an attempt can be made to determine the extent of the Pompeckj's swell from the east, and to increase our knowledge as concerns this palaeogeographical element.So, the following statement can be added to those formulated by J. F. Pompeckj, A. Bentz, L. Riedl, O. Seitz, K. Hoffman and others.The Pompeckj swell is a palaeologeographical, and not a tectonical element. At the Mesozic time, the swell revealed an increased mobility, characterized by predominance of uplifting movements. The mobility was responsible for a considerable removal of Middle Jurassic deposits which, after reduction, were preserved only in morphological or tectonical depressions. The zone of the reduced Middle Jurassic deposits that stretches between Gotrzów Wielkopolski, Kalisz and Zawiercie, is the eastern boundary of the Pompeckj's swell. It can be ascertained here that the Upper Liassic deposits  are, as a rule, covered with the Upper Bajocian ones. The Laver Bajocian deposits with Sonninia sowerbyi (M i l l.) S o w., found near Zawiercie, represent the only known occurrence site of deposits that belong to this sub-stage. In the West-Pomeranian area the influence of this mobile swell is reflected in the form of huge thicknesses and of the “Cornbrash” facies in the Calliovian, the thickness of which is approximately 300 times greater than its average thickness observed in the remaining areas.In the Częstochowa ore-bearing clays, the influence of the swell can be investigated in the zone Parkinsonia schloenbachi in the form of an increased sand content.