Cechsztyn w rejonie Gubina

Jerzy Milewicz




The basement in invaded by the Zechstein sea was for the most part base-levelled. A thin layer of copper-bearing shale, wide-spread throughout the area here considered, may prove such an opinion. The Zechstein sea was situated within the hot climate zone. Atmospheric precipitations were inconsiderable and irregular, thus being responsible for the negative water balance of the sea. This led to a long-lasting sedimentation of evaporates, supported by the subsidence of the basement. The subsidence in the region of Gubin reached its maximum in the Werra cyclothem, and its minimum at the time of the Aller cyclothem. It results from the maps of the maximum thicknesses that the most considerable subsidence of the basement was in the region of Brzozów - Sękowice - Witaszkowo. Apart from this, the subsiding areas changed their position during various cyclothems, depending upon the intensity of the subsiding processes. For example, the isopachytes of salts in the Stassfurt cyclothem prove the existence of an elevation in the site of previous depression, and the existence of a depression where an elevation was previously situated (Werra cyclothem). On the other hand, the character of the contour lines of salt thickness in both the Leine and Aller cyclothems illustrate a persistence of depressions and elevation in the same regions. The relief of the basement partly bore the character of local, closed depressions, where salts and anhydrites disclosed their highest thicknesses. The maximum thicknesses of the Werra, Stassfurt and Leine anhydrites are found in the region of Gubin - Sękowice. Because the greatest thicknesses of the Zechstein deposit of the individual cyclothems are grouped in the vicnity of Gubin, the name Gubin depression seems to be appropriate here. The development of the Zechstein deposits in the region of Gubin proves a marine origin of these sediments in the Werra, Stassfurt, Leine and in the lowermost part of the Aller cyclothems. The recession of the sea took place only in the upper part of this cyclothem, but the sedimentation, this time of continental nature, continued under condition of stable climate. The region of Gubin occurs within the chloride facies range, the southern boundary of which runs in the central part of the area. At the time of the Stassfurt cyclothem, the northern part of the region was within the area of the chloride facies with K-Mg salts, whereas the southern one was situated within the sulphate-carbonate facies. The course of the isobaths of the Zechstein bottom and top proves that the area here considered was remodelled due to the youngest - Tertiary orogenic movements, which were also responsible for the obliteration of the original relief.

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