„Przerwa hydrochemiczna” w podłożu miocenu zachodniej części zapadliska przedkarpackiego

Abstract

"HYDROCHEMICAL GAP" IN THE MIOCENE SUBSTRATUM OF THE WESTERN PART OF THE CARPATHIAN FOREDEEPSummaryA several hundred metres thick series or Miocene deposits, occurs in the south-western part of the Carpathian foredeep. At the bottom of this series are found clastic deposits from about ten to over 200 m in thickness, restricted, however, to the depressional areas of the substratum only. In the substratum are found culminations characterized by a W-E trending direction of axes, separated by depreesions. On these culminations 3 bore holes have been completed showing an increased water mineralization in the Miocene deposits (56.7 g/l). In the substratum, in turn, water mineralization amounts to 13.5 g/l – 32.5 g/l only. Similar phenomena have been observed by V. Homola (1959) to appear in the regions of Przybor – Starzyce and Żuków, where the mineralization of waters in Carboniferous formations amounts to 10.5 g/l, and that of the overlying Miocene beds as much as 50 g/l. East of the area here considered, i.e. in the region of Bielsko and Kęty, the mineralization of the Upper Carboniferous waters was from 22.5 to 31.3 g/l, and that of the overlying Miocene deposits reached even up to 66.5g/l. The, decreased mineralization of waters in the substratum cannot be related to the present-day freshening process. This is proved by the overlying Miocene series, several hundred metres in thickness, and by the presence of mineralized sedimentary marine waters in them (A. Różkowski, 1962). Such a decreased mineralization was referred to the freshening of the mineralized waters that had already existed in the substratum, before the sedimentation ·of the marine deposits (J. Pałys, 1966). The most considerable decrease in mineralization may be observed in the areas, which, before the Miocene marine transgression were highly uplifted, i.e. in the south-western areas, as well as in the areas of buried culminations of the substratum. The dip of the then continent towards NE has been geologically documented, by the character of distribution of the Lower Opolian (Lower Tortonian) facies that changes from continental to marine (S. Alexandrowicz, l963). Process of freshening of mineralized waters that took place in the substratum during the continental period before the marine transgression, was of regional extent. At present, this may be observed as a “hydrochemical gap”, the appearance of which in the vast areas of the Carpathian foredeep has been proved in this paper.