Charakterystyka geologiczna podłoża permu obszaru przedsudeckiego

Abstract

Omówiono budowę geologiczną utworów podpermskich obszaru przedsudeckiego na podstawie wyników prac geofizycznych, korelacji danych z wierceń przy uwzględnieniu badań petrograficznych, palinologicznych i paleontologicznych. Podano charakterystykę profilu utworów podpermskich i zarys tektoniki. przedstawiono przebieg granic geologicznych, wydzielono większe elementy strukturalne i schemat głównych Iinii tektonicznych.GEOLOGICAL FEATURES OF THE PERMIAN BASEMENT IN THE FORE-SUDETIC AREA The recent drilling data have been used to modernize the geological map with no the younger than Carboniferous formations of the Fore-Sudetic area. The map was presented in the author's previous work (K. Wierzchowska-Kicułowa, 1984). As a result of reinterpretation of refractional survey from 1964 -1978 data have been obtained on the geological features. Additional information for petrographic investigation, better correlation of profiles, and possibilities of correction of formerly accepted geological borders was obtained. The Precambrian formations are found in some boreholes in the Oleśnica area. Beneath the Permian a series of formations from Eocambrian to Older Palaeozoic was found in the area between Wolsztyn and Leszno. The Devonian (Frasnian-Famenian) formations were found in two boreholes in the southern part of the area and in the Zbąszyn 2 borehole (the Wolsztyn - Leszno block). Their age has been determined in the duration between Givetian and Upper Fransian. Formations of the Lower Carboniferous from Tournai to lower Upper Visean have no palaeoontological dating. In the Rawicz - Ostrów Wlkp. - Ostrzeszów area the highest Upper Visean sediments have been documented by gonialites. Above then the Namurian A formation occurs concordantly dated by either goniatites or sporomorph complexes in same profiles. Similitude with the beneath -occurring Lower Carboniferous sediments makes their division difficult (Fig. 1). In some profiles the Namurian B - C and Westphalian formations have been distinguished. The Stephanian formation is known from one borehole in the Zielona Góra area. In a result of the latest geophysical survey a course of faults in the Myślibórz-Gorzow Wlkp. region has been reconed. A course of the Leszno fault has been reconed closely. The Oleśnica - Poznań fault has been confirmed.A question of the SW - NE faults in the Ostrów Wlkp., Ostrzeszów, Wieluń region has been analysed. Closely determined the Dolsk fault divides the southern faulting zone connected with the Erzgebirge phase from the northern zone where the Asturian phase movements tock place. The main structural elements originated in the process of the overlapped folding and disjunctive movements. Depressed and elevated zones showed in geological sections (Figs. 2, 3) outlined visibly. In many areas folding movements were of overthrust type. Such a structure pattern is shown between the Wolsztyn and Kościan blocks, in the Ostrów Wlkp. and Ostrzeszów regions, as well as in the Asturian phase movement zone e.g. in the Rokitnica. Poznań, Środa and Kalisz areas. This problem is here slightly documented.