Tektonika paleozoiku podpermskiego obszaru warszawskiego

Władysław Pożaryski, Henryk Tomczyk, Wojciech Brochwicz-Lewiński



Maps of depth of occurrence of top surface of crystalline basement and distribution of thickness of pre-Permian Paleozoic and Carboniferous rocks and geological map of Permian subcrops were compiled on the basis of analyses of over 30 deep borehole columns and 22 refraction seismics sections. In the Paleozoic times, the studied area belonged to the Warsaw Block of the epi-Gothian Platform (W. Pożaryski, 1973) and its southern part, corresponding to southern slope of the Block, was representing at the same time an element of latitudinal Podlasie Depression.
The comparison of the map of distribution of thickness of (pre-Permian Paleozoic rocks and geological map of Permian subcrops showed that the present-day distribution of thickness of these rocks is mainly the result of erosion in the pre-Saxonian and post-Westphalian as well as Early Carboniferous and Devonian times. Moreover, it revealed several lower-order pre-Permian structures: Dębe tectonic trough, Raciąż trough (possibly synsedimentary in character) and Rypin Depression, separated by Bodzanów and Sierpc elevations, respectively, and Brodnica Block, Toruń Depression and Szczawno-Bieżuń tectonic trough. There were also found several important SW-NE oriented fault zones which delineate units such as Dębe and Raciąż troughs. The studies showed that the Carboniferous Masovian-Lublin trough is turning WNW in the vicinities of Maciejowice and Magnuszew. Between Grójec and Warka, thickness of Carboniferous rocks increases to over 1500 m in axial part of the trough.
The record of Carboniferous rocks on slope of the Racibórz trough (Sierpc 2 borehole) suggests that the trough may be infilled with a thick series of the Upper Carboniferous. The wealth of coal detritus (up to 2.5 cm in size) in rocks assigned to the Westphalian D (A. M. Żelichowski in: Project of the Bodzanów IG 1 borehole, 1979) indicates erosion of older, coal-bearing series in direct proximity of the trough and, at the same time, the possibility of their preservation in the trough. When the presence of coal deposits is confirmed by further studies, they will appear potentially useful by means of underground gasification sometime in the future, on account of their geological setting (occurrence in trough at depths over 4000-5000 m, under a thick, sealing cover of Zechstein salt). Such geological setting also makes the studied Carboniferous perspective for search for gas.

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