Zlepieńce górnego syluru z otworu wiertniczego Raciborsko 2 na SW od Wieliczki

Wiesław Heflik, Konrad Konior


Upper Silurian conglomerates in the profile of the bore-hole Raciborsko 2 south-west of Wieliczka

The bore-hole Raciborsko 2 terminated in February 1971 was situated, 2.1 km north-east of the bore-hole Rzeszotary 2 and 2,4 km north-west from the bore-hole Raciborsko 1. The bore-hole pierced the Carpathian Flysch beds down to the depth of 293,5 m, then down to 658,0 m was drilled in Miocene beds, distinctly bipartite, and probably belonging to two tectonic units. Carbonate Upper Juraissic rocks were pierced in the depth interval 685,0—793,0 m, and Middle Jurassic rocks in the depth interval 793,0—798,0 m. Below, Permian rocks occurred in the depth interval 798,0—811,0 m. Below the depth of 811,0 m the bore hole penetrated conglomerates, and was terminated at the depth of 932,0 m, without reaching their base. Quartz porphyry was found in the uppermost part of the profile below the Permian beds, in a core 1 m long. The next cores, taken below the depth of 873,6 m consisted of conglomerate composed of pebbles and fragments of sedimentary, metamorphic and igneous rocks. The quartz porphyry from the depth 819,2—820,2 m is strongly weathered. Illite, quartz and hematite are the principal products of decomposition of the groundmass and the phenocrysts of the porphyry. The large content of illite and hematite suggest that the rock was weathered in an alcaline environment and warm and dry climate. The conglomerates penetrated in the depth interval 873,6—932,0 m are polymictic, and consist of pebbles of black siliceous shales, dark-grey fine-grained siliceous sandstones, quartz-mica shists (pebbles of these rocks have the greatest diameters), and red-brown siltstones, quartz porphyries, palaeotrachytes and palaeodadtes. All pebbles are weathered. The determination of the age of the conglomerates from the bore-hole Raciborsko 2 is very difficult. The conglomerates are lying under Permian siltstones, but they differ definitely from all known types of Permian conglomerates. As the conglomerates were not pierced toy the ibore-hole, the problem of their basement remains unsolved, but it is highly probable that the conglomerates are overlying metamorphic rocks which were stated in the nearby bore-hole Rzeszotary 2. Taking into account the post-Cambrian and pre-Silurian age of the metamorphism of lithologically differentiated Precamibrian sedimentary rocks (J. Borucki and M. Saidan, 1965), W. Heflik, K. Konior, 1971) and the presence of Silurian rocks in the bore-holes Piotrowice 1 (K. Konior, 1970) and Dąbie (S. Z. Różycki , 1953, S. Siedlecki , 1962), the authors are inclined to assign the described conglomerates to the Late Silurian. A younger age of the conglomerates seems not possible. The conglomerates from the bore-hole Raciborsko 2 are closely resembling the conglomerates known from Łapczyca (M. Turnau-Morawska, 1957), Batowice (J. Myszka, W. Parachoniak, 1958, S. Cebulak, 1958) and Mikluszowice, which were assigned to the Middle Ludlovian (K. Łydka , S. Siedlecki , H. Tomczyk, 1963). All these conglomerates are related with the Cracow phase of the Caledonian folding, although it can not be excluded that they represent the youngest, Ardenian phase, of this orogeny. The presence of the Upper Silurian conglomerates in the profile of the bore-hole Raciborsko 2 permits to delineate more accurately the south-western limits of the area of occurrence of Silurian in the subsurface.

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