Stratygrafia syluru w północno-wschodniej Polsce

Abstract

SILURIAN STRATIGRAPHY IN NORTHEASTERN POLANDIn 1957-1961 the Silurian deposits of the East-European platform area have been encountered in the following bore holes: Łeba 2, Łeba 3, Bytów, Pasłęk, Bartoszyce, Gołdap, Żebrak, Mielinik, Tłuszcz, Krzyże and Kaplonosy. The whole of the material obtained from these bore holes is as much as 8000 m of drill core. The fauna prepared of the drill core is very rich and numerous, thus more detailed study moo the carried on in the future.The Silurian basin in Poland extended over a fairly vast area and constituted the eastern branch of the North-European geosyncline. In the southeast, the basin was restricted by the Święty Krzyż anticlinorium, in the northeast by the East-European platform. In general, it represented a continuation of the Ordovician sedimentary cycle. However, as compared with the Ordovician basin, the sedimentary basin of the Silurian in Poland is characteristic of deepening and widening of its extent. The epicontinental character of the sea existing at the Ordovician time considerably changed during the Silurian into a miogeosynclinal one, especially in the central part.As concerns lithological development and zonal distribution of shallower and·deeper neritics, the Silurian of the platform is closely connected with the Russian platform area, particularly with the Silurian of the Baltic countries, and with the Scania area, partly also with the Silurian of Gotland. Moreover, the shallower neritics show great analogies with the Silurian occurring in the Wolynia and Podolia areas.A similarity to the area of the Święty Krzyż Mts. is also distinctly visible, particularly as concerns the Platform Silurian deposits which have been reached within the deeper zones of the so-called marginal synclinorium in such profiles as Lębork, Bytów, Pasłęk and Żebrak. In these profiles an argillaceous facies with graptolites predominates. Sporadically, there occur also calcareous lenses and concretions which are found in the Bardo and the Prągowiec beds of the Święty Krzyż Mts.The so far applied subdivision of the platform Silurian in Poland shows that almost all the equivalents of the graptolite zones are here richly represented by species of index graptolites (see stratigraphical table) proving an open basin character and a convenient connection with the neighbouring areas.The stratigraphical subdivision of the Silurian is mainly based on the assemblages of graptolites represented here in quantities. For individual complexes or stratigraphical series the author introduced new nomenclature of beds. Hence, the lowermost Pasłęk beds are an equivalent of both Llandoverian and Wenlockian stages, however, the Mielnik beds comprising also the zone Saetograptus leintwardinensis and the overlying Siedlce beds together with the extension area of the  graptolites ex gr. formosus, correspond to the Lludlovian stage. A detailed description of these·beds and a list of faunal assemblages occurring in the area discussed, are given in the Polish text.The upper argillaceous deposits with graptolites appearing above the Siedlce beds probably are not an equivalent of the British Lludlovian stage. Therefore, the so far determined deposits as Podlasie beds are called now by the present author - Podlasie stage. As concerns the platform Silurian in the argillaceous fades with graptolites, this stage should characterize the younger deposits than the equivalents of the British Lludlovian stage, however, with tills reservation that there does not exist a detailed correlation of the top part of the Siedlce·beds o)r of the bottom part of the Podlasie stage with the uppermost Lludlovian (Upper Whitcliffe·beds) of Great Britain. In the bore hole Kock a trylobite Acastella heberti elsana has been found to occur in the argillaceous fades without graptolites. This form is characteristic of the lower part of the Bostów beds in the northern area of the Święty Krzyż Mts. It is also possible that the deposits of Kock, determined as Kock beds, may already represent the equivalents of the lowermost Gedinnian and are younger than those of the Podlasie stage (E. Tomczykowa, 1962).