Szary spągowiec w okolicy Nowej Soli

Maciej Podemski




Lower Permian clastic formations are the immediate basement of the clay-marly Zechstein deposits in the vicinity of Nowa Sól. In the top part, these are built up of fine-grained quartz sandstones, disclosing at places intercalations and interbeddings of conglomerate-like sandstones and of conglomerates. It has been ascertained that coarse-clastic material as a rule occurs in the areas, which constituted various elevations of the bottom of the evaporation basin during the Zechstein sedimentation. Beside quartz the clastic material reveals also feldspars (microcline, plagioclases), micas, heavy minerals (zircon, tourmaline) and fragments of metamorphic rocks (quartzites, phyllites). Cementing material consist mainly of silica (quartz, chalcedony) and carbonates. In minor amounts are found clay minerals and brown-red iron compounds. Chaotic structures prevail, although parallel bedding, usually very regular, at places of fractional nature, may also be observed.

The rock is, as a rule, red in colour; however, at the top the colour passes into pink or light grey. These changes in colour  are highly irregular, red and grey portions are interfingered, and at the top maybe observed either completely red, or grey colour. Thus, any uniform, decolourized zone cannot be distinguished in these deposits in the vicinity of Nowa Sól. The above changes in colour are due to the removal of trivalent iron compounds from matrix. It has been ascertained that this process developed gradually, without any disturbance in rock structure. Thus, a conclusion has been drawn that the decolourized parts, called (according to U. Kriebel, l967) Grauliegendes, belong here, from the stratigraphical point of view, to Rotliegendes.
Both the observations made in the vicinity of Nowa Sól and those from the other areas of the Fore-Sudetic monocline point to a fact that the decolourization of the Rotliegendes formations took place most intensely and reached the deepest horizons, where sulphide mineralization appeared in the decolourized deposits. In consequence of the results obtained a proposition has been submitted that mineralizing solutions (apart from their origin) were the most important decolourizing agents here.



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