Czerwony spągowiec platform prekambryjskiej – miąższość i facje

Jędrzej Pokorski




In the general, the boundary of two provinces, characterized by a different development of the Rotliegendes, coincides with the margin of the Precambrian platform. Within this platform the Upper Rotliegendes (Saxonian) is built up mainly of conglomerates and of arkose of greywacke sandstones subordinately also of siltstones and caystones.
The Saxonian deposits are characterized by the cyclic structurre. In the large Saxonian cyles, called further a macrocyle, the rocks from the Palaeozoic platform probably belong to one macrocycle or its part, i.e. the youngest macrocyle that ends the sedimentation in the Saxonian. The deposits of this macrocycle consist of several, commonly very small and simple cycles. To the conventional components of the simple cycles belong here conglomerates (A), sandstones (B) and siltstones (C). On the basis of 64 bore holes both thickness (Fig. 1) and lithofacial map (Fig. 2) have been worked out. The lithofacial map has been constructed by the superposition of two maps: the map of croarse-clasticity index P + Z/M and the map of the sandstone-conglomerate coefficient – (Table 1). These maps, together with the schemes of the simple cycles (Table. 1) characterize the regional and the local changes in facies.
In the area of the Peribaltik depression four alluvial cones (Figs. 1 and 2), and in the Podlasie depression – three alluvial cones can be distinguished, the latter occurring at the northern margin of the basin (Fig. 1). In the southern part of the depression alluvial cones have not probably been developed. The spatial arrangement of the distinguished lithofacial types (Fig. 2), and the thickness distribution (Fig. 1) point to the differentiated size of the alluvial cones. The general size of the cones decreases westwards. The alluvial cones of the Podlasie depression are characterized by smaller thicknesses, and are not so extensive as those of the Peribaltic depression.
Within the alluvial cones and the river beds there are found, as a rule, five main cycles, predominantly of AB type. The area of the overflooding terrace distinguishes itself a reduced amount of slimlple cycles, in the extreme even one cycle of BC type, or by one inversed cycle of CB type. Petrlological and sedimentological features allow the formations under consideration to be referred to the alluvia of a glen river.
The main sedimentation area was in the Mazury-Suwałki elevation. The Saxonian formations were laid down within the troughs formed in its northern and southern margins. The Rotliegendes deposits occur in these platform areas, where the crystalline basement is built of the Giothis complexes. The accretion zone of the Gothish complexles to the Svekofenno-Karelian System and its central massifs had been tectonically active also in the Palaeozoic, anyhow at the close of the Saxionian, and lasted with the decreasing intensity throughout the whole Zechstein period.


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