Łupki z egzotykami z warstw krośnieńskich w rejonie Baligrodu

Andrzej Ślączka, Tadeusz Wiesser



The presence of exotics in the Krosno beds south of Baligród has been deter-mined during the recent war years by O. G a n s s. Further investigations were made in 1954-56 by one of the present authors (A. Ś l ą c z k a, 1959a). These exotics appear in the Bóbrka-Rogów fold (Fig. 1) in a bank of some 50 m. thickness (Fig. 2). Besides crystalline exotics, Eocene zoogenic limestones, blocks of conglomerates, fragments of melinite green marls and shales appear here also. The exotics are scattered at random, in .a bank of unstratified siltstones. Observations revealed that the discussed shales were laid down, together with the exotics, by a submarine slide derived from the northwestern extension of the Rachów massif. This same massif presumably supplied the coarsegrained Krosno sandstones of this part of the Carpathians. The distance of transportation has been some 50 km. The provenance of the material from this region is also indicated by the composition of the crystalline exotics. By means of microscopic examinations, the exotics of this type can be classified as: phyllites, albite and albite-calcite gneiss-phyllites, garnet phyllites and phyllitic epidote-albite amphibolites. The exotics represent products of a regional and a particularly dynamic metamorphism mostly of sedimentary pelitic rocks or, more rarely, of extrusive rocks. In principia, this metamorphism has been progressive and its deformations were mostly synkinematic. In this period a marked albitization of the phyllites and of similar rocks took place. The subsequent action of hydrotherms, revealed in carbonitization and vermiculitization (of biotite), interfered with weathering features in the exotics, and therefore the range of this action is difficult to define. Numerous examples of macro- and microfoldings of the phyllite rocks, the presence of systems of fissures cutting each other long an axis parallel with the axis of the microfolds, as well as the orientation of linear structures in the amphibolites, - all these features prove these rocks to be - from a petrotectonic point of view - so-called B-tectonites. The processes of alteration of the biomes (vermiculitization) preclude a definition of the absolute age of the exotics by means of the only method feasible, the potassium-argon method. Parallelization, carried out by the authors, clearly indicates a high degree of correlation of the investigated exotic rocks with the crystalline rocks building the Rachów massif, which latter has been investigated in detail by Ł. T k a c z u k and D. G u r ż i j (1957). Most probable seems a close connection of this massif with the cordillera which in the Palaeogene was intensely degraded and thus became a source of the Bieszczady exotics.

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