Palynology of the deep structures of the Carpathian Foredeep (3,950– 5,467 m) at the front of Carpathian overthrust, the NS-1 Borehole, SE Poland

Przemysław Gedl, Piotr Śmist, Elżbieta Worobiec


The current paper presents the results of palynological studies from deep structures at the front of the Carpathian overthrust, penetrated by the NS-1 Borehole. Both the method used and hardly accessible material from a depth of almost 5.5 km allow the presentation of new data from the Stebnik Unit, the underlying autochthonous Miocene succession, and the conglomerates that rest upon the crystalline basement. Samples collected from available cored intervals and cuttings from the lower part of the borehole provided the opportunity to study for the first time the palynological content of the strata under consideration. Samples yielded diversified material, composed of terrestrial and marine elements, commonly showing various stages of preservation. The latter indicate various origins for the material analysed, which is possibly at least partly recycled. The occurrence of this phenomenon, particularly in the Stebnik Unit and the upper part of the autochthonous Miocene sequence, confirmed also by results of earlier micropalaeontological studies, makes precise stratigraphic correlation highly debatable. The authors discuss the possibility of both Paleogene and Miocene ages for the material. Also highly debatable are the palaeoenvironmental reconstructions of this interval, although the general intense influx of terrestrial material recorded is probably responsible for the unfavourable conditions for planktonic biota. Different, optimal marine conditions can be deduced for the lower part of the autochthonous Miocene; an abundance of dinoflagellate cysts allows their precise correlation with coeval strata of the Carpathian Foredeep Basin. Palynological analysis of conglomerate matrix material gave negative results. However, this and the lithological characteristics indicate a different origin and age of these strata in comparison with other coarse-grained lithosomes, known from neighbouring areas. The generally immature state of preservation of the organic matter in the deepest part of the borehole indicates that this part of the succession was not affected by the high temperatures that would be expected at such a depth. This contrast with the much more mature palynomorphs of the overlying Stebnik Unit points to the fact that these strata were heated to a much higher degree prior to their final burial.

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