Utwory dolnej kredy w południowej części Przedgórza Karpat

Stanisław Geroch, Antonina Jednorowska, Władysław Moryc


The Lower Cretaceous sediments in the Southern Part of the Carpathian Foreland

The pro file described below comes from the Stasiówka 1 bore-hole of the Dębica region (the southern, part of Poland). In this region the pre-Mioeene rocks consist, in descending order, of the Cretaoeous, Jurassic, Lower Triassie, Lower Carboniferous, Silurian and Precambrian sediments (Fig. 1, 3).
The stratigraphie profile of the Stasiówka 1 bore-hole (Fig 2.) is as follows :
0 — 15,0 m — Quaternary;
— 1.650,0 m — Inoceramian Beds (Upper Cretaceous), Skole unit of the Carpathian Flysch;
— 2.100,0 m — Miocene of the Carpathian Foredeep;
— 2,325,0 m — Upper Cretaceous (Turonian?-Campanian) developed in an epicontinental facies;
— 2.335,0 — Lower Cretaceous (probably Upper Valanginian);
— 2.509,0 m — Upper Jurassic (Kimmeridgian).
The stratigraphic boundaries were established on the basis of microfauna and lithology of rock fragments; electric logs were also used. The Low er Cretaceous sediments were found in a bore-core at the depth of 2,328,3 m — 2.334,5 m (cf. Fig. 2). The thickness of the Lower Cretaceous sediments in the Stasiówka 1 bore-hole does not exceed 10,0 m. These sediments 'comprise black and dark-grey, calcareous mudstones with tiny muscovite plates, pyrite and ra re quartz grains of a diameter up to 1 mm. Here and there intercalations of dark-grey, calcareous claystones can be seen, in these mudstones. In these sediments there are fragments of shells of Lam ellibranchiata, Gastropoda, Brachiopoda and Ammonoidea. The mudstones dips are 8— 10°. The microscopic examination of the mudstones and claystones showed rich fossil assemblage in the washed m aterial. They are Foraminifera, fragments of Echinodermata (Crinoidea, Echinoidea, Holothurioidea?), tiny shells of Gastropoda, Lamellibranchiata and fragment shells of Mollusca and Brachiopoda and probably fragments of Algae, Qstracoda, fragments of Bryozoa, and tin y shells of Brachiopoda are not so frequently found. Foraminifera occur mainly in the 0,1— 0,4 mm fraction. They are mainly benthonic calcareous Foraminifera. If we consider the number of species, Nodosariidae prevail, w hile in respect of the number of specimens Epistomina predominate (up to about 25%) as well as Trocholina and Spirillin a (together up to about 20%). In the fraction, thicker than 0,4 mm Foram inifera are rarely found and they are usually arenaceous forms of the Haplophragmium genus. Among Foraminifera and Ostracoda the determined species are listed in th,e Polish text p. 413. The overlapping stratigraphic ranges of the index species (Fig. 4, Pl. LII, LIII) show that the age of the examined sediments corresponds most probably to the Upper Valamginian. The majority of the determined species are (known to occur in the Lower Cretaceous of the Central Poland (Sztejn, 1957, 1967, 1968, 1969a, 1969b). In addition there are ¡species not ye t reported from Central Poland such as Spirillina cf. italica, Patellina turriculata (Dieniet Massari 1966 — Sardinia ; Gorbatchik 1971 — Crimea), Melathrokerion spirialis (Gorbatchik 1968, 1971 — Crimea), Trocholina burlini (Gorbatchik 1959, 1971 — Crimea, Caucasus; Geroch 1966 — Carpathians; Guillaume 1963 — Jura ). Lithologically, the Lower Cretaceous sediments from the Stasiówka 1 bore-hole show similarity to the Lower Cretaceous sediments from Central Poland. Thus, the sediments from Stasiówka represent a small remnant of once more extensive epicontinental marine deposits w hich were subjected to erosion already during the Cretaceous and late r during the Paleogene. The sediments under consideration have been deposited in a marine basin which was connected w ith that of the Central Poland. The discovery of these sediments at Stasiówka points to a much more extensive southward distribution of the Lower Cretaceous epicontinental deposits than hitherto assumed. The relationship of these deposits and the Lower Cretaceous flysch sediments in the Carpathians remain an open, question.

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