Biostratygrafia i wiek izotopowy pogranicza środkowego i górnego eocenu w otworze wiertniczym Szczecin IG1

Ewa Odrzywolska-Bieńkowa, Krystyna Pożaryska

Abstract


W otworze wiertniczym Szczecin IG 1 na głębokości 190–281 m stwierdzono obecność osadów najwyższej części eocenu środkowego na podstawie badań zespołów otwornicowych (E. Odrzywolska-Bieńkowa, K. Pożaryska), nannoplanktonu wapiennego (E. Martini, RFN) oraz wieku izotopowego (H. Kreutzer, RFN). Przeprowadzono korelację badanych utworów z równowiekowymi osadami NRD, ZSRR, Belgii, Francji i Anglii. Porównanie z osadami piętra bodrackiego w ZSRR utrudniają różnice w rozwoju facjalnym, natomiast z osadami rejonu Hampshire w Anglii brak numulitów w zespole fauny NW Polski.

 

BIOSTRATIGRAPHY AND ISOTOPIC AGE OF MIDDLE AND UPPER EOCENE JUNCTION BEDS FROM THE SZCZECIN IG 1 BOREHOLE

The studies on foraminifers (E. Odrzywolska-Bieńkowa and K. Pożaryska) and calcareous nannoplankton (E. Martini, FRG) and radiometric datings (H. Kreutzer, FRG) showed that deposits occurring at the depth of 190–281 m in the Szczecin IG 1 borehole (NW Poland) are of the Middle Eocene age. The studies were carried out within the framework of the IGCP Project 124, the NW –European Tertiary Basin. E. Martini differentiated here two nannoplankton zones, NP 15 (Chiphragmolithus alatus) and NP 16 (Discoaster tani nodifer), identical as those from the upper parts of Middle Eocene of GDR, FRG, Belgium, England and USSR. Taking these datings into account the present authors reanalyzed stratigraphic ranges of foraminifers recorded here. Table 1 shows foraminifer species recorded in upper parts of the Middle Eocene in the Szczecin IG 1 borehole profile and coeval deposits of GDR, FRG, USSR, Belgium and France.

It follows that the Polish assemblage is most close to those from GDR, Belgium and France. The differences in respect to the foraminifer assemblage from the Bodrak stage in the USSR (uppermost Middle Eocene) may be explained by differences in facies. Benthic species predominate in deposits penetrated by the Szczecin IG 1 borehole and planktonic ones – in marly deposits of the Bodrak stage. The correlation of the Szczecin profile with that from England (Hampshire Basin) on the basis of foraminifers is difficult as the latter! are dated by nummulitids which are lacking in the Szczecin IG 1 borehole. Radiolarians occurring in masses in basal part of the profile make possible a reliable correlation with coeval deposits from GDR and USSR.


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