Kilka uwag o zespołach otwornic towarzyszących wapieniom jasielskim w polskich Karpatach Zewnętrznych

Abstract

Opisano zespoły otwornic z otoczenia wapieni jasielskich regionalnego horyzontu korelacyjnego serii menilitowo-krośnienskiej polskich Karpat Zewnętrznych. Podano interpretację stratygraficzną i paleoekologiczną tych zespołów.

SOME REMARKS ON ACCOMPANYING FORAMINIFER ASSEMBLAGES IN JASŁO LIMESTONES IN THE POLISH OUTER CARPATHIANS

Jasło limestone are regarded as one of regional correlative lithological horizons in the menilite-Krosno series in the Outer Carpathians. They form two or, locally three separate horizons, the lower, first of which is best developed. In the Silesian and Dukla units, the lower horizon of Jasło limestones (Laminated Jasło limestones) occurs within sandstone-shaly Krosno beds. Individual limestone layers are separated by strongly calcareous shales with numerous pyrite micronodules. Pyritization also appears fairly advanced in the case of foraminifers and diatoms. The planktonic foraminifer assemblage found in direct neighbourhood of the lower horizon of Jasło limestones comprises the following species: Chiloguembelina gracillima (Andreae), Globigerina praebulloides Blow, G. officinalis Subbotina, G. angustiumbilicata Bolli, G. ciperoensis Bolli, G. occlusa Blow et Banner, Turborotalia nana (Bolli), T. brevispira (Subbotina). In some localities, there have been also found Turborotalia liverovskae (Bykova), T. cf. obesa (Bolli) and T. cf. siakensis (Le Roy) sensu W. Blow (1969). Accompanying benthic species, preserved as pyritic casts only, include: Loxostomum chalkophilum Hagn, Chilostomella tenuis Bornemann, Allomorphina trigona Reuss, Bolivina beyrichi Reuss, Fursenkoina schreibersiana (Czjzek), Bulimina cf. polymorphinoides Yokohama.

In the Skole and Subsilesian units, the lower horizon of Jasło limestones occurs among dark bituminous shales of menilite beds. Planktonic foraminifer assemblage found in these rocks is the same as in the Krosno beds whereas benthic foraminifer assemblage appears different. The latter includes: Bolivina crenulata Cushman, Neoeponides cf. haidingeri (d´Orbigny), Trifarina angulosa (Williamson), Caucasina schiskinskyae (Samoilova), Cibicides borislavensis Aisenstadt, Nonion granosum (d'Orbigny), Discorbis discoides (d'Orbigny), Rosalina limbata (Terquem) and Elphidium ex gr. laeve (d'Orbigny).

Foraminifers of the upper horizon of Jasło limestones (Zagórz limestones) were studied in localities in area of the Silesian unit, where horizon occurs in shaly part of the Krosno beds. Planktonic assemblage is essentially the same as in the neighbourhood of the lower horizon. It differs from the latter in the lack of Turborotalia liverovskae (Bykova), which may, however, be casual. Differences are similarly small in the case of benthic assemblages. The assemblage from the neighbourhood of the upper horizon comprises representatives of the genus Plectofrondicularia and the species Caucasina tenebricosa Pishvanova, more typical of higher part of the Krosno beds.

The occurrence of the species Turborotalia liverovskae (Bykova), T. cf. obesa (Bolli) and T. cf. siakensis (Le Roy) sensu W. Blow (1969) in assemblages from the lower horizon of Jasło limestones suggests origin of the strata in time interval corresponding to a zones of extremes in stratigraphic ranges of the taxa, i.e. the turn of the Rupelian and Chattian.

In preliminary foraminifer zonation of the menilite-Krosno series, the lower horizon of Jasło limestions is situated in upper part of range of the assemblage II. This corresponds to upper part of the zone P20 (W. Blow, 1969) or Globigerina ampliapertura Zone (H. Bolli, 1966) in the standard zonations. The datings based on calcareous nannoplankton appeared similar (zones NP 23/24).