- Tytuł:
-
Environmental changes around the Cenomanian-Turonian boundary in a marginal part of the Outer Carpathian Basin expressed by microfacies, microfossils and chemical records in the Skole Nappe (Poland)
Zmiany w głębokowodnym środowisku brzeżnej części basenu Karpat Zewnętrznych wokół granicy Cenomanu i Turonu wyrażone w zapisie mikrofacji, zespołach mikroskamieniałości i chemizmie utworów w Płaszczowinie Skolskiej - Autorzy:
- Bąk, K.
- Powiązania:
- https://bibliotekanauki.pl/articles/191678.pdf
- Data publikacji:
- 2007
- Wydawca:
- Polskie Towarzystwo Geologiczne
- Tematy:
-
Cenomanian-Turonian boundary event
microfacies
benthic foraminifers
bulk geochemistry
Outer Carpathians
Polska - Opis:
- Lithology, microfacies, benthic foraminiferal and bulk chemical analyses of the Spława section in the Skole Nappe, Outer Carpathians (Poland) reflect environmental changes across the Cenomanian-Turonian transi- tion. Biogenic-rich-turbidite sedimentation preceded the organic-rich sedimentation in the Skole Basin, termina- ting in the latest Cenomanian in response to progressive eustatic sea-level rise and to expansion of an oxygen minimum zone. The uppermost Cenomanian black, laminated, organic-rich shale series records the oceanic anoxic event (OAE-2). The benthos-free black non-calcareous shales exhibiting positive excursions of chemical redox indexes are indicative of bottom-water anoxia, interrupted by periods of suboxic conditions with sedimentation of hemipelagic green shales with poor agglutinated foraminiferal assemblages. An extremely low sedimentation rate or even a hiatus and an increase in deep-water circulation causing basin oxygenation resulted in precipitation of a ferromanganese layers and siliceous-manganiferrous variegated shales, as documented by low values of chemical redox indices. However, the lack of benthos and bioturbation, and low values of the Ce/La ratio in the subsequent succession of variegated shales (dominated by green shales) indicate a return to stressed conditions at basin floor with sluggish bottom water circulation, which occasionally resulted in sea floor anoxia with deposition of organic-rich shales. The long-termed well-oxygenated conditions at the basin floor appeared in the Early Turo- nian, as documented by diversified benthic foraminiferal assemblages. The frequency of radiolarian-rich layers and Ba/Al and Ba/Sc ratios increase up-section, reflecting an increase in primary productivity, induced by upwelling circulation.
- Źródło:
-
Annales Societatis Geologorum Poloniae; 2007, 77, No 1; 39-67
0208-9068 - Pojawia się w:
- Annales Societatis Geologorum Poloniae
- Dostawca treści:
- Biblioteka Nauki
Artykuł