Poziomy wapieni kokkolitowych w serii menilitowo-krośnieńskiej - rozróżnianie, korelacja i geneza

Grzegorz Haczewski


Coccolith limestone horizons in the Menilite-Krosno series (Oligocene, Carpathians): identification, correlation and origin

Bands of pelagic coccolith limestones occur in Oligocene strata of the Menilite- Krosno series, at several separate horizons. The limestone horizons are isochronous markers. Difficulties arise in their use, because of confused nomenclature and lack of precise criteria for their identification. Tylawa limestones, finely laminated, with abundant fossil fishes and no planktonie foraminifers occur above the basal cherts of the Menilite Beds and above, or at the top of the so-called Dynów marls. They form a few separate horizons. The Jasło limestone passes laterally from the Menilite Beds in the Skole unit, to the Upper Krosno Beds in the inner part of the Silesian unit. It consists of 26 cm of laminated limestone with abundant fossil fishes and planktonie foraminifers, underlain by 5 cm of non-laminated limestone. The Zagórz limestone, crudely laminated, is up to 20 cm thick and occurs 6-150 m above the Jasło limestone. The Folusz limestone is weakly lithified nannochalk with infaunal trace and marked clastic admixture. The laminae in the Jasło limestone are correlated for up to 240 km and across major structural-facies units. In the Zagórz limestones, the laminae have been correlated for 550 km. In the Tylawa limestone the laminae have been correlated for 750 m. The correlation of laminae permitted palaeobathymetrical analysis, studies of lateral changes in turbidites, and investigation of seismically induced sedimentary phenomena. The limestones were laid down in a restricted basin when temporary nutrient traps were provided by structure of the water column. Low concentrations of nutrients fostered intense and extended blooms of coccolithophores. These were grazed by zooplankton and sank to the bottom in its faecal pellets. The Jasło limestone was laid down during thermal stratification, the Tylawa limestone during haline stratification. The Zagórz limestone originated in conditions of a steep density gradient. The Folusz limestone possibly is a shallower equivalent of the Jasło limestone. The limestone horizons are traced along the whole Carpathians, and they are possibly recognizable in the whole Paratethys.

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