The Late Cretaceous Fucoid Marl of the Ropianka Formation in the Kąkolówka Structure (Skole Nappe, Outer Carpathians, Poland) – lithology and foraminiferal biostratigraphy

Abstract

A 250-m-thick sedimentary succession dominated by siliciclastic deposits occurs in the Kąkolowka Structure of the Skole Nappe. The succession was deposited in the inner part of the Skole Basin during the Late Cretaceous. In position and age, it corresponds to the Kropivnik Fucoid Marl of the Wiar Member (a subdivision of the Ropianka Formation), which was comprehensively described in the external part of the Skole Nappe. In this study, the authors provide the first complete data set on the lithological development and biostratigraphy of the Kropivnik Fucoid Marl from the inner part of the Skole Nappe. The results are compared to previous data from the outer part of the Skole Nappe. In the Kropivnik Fucoid Marl of the Kąkolowka Structure, three main heterolithic facies associations are distinguished: shale-sandstone, marl-sandstone and sandstone-shale. The occurrences of hard, platy and soft marls within siliciclastic rocks are typical of the sections studied. The features observed indicate a turbiditic origin of the deposits studied, including the hard, platy marls. The allogenic material of the strata described includes the small, fragile tests of planktonic foraminifera, which were redeposited from the outer parts of the Skole Basin. Particularly large concentrations of planktonic foraminifera were observed in the hard, platy marls. They are less common in the soft marls and shales. In the Zimny Dzial section, a diverse assemblage of benthic and planktonic foraminifera was found. The Kropivnik Fucoid Marl was dated as uppermost Campanian to lowermost Maastrichtian on the basis of planktonic foraminifera, which represent the Gansserina gansseri Zone. The agglutinated foraminiferal assemblages are representative for the lower part of the Rzehakina inclusa Zone and the co-occurrence of the Caudammina gigantean (Geroch) acme with Rzehakina inclusa (Grzybowski) was observed.