Provenance analyses of the Late Cretaceous - Palaeocene deposits of the Magura Basin (Polish Western Carpathians) - evidence from a study of the heavy minerals

Abstract

The Late Cretaceous-Palaeocene sequence of the Magura Nappe in Poland is underlain by the Albian-Cenomanian spotty marls at the base and overlapped by the PalaeoccnelEarly Eocene variegated shales at the top. The spotty marls arc followed by variegated shales and then by turbiditic deposits. The upper boundary of the variegated shales is diachronous - older in the Rata zone (Santonian) and younger in the Klynica zone (Campanian/Maastrichtian). The turbiditic deposits of the marginal (northern) zone of the Magura Nappe display palaeocurrent directions from the NW in the western part and from the NE in the eastern part. In other parts of this unit palaeocurrent directions from the SE and E were observed. The northern source area of the Magura Basin is commonly connected with the Silesian Ridge, while the south-eastern one could be connected with an accreted fragment of the Inner Carpathians. The heavy mineral assemblages of the Magura Nappe are dominated by stable and ultrastable species. Chromian spinels occur additionally in the Krynica zonc and to some extent in the Bystrica and Raca zones. Investigation of the chemical composition of the heavy minerals showed that that the southern source area was built of low- to medium-grade metamorphic rocks, as well as igneous rocks associated with ophiolite sequences. The chemical composition of minerals deriving from the NW indicates that they Clystallized mainly in low- to high-grade metamorphic rocks and granitoids.