The Eastern Sudetic Island in the Early-to-Middle Turonian: evidence from heavy minerals in the Jerzmanice sandstones, SW Poland

Abstract

The Eastern Sudetic Island was an emerged area in the late cretaceous shelf-sea of central Europe that delivered coarse siliciclastic material to adjacent basins. The extent of this land area during the Early-to-Middle Turonian has been reconstructed on the basis of a heavy-mineral analysis of the Jerzmanice sandstones from the North Sudetic Basin. The heavy minerals studied predominantly derive from medium to high grade metamorphic rocks, such as granulites and metabasites, calc-silicate rocks, mica schists and gneisses, and from garnet peridotites and pegmatites/granites. The interpretation of various heavy mineral species provides evidence that the major part of the detritus constituting the Jerzmanice sandstones was supplied from a relatively small area of the fore-Sudetic part of the Góry Sowie Massif and its immediate vicinity, approx. 50 km away from the depositional site. Heavy minerals and particularly the chemical characteristics of detrital garnets, cr-spinels and tourmalines, have turned out to be excellent indicators of the provenance of these mature late cretaceous sandstones.