Provenance study of Permian non-marine sandstones and conglomerates of the Krkonoše Piedmont Basin (Czech Republic): exotic marine limestone pebbles, heavy minerals and garnet composition

This study focuses on identifying major source areas in several stratigraphic intervals in the Permian sediments of the Krkonoše Piedmont Basin and integrates it with existing sedimentological data. Pebbles in Cisuralian-Guadalupian conglomerates of alluvial fans, nearshore lacustrine and lacustrine fan-delta deposits that were deposited close to the northwestern and southeastern basin margin, respectively, correspond almost exclusively to local material from adjacent crystalline complexes. The heavy mineral associations of the sandstone matrix of these conglomerates support this interpretation. Crystalline units of the south-western part of the Krkonoše-Jizera Crystalline Complex and Orlice-Sněžník Crystalline Complex, respectively, are considered as the most favourable sources. Heavy mineral associations of fluvial sandstone facies are of complex composition pointing to repeated recycling of clastic material. However, heavy mineral indices reveal distinct source areas for the main lithostratigraphic units. Two main possible source areas for the fluvial Asselian deposits (Vrchlabí Formation) of the south-western part of the basin were found. Pebbles of late Devonian- early Carboniferous marine limestones probably came from the central part of the hypothetical Jítrava-Hradec Basin. The garnet compositions in sand detrital material point to leucogranites and pegmatites of the north-eastern Moldanubian Zone, Přibyslavice area, as the possible source rocks. Guadalupian fluvial deposits reveal a wide range of sources that can be attributed to the recycling of detrital material from Cisuralian and Carboniferous deposits. Garnet compositions indicate Moldanubian granulites, garnet clinopyroxenites, leucogranites and pegmatites as a possible sources. We infer that Moldanubian granulites and garnet clinopyroxenites were exposed to an erosion level in the Early Permian at the latest