Depositional environment and provenance of the GrestenFormation (Dogger) on the southeastern slopes of the BohemianMassif (Czech Republic, subsurface data)

Abstract

The deposits of the Gresten Formation (Midle Jurassic) obtained from deep wells in the territory of southern Moravia (Czech Republic) have been newly examined with the aim to better describe their provenance and depositional environment. Deposition within a relatively broad flood plain with fluvial/distributive channels, crevasse channels, crevasses splays and coal-swaps have been recognised in the majority of well cores. Basinal/open marine deposits have been less common. The heavy mineral association is quite stable, with significant dominance of garnet and commonly also with high content of zircon. The mineralogical spectra of garnet types were broad with strong dominance of almandines. The rutiles were mostly derived from metapelites and additionally also from metamafic rocks and pegmatites. The results point to mixed sources from both intensively weathered crystalline rocks of the eastern margin of the Bohemian Massif (primary source) and the older sedimentary rocks - especially from the Moravo-Silesian Paleozoic deposits (recycled source).