Acta Musei Moraviae

Interpretation of depositional environment and provenance of sedimentary rocks in the Výkleky Quarry (Moravice Formation, Nízký Jeseník Culm Basin)

The five cores were drilled out in the Výkleky Quarry, in which sedimentary rocks of the Moravice Formation of the Nízký Jeseník Culm Basin are quarried. Detailed lithological description and photodocumentation were performed and each drill-core was sampled for optical microscopic analysis. The studied sedimentary sequence includes various gravity flow deposits, including debris flow, grain flow or turbidity flow sediments. Hemipelagic sediments, representing basin floor environment and pebbly mudstone, representing deposition from the submarine slide, also occur. The vertical sequence reveals progradation of the submarine sand-rich fan onto the basin floor. The dominant part of the sedimentary sequence is represented by distributary channel and sandy lobe deposits of the middle part of the submarine fan system. The provenance analysis based on the Gazzi-Dickinson point-counting method allows interpreting the geotectonic position of the source area in the recycled orogen with the transition to the magmatic arc. Various types of metamorphic rocks predominate over sedimentary and plutonic rocks in the clast assemblage of petromictic conglomerates. This association is similar to the composition of the Račice conglomerates of the Drahany Culm Basin and corresponds to the expected dominant supply of clastic material to the Culm basin from a point source situated in the southern part of Drahany Upland. In contrast, the clast assemblage of pebbly mudstone indicates provenance from local source. The dominance of clasts of acid volcanic rocks corresponds to the intense terrestrial volcanic activity during deposition of the Cvilín and Brumovice Beds of the Moravice Formation. It also demonstrates the complex morphology and presence of temporary depocentres at the front of the Variscan accretion wedge, as can be observed in modern peripheral foreland basins.