Rocks of effusive origin have been identified in the younger polymictic conglomerate horizon of the Zdánice-Hustopece Formation (Tertiary) of the Zdánice-Subslesian unit. The conglomerates consist of sedimentary, plutonic and metamorphic rocks; the presence of volcanics in this varied assemblage has so far been unknown. Although they are rather scarce and poorly preserved, rocks of aphanitic-porphyrite type, rhyodacites and pyroxene-albite andesite have been petrographically determined. Radiometric dating of andesite gave an age of 296 m. y., which corresponds to the Upper Carboniferous. The source area of effusives was most probably the cordiolera which divided the flysch sedimentary basin into the outer Zdánice-Subsilesian sector and the inner Magura sector.