Two diatreme structures in the Lusatian Mountains (CZ) can be assigned to so-called pre-rift period of volcanism within the Bohemian Massif. This is confirmed by Ar-Ar age determinations on intrusive ultramafic melilithic rocks in the diatremes of Dolní Falknov (≤ 68.34 ± 0.33 Ma) and Stožec (68.80 ± 0.85 Ma). Detailed geological mapping of both volcanic structures enabled to clearly demonstrate typical diatreme breccia only in the Dolní Falknov diatreme. In contrast, mapping of the Stožec volcanic structure 5 km to the northeast only revealed an intense red-brown coloured diamictite deposit. This diamictite also occurs in the top of the Dolní Falknov diatreme fill as separated clods and is interpreted as a collapse breccia. The diamictite as well as the diatreme breccia contain numerous rounded pebbles of different lithologies with diameters of up to 0.5 m. Some of these pebbles probably come from Permian rocks (Rotliegend) and indicate a multi-phase redeposition history. These could be erosion products from the Lausitz Block, which is located 2.5 and 5 km north of the two diatreme structures. The Permian sediments eroded here were later rounded off before being redeposited as terrestrial (red) sediments in the uppermost Upper Cretaceous (Campanian–Maastrichtian). These deposits have only been preserved due to their sheltered position within the pre-rift diatreme structures.