Lower Devonian monomict-quartzose coarse-grained clastics near Brno (on the Cerveny kopec Hill) are interpreted as the deposits of an alluvial fan built up mainly by catastrophic sheetfloods. The main sources were probably granites and gneisses, other components were derived from rhyolites, older siliciclastic sediments and low-grade metamorphic rocks. Abundant presence of muscovite reflects some role of an exotic source area. Rapid uplift, erosion dominated by mechanical weathering and multiple redeposition are supposed within the drainage basin. The flat alluvial fan was only slightly reworked and eroded during subsequent non-catastrophic overland flows (secondary processes). A relatively mature stage of the evolution of the alluvial fan and drainage basin was accepted. A continental extensional basin represents the most probably depositional setting of the studied deposits.