Depositional environment of the "Old Red" sediments in the Brno area (south-eastern part of the rhenohercynian zone, Bohemian Massif)

Lower Devonian monomict-quartzose coarse-grained elastics near Brno (on the Cerveny kopec Hill) are interpreted as the deposits of an alluvial fan bui lt up mainly by catastrophic sheetfloods. The main sources were probably gr anites and gneisses, other components were derived from rhyolites, older si liciclastic sediments and low-grade metamorphic rocks. Abundant presence of muscovite reflects some role of an exotic source area. Rapid uplift, erosi on dominated by mechanical weathering and multiple redeposition are suppose d within the drainage basin, The flat alluvial fan was only slightly rework ed 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.