The composition of the detrital fraction of the Nicolet River Formation suggests that the rocks of the Autochtonous and the External Domains of the Quebec Appalachians were mostly derived from the sedimentary nappes of the External Domain. The contribution from the metamorphic nappes and ophiolites of the Internal Domain was minor but it indicates that the dynamothermal metamorphism had been completed by the end of the Middle Ordovician (C. spiniferus Zone). Piling up of the nappes, each one progressively richer in feldspar, produced a source of high relief subject to subaerial erosion. The vertical evolution observed in the flysch probably results from tectonic activity at the source area rather than from deep-sea fan progradation. The stratigraphic relationships evince that the deposit accumulated in basins controlled by a series of horsts and grabens.