The formation of thick piles of flysch-like sediments needs the existence of narrowed seas, active denouement of neighbouring continents, and generalized marginal subsidence. These conditions are present during the initial and final stages of Wilson’s perceptive cycle. In this context, the Late Precambrian flysch of the Iberian Massif must be related to the initial rifting, whilst the Culm of southwestern Iberia was accumulated during an episode of Upper Palaeozoic subduction that remained active after the impingement of Iberia against North America. Culm sediments shed from the uplifted collision zone and fed into a remnant ocean that remained at the nonsutured southern border of Iberia. This model of synorogenic flysch formation has been described elsewhere for similar plate arrangements. On other grounds this model provides a framework that explains the different structural and magmatic trends of the Ossa-Morena Zone (near the active margin) in the context of the rest of the Massif (basement reactivation). In addition to this, it seems to support a partly primary origin for the Iberian arc versus a secondary origin.