The greater Paris basin lies between several Herchynian uplands: Armorica, the Ardennes, the Vosges and the Massif Central. It includes Chalk plateaux in the north, scarplands in the east, both converging with the central Paris basin (the Île de France). To the south is the middle Loire valley. In the north the elevation of the extensive Chalk plateaux rarely exceeds 200 m. The extensive plateau surfaces might relate to long periods of erosion during the Neogene, and could therefore be the equivalents of such surfaces on the Hercynian massifs. Further east the sequence of Mesozoic rocks that dip towards the basin centre form a series of arcuate belts aligned more or less north-south, with pronounced scarp slopes facing east. The central Paris basin comprises a virtually complete sequence of Cenozoic strata from Palaeocene to Pliocene in age, unconformably resting on the Chalk of the outer Paris basin. The sequence is gently folded into an asymmetric basin centred on Paris. In the east, above basal sands, the Palaeocene-Eocene Calcaire de Brie forms a pronounced east-facing escarpment, known as the “Falaise de l’Île de France. From the central Paris basin the terrain slopes gently south towards the Loire valley. Away from the margins of the Massif Central the relief of the middle Loire valley is very subdued. The distinctive features all relate to the river valleys and the modern river channels. The Loire itself shows several reaches with meandering channel patterns, but progressively downstream braiding becomes more important.