The status of ravine-like incisions in the dry valleys of the Pays de Thelle (Paris basin, France)

In the Pays de Thelle, France, ravines often cut the bottom of local chalk dry valleys. Morphometric and sedimentological analyses are used in an attempt to reconstruct the palaeoenvironments during the morphodynamic evolution of these small dry valleys. As in other Paris basin districts, the dry valleys were formed during periglacial Quaternary periods. However, some of the ravines look like fluvial incisions that have began since the Subboreal and result more from recent uplift of the Bray anticline than from human activities alone. Present agricultural practices, which are not in accordance with respect for the environment, contribute to the surface runoff that produces muddy floods along the dry valleys, but they are not thought to be the cause of the ravines.