The excavation carried out before the construction of a sewage treatment plant in the Oise valley at La Croix-Saint-Ouen has allowed the study of a significant stratigraphy covering mainly the third millenium BC. It is made up with alternate levels of river banks and alluvial deposits wich contain artefacts either in a position of refuse or included in settlement levels. The major interest of this site is the discovery at the base of an ancient bank of an organic level which has been explored over a 20 square meter surface. Besides organic remains, plant fragments, worked and naturally occuring pieces of wood, this layer has revealed an adze shaft and a broken bow. Ceramic flint and bone artefacts discarded with the wood are all dated from Later Neolithic period which was confirmed by dendrochronology.