A preventive excavation prior to the extension of a quarry revealed a Mesolithic concentration in the valley of the Thérain. This wide alluvial plain was at that time a mixture of gravel mounds, channels and peat bogs. The Prehistoric site was situated close to a channel about sixty metres from a steep chalk bank.  The finds are few, but they include some well-preserved animal remains from roe deer and aurochs, and a lithic industry restricted to products of full debitage and to microburins. The surface of the excavation however is too limited to justify any decision between the hypotheses concerning the function of the site. It may have been a specific working area connected with a dwelling, or a place used for butchery and the maintenance of hunting weapons close to a slaughter area. The typo-technological characteristics of the lithic industry would support an attribution to the local Early Mesolithic. Traduction : Margaret & Jean-louis CADOUX