ABSTRACT The Petit Marais site at La Chaussée-Tirancourt is located at the confluence of the Somme valley and a little stream called the Aeon. Some Mesolithic levels from the Boreal are associated with alluvial sediments which are sealed by peat dated from the Atlantic period. Thousands of //- thic and bone remains attest to the numerous activities practised on the site. Five Mesolithic pits have been excavated. Many radiocarbon da- tings bring to the fore an important diachronism between those structures. Pit number 1 contained many burnt human bones. Pit number 4 is a burial place. The skeleton is that of an adult male. He had a particularly robust skull like the Téviec and Hoëdic individuals and was tall. The organisation of the bone rem...