Résumé
The excavation of the Middle Palaeolithic site of Mauquenchy (Seine-Maritime) led to the discovery of well preserved archaeological levels in a grey forest soil attributed to the marine isotopic stage (MIS) 5a. This soil contains two archaeological levels, one at the bottom (Wa2), the second in its upper part (Wa1). Both sets contain archaeological heated flint dated by thermoluminescence (83.7 +/- 7.6 ka for Wa2 and 77.6 +/- 7.2 ka Wa1). These ages provide for the first time a precise timing for this soil that had previously been assigned to MIS 5a on the basis of its interstadial signature.