The recent discovery (2009) and excavation of the open-air site of Ormesson (Seine-et-Marne e France) was initially intended to document a Gravettian occupation floor dated around 29,000 cal. BP and related to a preferential bison hunt. Whilst checking the thickness of the loess in which the Gravettian level was found, several other prehistoric settlements were discovered (Chatelperronian, Middle Solutrean) including two units attributed to the Middle Palaeolithic. One, level 4, seems to be particularly wellpreserved. It occurs between 1 and 3 m below the main Upper Palaeolithic occupation. The lithic industry from level 4 belongs to a single kind of reduction sequence: the Discoid method. The freshness of the material and the presence of bone fragments attributed in part to horse support a general good state of preservation of this occupation. The Mousterian remains seem to cover at least 500 m 2 , as currently estimated. Even more exceptional is the close spatial relationship between the discoid industry, the bone pieces, remains of fireplaces and especially the numerous fragments and nodules of red colouring materials. These were brought to the site where they were utilised by the Mousterians. The used surfaces show indisputable scraping traces and facets. These recent discoveries will certainly contribute to the debate on the cognitive capacities of nearly the last representatives of the Middle Palaeolithic, and the complex stratigraphy will allow comparisons between the different periods.

quatre loess anciens se superposent, avec quatre sols interglaciaires intercalés : Elbeuf I (Eemien), Elbeuf II, Elbeuf III et Elbeuf IV. Le sol le plus ancien (Elbeuf IV) est fossilisé localement par une couche de sables blancs alluviaux et par un tuf calcaire intégrant une association malacologique interglaciaire à Lyrodiscus, maintenant considéré comme marqueur biostratigraphique du stade isotopique 11. L'âge du complexe Elbeuf IV, sables et tuf (environ 400 ka) est en accord avec la stratigraphie et les nouvelles datations OSL. Au-dessus du tuf, au début d'une nouvelle sédimentation loessique (stade isotopique 10) un niveau d'occupation rapportable à l'Acheuléen a été mis au jour. Ce dernier est actuellement le plus ancien sol d'occupation étudié en Normandie. Il correspond à une implantation de bord de berge caractérisée par quelques restes de macrofaune mal conservés et de nombreux artefacts qui témoignent d'opérations de débitage et de façonnage d'outils (biface et outils sur éclat).

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