Soot marks can be noticed in cavities’ concretions. These deposits, generally ignored, are perfectly suitable material for micro-chronological study of hominine activities in a site. In Grotte Mandrin (Mediterranean France) microscopic observation revealed parietal sooted crusts kept track of many occupations, which can be linked with archaeological units. Minimum Number of Occupations and occupations chronicles can be built out of these crusts. MNO, usually high, attest of the cumulative nature of each archaeological unit. This pioneering study shows that sooted concretions analysis provides high temporal resolution archaeology and allows here to rethink the MP/UP transition with an unmatched temporal resolution. Note : This talk is presenting a new micro-chronological method through application on a site. We show that at the Grotte Mandrin (Mediterranean France), a very short time separates the first Upper Palaeolithic groups’ occupations from those of the last Mousterians.