Soot traces are witnesses of past human activities. They can sometimes be noticed on the walls and vaults of caves and rock shelters, sometimes also inside speleothems. These deposits resulting from anthropogenic fires prove to be a suitable material for micro-chronological studies. The microscopic analysis of parietal carbonated crusts of various ages, from Grotte Mandrin (Middle Palaeolithic from about 100 ka till early Upper Palaeolithic around 42 ka BP) and from the Balma de la Margineda (late Upper Palaeolithic) shows that they have preserved the trace of multiple occupations. These latter can be linked to the archaeological units recognised on excavation field. The MNO (Minimum Number of Occupations) recorded at high temporal resolution for each archaeological level are usually high. These attest the cumulative nature of archaeological units and invite to rethink the following concepts of “archaeological floor” and “palimpsest” vis-à-vis spatial studies in caves and rock shelters. Each unit records a different number of occupations and shows its own rhythmicity in the succession of occupations. By retracing occupations chronicles of each archaeological level, possibility for studying mobility of passed human groups can also be raised.