10 B e dating of the M ain T errace level in the A mblève valley ( A rdennes, B elgium): new age constraint on the archaeological and palaeontological filling of the B elle‐ R oche palaeokarst

It is still disputed whether very old archaeological and palaeontological remains found in the B elle‐ R oche palaeocave (eastern B elgium) pertain to the E arly (∼1  M a) or M iddle (∼0.5  M a) P leistocene. Here, in situ ‐produced cosmogenic 10 B e concentrations from a depth profile in nearby sediments of the B elle‐ R oche terrace ( A mblève M ain T errace level) are used as an indirect solution of this chronological issue. The distribution of 10 B e concentrations in the upper 3 m of this profile displays the theoretically expected exponential decrease with depth. Assuming a single exposure episode, we obtain a best fit age of 222.5±31 ka for the time of terrace abandonment. However, below 3 m, the 10 B e concentrations show a marked progressive increase with depth. This distinctive cosmogenic signal is interpreted as the result of slow aggradation of the fluvial deposits over a lengthy interval. Modelling of the whole profile thus suggests that the onset of the terrace formation occurred at around 550 ka, with a sediment accumulation rate of ∼20 mm ka −1 . Based on two slightly different reconstructions of the geomorphic evolution of the area and a discussion of the temporal link between the cave and M ain T errace levels, we conclude that the fossil‐bearing layers in the palaeokarst pertain most probably to MIS 14–13, or possibly MIS 12–11. This age estimate for the large mammal association identified in the B elle‐ R oche palaeokarst and the attribution to MIS 14–13 of a similar fauna found in the lowermost fossiliferous layers of the C aune de l' A rago ( T autavel) are in mutual support. Our results therefore confirm the status of the B elle‐ R oche site as a reference site for the C romerian mammal association in NW E urope.