ESR DATING IN A MOUSTERIAN LAYER AT GROTTE DU BISON, ARCY-SUR-CURE, YONNE, FRANCE

A partially collapsed cave with an extant gallery and another 30 m² of archaeological deposits out front, Grotte du Bison opens south 6 m above the modern Cure River, a meandering river incised into Jurassic limestone. A sequence of clast- and matrix-supported conglomerates house at least eight archaeological layers, some of which correlate with layers found next door at the Grotte du Renne. In Grotte du Bison, Mousterian and Châtelperronian layers have produced hearths, ochre, manuports, and lithics, including bifaces, scrapers, cortical and retouched flakes. Levallois technology dominated the Charentian Mousterian industry, made mainly on flint and silcrete. Most cores and tools, mainly sidescrapers and endscrapers, were found in the main gallery or outside. Roughly equal numbers of reindeer, horse, and bovid fossils occur, plus cave bear, mammoth, roe deer, red deer, birds, fish, lemmings, susliks, some larger herbivores, and carnivores. Faunal analyses from > 8,000 bones, including ~ 100 bird bones, suggest a cold steppe with some forest. Preliminary pollen analyses suggest very few trees, only scattered willow and pine, with many cold steppe grasses and chenopods. The Mousterian layers have yielded 20 Neanderthal remains, including a partial adult maxilla, 13 isolated permanent and deciduous teeth from at least five individuals, ranging in age from an infant 2-4 years to adults.

From Couche J in the Mousterian layers, 28 independent subsamples from four Equus teeth were ESR dated to enable isochron analyses. The external dose rates for each tooth were determined by measuring the radioactivity in associated sediment samples, and by assuming a time-averaged cosmic dose given the sample's varying amount of roof cover since its deposition. U in the enamel ranged from 0.06-0.50 ppm, while dentinal U ranged from 2.6-20.6 ppm. Isochron analyses suggest that some recent U remobilization has affected the teeth. Nonetheless, the mean LU ages correlate well with early Marine (Oxygen) Isotope Stage 3.