The Bau de l'Aubesier is a large rock shelter in the Gorges de la Nesque, Monieux, Vaucluse, France (44° 05' N, 5° 21' E). Although previously investigated (6, 7), S.L. has excavated the site since 1987 and discovered Middle Pleistocene human remains in 1994 and 2000.
The upper portion of the Pleistocene deposits (13 m thick over >520 m2) consists principally of Late Pleistocene levels containing Middle Paleolithic archeological remains (Fig. 1). The lower portion of the site, with a thickness > 10 m, derives primarily from the Middle Pleistocene (levels G to K). Its succession of stratified deposits containing limestone éboulis, blocks, and slabs is interspersed with a nonsystematic matrix of fine interstitial calcareous sediment, much of which is brecciated in layer G. The archeological layer H-1, 55 cm thick, consists of a high density of faunal remains, lithics, wood charcoal, and ash in a highly organic sediment, and the lithics and faunal remains are burnt to different degrees. On the basis of the lithostratigraphy, there appears to have been a chronological hiatus between layer H-1 and the underlying I series.
The layers with human remains, I-2, I-3, and K-1, yielded high concentrations of large herbivore remains and flint artifacts, each a palimpsest of repeated phases of site occupation. Their lithic assemblages are typical Mousterian with abundant sidescrapers, Levallois flakes, and especially Levallois blades, similar to those from a growing number of late Middle Pleistocene Middle Paleolithic site levels containing laminar assemblages (8).
The fauna of level I includes Ursus arctos, Dicerorhinus hemitoechus, Equus mosbachensis, Sus scrofa, Cervus elaphus, Dama dama, Capreolus capreolus, Megaceros giganteus, Bos primigenius, Hemitragus cedrensis, and Rupicapra rupicapra, with Bos (43%) and Equus (31%) dominating. Well recognized in the Middle Pleistocene, E. mosbachensis in particular indicates an age no later than oxygen isotope stage (OIS) 6 (9); it is succeeded by E. cf. taubachensis in the overlying layer H-1, which could refer it to OIS 5e (9). The form of C. elaphus can be assigned to OIS 6. D. dama is present from level J and higher, indicating a post-Holsteinian (post-OIS 9 or 11) age for these levels (9). H. cedrensis corresponds to an age in OIS 7, 6, or 5e (9).
Thermoluminescence dating was performed on six heated flint samples from layer H-1, following the experimental procedures previously described (10, 11). To evaluate the external -dose rate, because it contributes 50% to the total accumulated dose, five CaSO4 dosimeters were implanted in the same or adjacent squares for 1 year, and - and -spectrometry was performed in the laboratory on samples of the fine component of the sediment. In principle, the results obtained with dosimeters reflect the actual environmental -dose rate more accurately, because the sediment is a mixture of large and small components. However, the -spectrometry revealed the presence of a disequilibrium in the 238U decay chain, and the -spectrometry indicated the loss of 226Ra. Therefore, the external -dose rate, as measured with the dosimeters, might not have been true for the entire period of burial in the site. Two models have to be used to allow the calculation of minimum and maximum age estimates for layer H-1, because the timing of the (re-)occurrence(s) of the disequilibrium cannot be established. The minimum age is determined assuming the occurrence of a single, recent 226Ra loss. The external -dose rate is thus calculated on basis of the concentration of 230Th (full natural uranium chain) and corrected for the relative contribution of the fine sediment to the total external -dose rate from all components. Assuming a constant loss of 226Ra since deposition, the maximum age can be calculated by using the external -dose rate as measured by the dosimeters.
The results of the two models for the six samples give an average minimum age estimate of 169 ± 17 thousand years (ka) and an average maximum one of 191 ± 15 ka for layer H-1. Using the 2- range of these age estimates, the flint samples were heated either in OIS 6 or 7. The biostratigraphic indicators for layer H-1 are somewhat younger than these results. The human remains from layer I2, I-3, and K-1 derive from slightly deeper in the stratigraphic sequence than later H-1, and they therefore date to the later Middle Pleistocene.