ESR DATING BOVID TEETH FROM THE NEANDERTHAL LAYER AT LA FERRASSIE, FRANCE

In 1902-1923, Peyrony and Capitan excavated the archaeologically rich deposits from the rock shelter at la Ferrassie, France. Among the finds were seven Neanderthal skeletons interpreted to represent a cemetery with intentional burials. This site has yielded the largest well preserved collection of penecontemporaneous Neanderthals from Europe. La Ferrassie I, a nearly complete male skeleton, is often used as the "typical" Neanderthal. Bordes defined the large associated lithic collection as the type for the Ferrassie variant of the Mousterian. Due to primitive excavation techniques and sparse excavation reports, attempts to match Peyrony's profile which yielded the skeletons with the later witness section some 16 m away have proven controversial. Because the area around the skeletal material was excavated completely, and part of the pit later filled in to enable tours to visit the site, no modern dates have ever been attempted for the layers which housed the skeletons.

The rock shelter at la Ferrassie contains a series of matrix- and clast-supported conglomerates deposited at the edge of a karstic escarpment. When occupied by Neanderthals, it would have been at least partially covered by a limestone overhang. Photos from the 1912 excavation show the La Ferrassie I skeleton surrounded by large amounts of pebble-sized éboulis. In 1912, the excavation trench only 2 m wide, although it was later widened considerably. The site report listed Rangifer, large bovids, and cervids in the Mousterian layer, which also housed the skeletons.

The AMNH collections from 1912 yielded two large bovid teeth from the Mousterian layer at La Ferrassie, which must have derived from within 2.0 m of the adult skeletons and from the layer which yielded the skeletons. These two teeth were dated using standard and isochron ESR. The teeth show less than 0.5 ppm U in the enamel and 3-5 ppm U in the dentine. Accumulated doses for the two teeth average 18.5 ± 0.2 Gy and 22.1 ± 0.5 Gy. Assuming 50-60% éboulis in the sediment around these teeth gives ages, 55 ± 2 ka to 61 ± 5 ka. These ages correlate well with the later phases of OIS 4 or the earliest in OIS 3, when climates began to show much more frequent large temperature swings.