ESR DATING AT PRADAYROL, LOT, FRANCE: CONSTRAINING THE AGE FOR THE MIDDLE PLEISTOCENE BONE-BEARING LAYER, ITS MIDDLE PALEOLITHIC ARTEFACTS AND HOMINID INCISOR

In 1999, a hominid tooth associated with extinct Middle Pleistocene fauna was discovered in Layer 2 at Pradayrol, Lot, France. Near Caniac-du-Causse, the Pradayrol site occurs within a large abri with fill reaching 10-15 m. A test trench has been excavated through four stratigraphic units, two of which have yielded mammalian teeth for dating. More than 1000 Middle Paleolithic artefacts have been found at Pradayrol, mostly sidescrapers made from quartzite or flint and flaking debris found in Layer 2A. The small tool size suggests in situ production and raw material parsimony. This Denticulate Mousterian tool kit resembles that from La Borde.

The hominid upper right permanent incisor compares in size and features with the Neanderthal teeth from La Chaise-de-Vouthon. Also found in Layer 2A were numerous extinct Middle Pleistocene fauna, including Dicerorhinus mercki, Equus mosbachensis, Canis etruscus, and Ursus deningeri, all suggesting an age > 150 ka. In order to determine an absolute age, four bovid teeth from Layer 2A were dated by standard and isochron ESR. Ages from 18 independent ESR analyses suggest an average LU age for Layer 2A of 330 ± 5 ka, which correlates with earliest Oxygen Isotope Stage (OIS) 9. Isochron analyses suggest that U remobilization in the teeth occurred recently.

In 2005, new excavations revealed two more layers with multiple recognizable horizons below Layer 2A. Fauna from Layer 4B included Ursus deningeri, porcupine, hyenae, Canis sp., Marmota, equids, cervids, bovids, rodents, and many bats. Several enamel fragments and two partial ungulate teeth from Layer 4B were dated using standard ESR. Accumulated doses and U concentrations for the teeth from Layer 4B resemble those from Layer 2A. The sediment, however, shows more variation in radioactivity and sedimentary dose rates. Preliminary results from 10 analyses indicate that the ages for teeth average 330 ± 15 ka. This suggests that Layer 4B also correlates with the earliest phases of OIS 9.