Archeometry of Five Pleistocene Sites as Inferred from Uranium and Thorium Isotopic Abundances in Travertine

Abstract

The U/Th dating method has been applied to five archeological sites in France. The U/Th method relies upon the co-precipitation of uranium with calcium carbonate in speleothems formed in caves. Because 230Th forms in the calcite from the decay of 234U a radiometric clock is begun in the newly deposited calcite. Dates are derived from measuring the isotopic abundances of the uranium and thorium in the calcite. For many archeological samples, preroasting of the sample before analysis is necessary to improve the yields. Normally, relative dates for archeological sites are derived from the comparison of paleoclimatic interpretations determined from sedimentological, faunal, and palynological studies of the cave sediments with global climatic records. These methods have established that the Mousterian culture and Neanderthals appeared in Europe at the beginning of the Würm, 80 Ka BP. Absolute dates determined for samples from Lachaise, Montgaudier, Pech de l'Aze, Abri Vaufrey, and Grotte 13, where archeological or faunal material is associated stratigraphically with speleothems sampled, have established that there were several regional climatic phenomena experienced in southern France. These events are dated at 80 to 120 Ka BP, interpreted to be the Riss/ Würm interglacial, and at 38 to 50 Ka, interpreted to be the Würm I/II interstadial. Furthermore, archeological materials and human skeletal remains associated with these sites and the speleothems therein, have proven that the Nean~erthals must have evolved prior to 150 Ka BP, but that they did not develop their Mousterian culture until about 125 Ka BP.