The importance of U-series disequilibrium of sediments in luminescence dating: A case study at the Roc de Marsal Cave (Dordogne, France)

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• 作者：Pierre Guibert ; Christelle Lahaye ; Franç ; oise Bechtel
• 关键词：U-series disequilibrium ; Annual dose ; Luminescence dating ; Low background gamma spectrometry ; Alpha spectrometry
• 刊名：Radiation Measurements
• 出版年：2009
• 出版时间：March 2009
• 年：2009
• 卷：44
• 期：3
• 页码：223-231
• 全文大小：359 K

文摘

A multidisciplinary study of the Roc de Marsal Cave gave us the opportunity to re-examine the known problem posed by U-series disequilibria in sediments in the field of palaeodosimetric dating. Apart from burnt flints and heated limestones, the material being dated, THAT IS our principal concern here, is made of burnt sediment samples collected from a reddish layer that forms the very base of the Roc de Marsal Mousterian sequence (Couche B). U-series disequilibria of long life nuclides in sediments were observed: as a general trend, the activity of ²³⁸U is greater than that of ²²⁶Ra. Important discrepancies in age determination can occur according to the origin of the disequilibrium and its kinetics. To characterise these ancient modifications of radioactivity and constrain the range of possible variations of annual doses, a statistical study of ²³⁸U, ²²⁶Ra and ²³²Th activities, measured by gamma spectrometry, was carried out. It shows that the sediment was mainly enriched in mobile uranium. This conclusion is in accordance with the results of complementary measurements of ²³⁰Th and ²³⁴U performed by alpha spectrometry. On the kinetics side, two models of time-variation of U and daughter concentrations are compared, taking experimental data into account. A detailed presentation of the methodology and the method of calculation of dose rates, and particularly time-averaged dose rates in such a situation, is given.