ESR as a method for the characterization of alluvial sediments
Résumé
The possibility of using the parameters involved in the ESR dating of optically bleached quartz grains in a purpose of source determination was checked. In that aim, samples previously taken in different sedimentary formations of the Middle Loire Basin (Central France) and dated by ESR have been observed. First discrimination was made using the thorium and potassium content in the sediments obtained by gamma spectrometry. The plot of these 119 data on the Th/K Schlumberger diagram clearly demonstrated that it was possible to discriminate the clays associations included in the sediment from which the dated quartz are extracted. Clay's nature could then be indicative of the geological nature of the substratum of rivers from their sources. Second discrimination was made using the ESR intensities calculated from Al, Ti–H and Ti–Li paramagnetic centres on 18 samples. It appears that the combination of the non-bleachable aluminum trap (DAT) saturation intensity and the Ti–H/Ti–Li ratio intensities make possible the discrimination of the two main sources of the sediment: Massif Central and Paris Basin. More deeply, The Ti/OBAT (Optically bleachable aluminum traps) intensities made possible the discrimination of quartz grains of different geological sources or with different geothermal history within the Massif Central group.