PORTABLE OSL READER APPLICATIONS FOR THE STUDY OF SEDIMENTOLOGICAL PROCESSES IN VOLCANIC DEBRIS FLOWS

The development at the Scottish Universities Environmental Research Centre of a portable reader of optically stimulated luminescence (OSL) has enabled the measurement of OSL in the field for applications other than dating. Here we use the portable reader to study sediment entrainment processes in volcanic debris flows (lahars). The case study is located on Popocatépetl volcano, Mexico, focusing on the three most recent lahars on the volcano’s NE flank. The first of those lahars took place >1.3 ka ago and the second and third in 1997 and 2001, respectively. Sediment samples were extracted through the full thicknesses of the lahar deposits from different sites along their flow paths. In the portable OSL reader, polymineral and polygrain-size samples were stimulated in the blue and infrared wavelengths and the total photon counts from each sample were analyzed to assess changes in luminescence along these flow paths. An increase in the luminescence signals at a site, relative to the luminescence at the next site upstream, has been interpreted to reflect the incorporation or bulking of old material into the flow. The study demonstrates that using luminescence signals in this way can be helpful for the study of depositional processes in sediment-laden flows.