Luminescence dating of scoria fall and lahar deposits from Somma-Vesuvius, Italy

Luminescence dating has been applied to scoria and lahar deposits from Somma-Vesuvius, Italy. Samples include scoria from the AD472 and 512 (or 536) eruptions and lahar deposits. In order to find a stable luminescence signal which is less affected by anomalous fading, infrared stimulated luminescence (IRSL) signals at elevated temperatures after bleaching with IR at 50 degrees C (termed post-IR IRSL; pIRIR) were tested at different preheat and elevated stimulation temperatures. The fading rates of both IRSL and pIRIR signals reduced dramatically with increasing preheat and pIRIR stimulation temperatures. A pIRIR signal measured at 290 degrees C after a preheat at 320 degrees C (60 s) and an IR stimulation at 50 degrees C (100 s) was selected to calculate the equivalent dose (D-e). The gamma spectrometry results indicate that the U-series nuclides are not in equilibrium and there is a large Ra-226 excess. The dose rates and ages were calculated by assuming a Ra-226 excess (over its parent Th-230) at deposition, and that this unsupported excess then decayed to the present level. The resulting luminescence ages of the two scoria samples agreed with the expected ages, and the ages of the lahar deposits indicate that they are associated with the AD1631 eruption. (C) 2013 Elsevier B.V. All rights reserved.