Optically stimulated luminescence dating of a stratigraphic Late Glacial-Holocene sequenze in the Po plain (Bubano quarry, Bologna, Italy)

Quartz and K-feldspars from an exposed 14-m-thick undisturbed succession of silty-clay Late Glacial–Holocene sediments in the Po plain (Bubano quarry, Bologna province, Italy) were optically dated. For part of the sequence, three radiocarbon ages and palynological dating provide an independent age control. The separation procedures, whose effectiveness was checked at each step by means of quantitative X-ray powder analysis (QXRPD), and single-aliquot regenerative dose protocols adopted, are discussed. In general, the quartz optically stimulated luminescence (OSL) ages are systematically younger than those obtained with feldspars, probably due to the presence of medium component in the OSL decay. The evidence of contribution from the low-sensitivity light traps has been checked using LM-OSL measurements, and the equivalent doses have been calculated considering only the contribution of fast components. Moreover, a residual presence of feldspars in the quartz-separated fraction, even if not detected by QXRPD, could account for the observed underestimation. The OSL ages were consistent with the radiocarbon chronology.