LUMINESCENCE DATING OF HOLOCENE BEACH-RIDGE SANDS ON THE YUMIGAHAMA PENINSULA, WESTERN JAPAN

We applied infrared stimulated luminescence (IRSL50) and post-infrared (post-IR) IRSL150 dating to K-feldspar sand obtained from Holocene beach ridges on the Yumigahama Peninsula, Japan, to investigate the rate of progradation of the beach, which has been affected by 17-18th century iron mining in a local river catchment. All samples showed higher equivalent doses for the post-IR IRSL signal. Fading tests indicated that IRSL yielded relatively high g-values (11-13%/decade), while post-IR IRSL yielded negative g-values (-5 to -8%/decade). The corrected IRSL age of the oldest sample, 8.1 +/- 1.3 ka, was slightly overestimated with respect to its expected age of 5-6.7 ka. The corrected age is highly dependent on the g-value, which if slightly inaccurate would have caused the overestimate. The uncorrected post-IR IRSL ages were underestimated, and we consider that the post-IR IRSL signal faded. However, given the negative g-values, application of an appropriate fading correction was not feasible. The corrected IRSL ages of the younger samples, coupled with an assumption of residual dose, roughly agreed with the historical shoreline changes, indicating that the rate of shoreline progradation increased markedly during the recent period of mining-related enhanced sediment discharge.