LUMINESCENCE DATING OF YOUNG COASTAL DEPOSITS FROM NEW ZEALAND USING FELDSPAR

A new measurement protocol has been tested on K-feldspars from Whanganui Inlet and Parengarenga Harbour, New Zealand. A Single Aliquot Regenerative (SAR) dose protocol, using two successive infrared (IR) stimulations (post-IR IR SAR protocol) is setup for these young (< 1000 years) coastal sediments. Significant anomalous fading (g(2days) = 7 %/decade) is observed using the conventional IR signal measured at 50 degrees C. In contrast, the fading rate of the IR signal measured at elevated temperature (150 degrees C) after the IR stimulation at 50 degrees C (a post-IR IR signal) is not significant (g(2days) <= 1 %/decade). Surprisingly low residual infrared stimulated luminescence (IRSL) signals were observed for a surface sample, suggesting that accurate ages as young as similar to 50 years can be obtained for these recent deposits. IRSL ages ranging between 48 +/- 6 years and 1050 +/- 50 years are obtained from six samples, indicating that sediment accumulation has occurred at the two sites during the last millennia, despite a falling trend in relative sea-level in Whanganui Inlet and a stable relative sea-level at Parengarenga Harbour.