Optically stimulated luminescence dating of Holocene relict foredunes, Guichen Bay, South Australia

Optically stimulated luminescence (OSL) dating of quartz sand (106–150 or 150–200 μm) in bioclastic carbonate–quartz sediments sampled from coastal relict foredunes (beach ridges) was undertaken to evaluate the utility of the OSL method for studies of dune dynamics and to quantify rates of coastal progradation. Twelve sediment samples from a 4 km transect across a Holocene embayment fill at Guichen Bay, South Australia, were measured for their luminescence characteristics. Apart from one age inversion attributed to recent disturbance associated with mining, the OSL ages are in sequential order when considered in the context of their associated error terms. The OSL ages indicate an extremely rapid initial phase of sedimentation (i.e. 1600 m within a few hundred years, approximately 5 ka ago) followed by a constant rate of progradation for the past 4 ka of 0.39 m/a, with a high level of association between distance across the embayment fill and luminescence age for this time interval. An average rate of dune development of one dune every 80 yr from 3900 yr ago to the present day is apparent. The OSL ages for the late Holocene indicate that the present beach state is largely in equilibrium with sediment supply.