RADIOCARBON AND BLUE OPTICALLY STIMULATED LUMINESCENCE CHRONOLOGIES OF THE OITAVOS CONSOLIDATED DUNE (WESTERN PORTUGAL)

The dune of Oitavos, the underlying paleosol, and Helix sp. gastropod shells found within the paleosol were dated using a combination of radiocarbon and blue optically stimulated luminescence (OSL). The organic component of the paleosol produced a significantly older age (similar to 20,000 cal BP) than the OSL age measurement (similar to 15,000 yr), while C-14 age measurements on the inorganic component and the gastropods produced ages of similar to 35,000 yr and similar to 34,000 yr, respectively. Rare-earth element analyses provide evidence that the gastropods incorporate geological carbonate, making them an unreliable indicator of the age of the paleosol. We propose that the C-14 age of the small organic component of the paleosol is also likely to be unreliable due to incorporation of residual material. The OSL age measurement of the upper paleosol (similar to 15,000 yr) is consistent with the age for the base of the dune (similar to 14,500 yr). The younger OSL age for the top of the dune (similar to 12,000 yr) suggests that it was built up by at least 2 sand pulses or that there was a remobilization of material at the top during its evolution, prior to consolidation.