Optical dating of late quaternary coastal deposits in northwestern Portugal

The northwestern coastal zone of Portugal between Mondego cape and Minho River preserves a series of fluvio-aeolian, lagoonal, and dune formations that are archives of evolution during the late Pleistocene and Holocene. The existing chronology of these formations is based mainly on radiocarbon dating of in situ organic materials.

In this study, we present the results of optically stimulated luminescence (OSL) dating of these formations and discuss their implications for the existing chronostratigraphy, climate, and neotectonic changes in this area since the late Pleistocene. Three major periods of aeolian activity have been identified based on the OSL ages and are bracketed to 25-14 ka, 9.9-3.4 ka, and 1.4-0.1 ka.

These OSL ages suggest intense sand deposition during oxygen isotope stage 2, the midHolocene, and the Little Ice Age. The dune ages in the last 500 years provide temporal constraints on the initiation of coastal erosion in the area. Further, the chronostratigraphic correlations suggest tectonic uplift in the coastal sections, between ca. 17 ka and 14 ka, and erosion due to eustatic sea-level rise.