Evidence for Pleistocene wet aeolian dune and interdune accumulation, S. Pedro da Maceda, north-west Portugal

Outcrops and cored/counter-flushed boreholes in the coastal area between Espinho and Aveiro (north-west Portugal) were investigated to reconstruct the changing patterns of sedimentation during the Late Pleistocene-Holocene. To obtain a common comparison basis, the grain-size data from outcrop and borehole samples were analysed. The outcrops and the cored parts of the boreholes were dated by radiocarbon and optically stimulated luminescence. The results show that, on top of pebble-rich beds of fluvial origin, a wet aeolian dune and interdune environment was active during the later part of the Pleistocene, turning to dry aeolian at the transition to the Holocene. The data indicate also that aeolian accumulation was controlled by vegetation changes (climate) and groundwater table fluctuations. During the Holocene, a podzol formed on the Pleistocene dunes and extensive vegetation precluded major aeolian accumulations. Remobilization of sand started again because of human deforestation and - last but not least - the Little Ice Age.