Mapping and chronology of coversands and dunes from the Aquitaine basin, southwest France

Abstract

New stratigraphic (including GPR profiles) and chronological data provide a detailed understanding of the emplacement of aeolian sands in the Aquitaine basin (SW France). The main phase of coversand deposition ranges from 25 ka to 14 ka. The ages cluster around two periods that match Heinrich events (He-2 and He-1) and reflect increased sedimentation in response to aridification and high mean wind speeds. The age distribution is skewed toward recent phases, which likely results from continuous sand recycling. The dunes currently visible in the landscape were formed during the Younger Dryas/very early Holocene and the historical period. The Younger Dryas dunes are inland low parabolic dunes that have been strongly degraded. Only the last phases of the progression of the coastal dunefield are preserved because of coastal erosion. Two depositional phases have been identified, the Dark Ages Cold Period and the Little Ice Age, which correspond to phases of increased storminess already known from the coastal record in Europe. The Dark Ages Cold Period dunes are high parabolic dunes, whereas the Little Ice Age dunes are predominantly barchanoid. The impact of trampling of the dunes by cattle during the latter period, resulting in reduced vegetation cover, and their artificial stabilization by pine forests seems to be the plausible causes of this morphological difference. Overall, the Aquitaine aeolian system is a good example of a mid-latitude coastal to inland system that was intermittently active during the Quaternary, and where the reconfiguration of the coast following sea level fluctuations played an important role in the chronological distribution of sediments.