A beach-ridge progradation complex reflecting periodical sea-level and climate variability during the Holocene (Gulf of Almeria, Western Mediterranean)

Detailed mapping based on aerial photographs at various scales, analysis of morpho-sedimentary units, and radiocarbon dating of the prograding beach-ridge complex of Campo de Dalias (Almeria) allow the differentiation of six prograding units. These are called: H-1, 7400-6000 cal BP; H-2, 5400-4200 cal BP; H-3, 4200-3000 cal BP; H-4, 2700-1900 cal BP; H-5, 19001100 cal BP; and H-6, 500 cal BP-Present. H-units are deposited during periods of high relative sea level and increased sediment input to the coast. They are bounded by large swales or erosional surfaces associated with lower sea levels and reduced input of sediment to the coast; these correspond to short periods of increased aridity inside the general and trend recorded in the Western Mediterranean since 5.4 ka. Changes in the flux of Atlantic superficial waters into the Mediterranean Sea, and relative strength of the W/SW winds account for the recorded oscillations of relative sea level. We deduce a decadal periodicity for the deposition of a beach ridge and the adjacent swale, and suggest that it is related to fluctuations of the North Atlantic Oscillation (NAO) index and to variations of solar activity. The duration of H-units shows a quasi-millennial periodicity punctuated by short (hundred years) episodes of reduced progradation or erosion representing events of increased aridity likely to be related to Bond's Holocene cold events. (C) 2002 Elsevier Science B.V. All rights reserved.