Luis Miguel Cáceres Puro

Cambios morfológicos y tasas recientes de erosión-depósito en la costa atlántica oriental de Huelva (España)

Following the maximum Flandrian Transgression (6,900 yr. B.P.), the original coastline, with wide promontories and estuaries, underwent considerable straightening out. This was due mainly to the intense littoral dynamics, causing retreat of the capes and progradation in the inlets. Measurement of recent rates of coastal advance-retreat have been possible thanks to the number of XVIth-XVIIth century watchtowers situated on the shoreline, and to geomorphological mapping and radiometric dating of the littoral sedimentary formations (Donana). An area of maximum retreat has been identified (at the Asperillo tower) averaging around 1.2 m/yr in the last 240 years, and an area of maximum progradation (Donana) averaging up to 2-4 m/yr for the last 1,800 years and 1.05 m/year in the last 200 years. The natural evolution of this coastal stretch shows a tendency for the erosive-sedimentary point of inflexion to move eastwards, as shown by the different erosive and sedimentary landforms of the area.Fluvial landforms occupies a considerable area of the study zone. Up to now, these deposits have been interpreted as an extensive piedmont glacis. However, detailed geomorphological mapping has distinguished up to six levels of terraces, with NE-SW orientation. These levels have been correlated with those previously studied in other zones of the Guadalquivir valley, using altitudinal, sedimentological and edaphic criteria. An approximate chronology has been established, ranging from the end of the Lower Pleistocene to the beginning of the Upper Pleistocene. It reveals a gradual pushing of the terraces SE-wards on the Neogenic materials of the basin. The most recent levels are sited below the Guadalquivir marshland, with an area of maximum subsidence on a NE-SW axis, coincident with that of the Betic olisthostromic edge in this zone.