Global and regional factors controlling changes of coastlines in Southern Iberia (Spain) during the holocene

Abstract

The interaction between global (glacio-eustatic sea-level rise) and regional factors (oceanographic and tectonic) has controlled the evolution of coastline during the Holocene in Southern Iberia. At ca. 10,000 14C years BP a deceleration of relative sea-level rise took place both in the Atlantic and Mediterranean littorals, with a maximum transgression at 6450 14C years BP. In subsiding areas (present tidal flats) estuaries illustrate a clear marine influence recorded both in sediments and the fauna while in uplifting areas prograding spit-bar systems developed. Two phases of major progradation are distinguished in these systems: the first one between 6450 and 3000 14C years BP, with a sedimentary gap at ca. 4000 14C years BP; and the second one from 2750 14C years BP up to present, with an intervening gap between 1200 and 1050 14C years BP. These progradation phases develop during stillstands followed by relative sea-level fall, while the sedimentary gaps represent relative high sea level. In the Mediterranean areas, with a higher uplift rate, marine terraces almost coeval to those gaps occur. The most pronounced modifications in littoral dynamics occurred at between 3000 and 2750 14C years BP represented by changes in the direction of longshore drift and prevailing winds and in the predominance of progradation over aggradation processes. At ca. 1000 14C years BP the estuaries record a greater fluvial than marine influence, and at 500 years ago an extraordinary increase in coastal progradation took place in all littoral zones. The European Medieval Warm period is characterized, at least during its initial phase, by low pressure climate conditions, while during the Little Ice Age anticyclonic conditions gave rise to a strong coastal progradation.