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 Southem 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.

The coastal archives of the last 15ka in the Atlantic–Mediterranean Spanish linkage area: Sea level and climate changes

“…1). The best, more continuous results were obtained in Guadalete (Goy et al , 1996;Dabrio et al, 1999Dabrio et al, , 2000 and OdielTinto estuaries. In the Guadalquivir estuary, the biggest of all, results are still fragmentary (Zazo et al, 1999c), and reconstructions of the fossil infill of the paleo-valley are most difficult at present owing to the lack of dated cores and complex tectonic activity.…”

“…These phases are also noted in the rates of sedimentation measured in estuaries, where the processes of vertical aggradation gave way to those of progradation, particularly since 2400 cal a BP. More open marine conditions occurred at '"'-'8000 cal a BP (Goy et al, 1996). Consequently, the coastal archives do not record the stillstands or sea level fa lIs during the cool Younger Dryas episode and Holocene Bond event at '"'-'8.2 cal ka BP seemingly recognisable in the shelf.…”

“…1). Much information comes from coastal sectors studied in previous papers (e.g., Zazo et al, 1994Zazo et al, , 1999aZazo et al, c, 2005Borja et al, 1999;Dabrio et al, 1999Dabrio et al, , 2000Goy et al, 1996Goy et al, , 2003Lario et al , 2000Lario et al , , 2002Luque, 2002;YIl et al, 2003), and from Doñana-Huelva (Rodrí-guez-Ramírez et al, 1996Ruiz et al, 2005;Cáceres et al, 2006). The paper also ineludes data from Portuguese (Bard et al, 2000); M39-008 (Cacho et al, 2001; MD95-2043 (Cacho et al, 1999(Cacho et al, , 2001Sánchez-Goñi et al, 2002);H-658 C (de Menocal et al, 2000).…”

“…Later, radiocarbon ages obtained in other prograding systems of the area (Lario et al, 1995;Goy et al , 1996;Rodriguez-Ramirez et al, 1996;Dabrio et al, 1999) were tuned with archaeological and historical data , and synchronised with the evolution history of estuarine fills .…”

Depositional history of estuarine infill during the last postglacial transgression (Gulf of Cadiz, Southern Spain)

“…A major advance has been the recognition and refinement of a chronology of events of and erosion of beaches after the maximum in the area 6500 14C years BP, Zazo et al, 1994a). In the best developed case (Goy et al, 1996, found in the Atlantic-Mediterranean area (Roquetas, SE Westem each barrier system includes four morpho-sedimentary units named spit barrier units Hl to H 4 . Discrete sets of beach crests and swales on the surface of each unit are separated by erosional surfaces andj or particularly swales called gaps.…”