The Guadalquivir Estuary: Spits and Marshes

The estuary of the Guadalquivir River is the largest in the Gulf of Cadiz, covering an area of some 185,000 ha. From a geological standpoint, the estuary represents the culmination of the marine filling of the Cenozoic Guadalquivir Basin. The present-day configuration of the estuary is the result of the post-glacial transgression of the Atlantic Ocean, starting ca. 15,000 years, that developed during the latest Pleistocene-Holocene up until some 5,500 years ago, when the level of the sea stabilised. The lower Guadalquivir valley was transformed into a wide estuary as the interfluves turned into pronounced headlands. Marine and fluvial dynamics, dependent upon climate and tectonics, thus shaped the present landscape, which features extensive dune systems, marshes and spits, as well as erosion of the headlands (cliff formation).