Recent coastal evolution of the Donana National Park (SW Spain)

Since the last Holocene sea level rise, about 6900 BP, a series of depositional littoral landforms has been generated at the outlet of the Guadalquivir River, with progradation along the predominant longshore drift (towards the east). The first coastal progradation occurred between 6900 and 4500 BP. The Donana and (perhaps) La Algaida spits, both associated with the oldest and highest marshland in the Donana National Park, are assumed to have been developed at an early stage. Originally, the Guadalquivir estuary was wider and deeper than now, and its environment was mainly marine. The oldest littoral formations have been dated as ca. 4735 BP. They show erosional events, and indicate the breaking-up of earlier spit-barriers to form inlets. The marine environment became increasingly dominant, with heavy erosion of cliffs and a retreating coastline. This period was followed by another sedimentary cycle (4200-2600 BP) that surrounded the earlier eroded barriers. The size of the estuary decreased due to the increasing marsh deposits, and a fluvial environment was born. About 2600 years ago, progradation gave way to a new period of intense erosion. The resulting morphology of littoral strands and erosional surfaces permitted the return to a marine environment. The shoreline again retreated. From 2300 BP, coastal progradation has prevailed, with an erosional interruption at 1000 BP. The present-day outlet of the Guadalquivir is an estuarine delta of inactive marshland (the Donana National Park), the dominant environment is fluvial. Copyright (C) 1996 Elsevier Science Ltd