Origen y evolución de flechas litorales recientes en la desembocadura del estuario mesomareal del río Guadiana (Huelva, SO de España)

Résumé

The Guadiana River mouth (SW Spain) shows a morphology of a mesotidal estuary dominated by waves, which morpho-sedimentary evolution is strongly controlated by both fluvial and tidal activity. The southernmost sector of the eastern margin of this estuarine system has shown a very quick morphological change during the two last centuries, which reflects the space- time evolution from the diverse depositional environments there operating. The study of these changes, allows to group into two sets of environments: 1) Inner and protected environments (channels and marshes) and 2) Outer environments associated with the coastal curved spits. The dominant lithofacies in the inner environments are silty sands with a significant degree of organic reworking, controlled by the tide in a important way. In the outer environments, the sediment is medium-coarse very well sorted sands, product of both the waves activity (beaches) and eolic rework (coastal dunes). The horizontal and vertical associations of all the referred environments are ordered into a regressive sequence. The recent history of this studied sector is proposed as a recurrent displacement of both the main channel and the spit growth, beacause the swash platforms and bars are shifted. Bars acrection produces the development of spits along the eastern margin. All these processes are the consequence of the interaction among the wave regime, the tidal currents and the fluvial dynamics.