Holocene sedimentary dynamics on the Iberian continental shelf of the Gulf of Cلdiz (SW Spain)

The Holocene evolution of the Iberian continental shelf of the Gulf of Cádiz (SW Spain) has been elucidated from a study of the granulometric facies of surficial sediments and high-resolution seismic profiles. The relationship between different facies depends on eustatic events and oceanographic conditions associated with the North Atlantic Surficial Water (NASW) on the shelf. A Transgressive Systems Tract (TST) developed as a response to a transgression (14,000–6500 yr) and deposited a transgressive sand bed on the transgressive (or ravinement) surface. A backstepping para-sequence related to a brief stillstand period has produced an onlapping shelf-transgressive erosion surface. The change in eustatic regime from transgressive to highstand in the last 6500 years has resulted in the formation of a sedimentary wedge of a Highstand Systems Tract (HST), extending from the mouth of the Guadalquivir river towards the southeast because of NASW circulation. These prodeltaic mud deposits are prograding over the older transgressive sand. The present surficial sediment distribution has been influenced greatly, therefore, by the last eustatic rise of sea level and has been divided into three main areas: (a) the littoral area; (b) northern prodeltaic mud; and (c) a southern area of relict and palimpsest sand and muddy sand, generated in a high-energy littoral environment of the Late Pleistocene-Holocene shoreline transgression.