Interaction of tectonic and depositional processes that control the evolution of the Iberian Gulf of Cadiz margin

Abstract

This study provides an integrated view of the growth patterns and factors that controlled the evolution of the Gulf of Cadiz continental margin based on studies of the tectonic, sedimentologic and oceanographic history of the area. Seven sedimentary regimes are identified, but there are more extensive descriptions of the late Cenozoic regimes because of the larger data base. The regimes of the Mesozoic passive margin include carbonate platforms, which become mixed calcareous-terrigenous deposits during the Late Cretaceous-early Tertiary. The Oligocene and Early Miocene terrigenous regimes developed, in contrast, over the active and transcurrent margins near the African-Iberian plate boundary. The top of the Gulf of Cadiz olistostrome, emplaced in the Late Miocene, is used as a key horizon to define the 'post-orogenic' depositional regimes. The Late Miocene progradational margin regime is characterized by a large terrigenous sediment supply to the margin and coincides with the closing of the Miocene Atlantic-Mediterranean gateways. The terrigenous drift depositional regime of the Early Pliocene resulted from the occurrence of high eustatic sea level and the characteristics of the Mediterranean outflow currents that developed after the opening of the Strait of Gibraltar. The Late Pliocene and Quaternary regimes are dominated by sequences of deposits related to cycles of high and low sea levels. Deposition of shelf-margin deltas and slope wedges correlate with regressive and low sea level regimes caused by eustasy and subsidence. During the highstand regimes of the Holocene, inner shelf prograding deltas and deep-water sediment drifts were developed under the influence of the Atlantic inflow and Mediterranean outflow currents, respectively. A modern human cultural regime began 2000 years ago with the Roman occupation of Iberia; human cultural effects on sedimentary regimes may have equalled natural factors such as climate change. Interplay of tectonic and oceanographic controls dominated the evolution of the Cadiz margin during the Cenozoic. Depositional sequences formed where the tectonic setting provided the accommodation space and the shape of the deposits has been greatly influenced by the strong unidirectional Atlantic inflow currents on the shelf and Mediterranean outflow currents on the slope. The entire cycle of the inflow and outflow deposition along the margin has been controlled first by the tectonic evolution of the Betic and Rif gateways, which become closed during the Late Miocene, and after the Messinian by the opening of the Strait of Gibraltar. Strong current development during eustatic sea level highstands of the Pliocene and Quaternary has controlled deposition because of maximum sill depths at Gibraltar for water circulation. Lowstand sea levels slowed circulation and resulted in mud drapes over the slope and regressive stratigraphic sequences over the shelf. More recently, the human industrial revolution has caused heavy metal contamination of sediment and water over the Cadiz margin. H...

Punctuated Neogene tectonics and stratigraphy of the African-Iberian plate-boundary zone: concurrent development of Betic-Rif basins (southern Spain, northern Morocco)

“…Following the extension of the 'Alboran Block' and the subsidence of its adjoining foredeep with the associated precursory olistostrome emplacement in Langhian-early Tortonian times, suddenly increased rates of tectonic subsidence in late Tortonian and late Early Pliocene time triggered the emplacement of the giant olistostrome masses of the Gibraltar Arc Allochthon (Maldonado & Nelson, 1999;Maestro et al, 2003).…”

“…After late Chattian and early Aquitanian extensional and transpressional deformation in the area of the Gulf of Cadiz along a transcurrent fault system, the late Aquitanian and Burdigalian westward motion of Alboran lead to the development of a tectonically active accretionary fore arc around the emergent Gibraltar Arc (and the closure of the North African Flysch Trough). Following the extension of the 'Alboran Block' and the subsidence of its adjoining foredeep with the associated precursory olistostrome emplacement in Langhian-early Tortonian times, suddenly increased rates of tectonic subsidence in late Tortonian and late Early Pliocene time triggered the emplacement of the giant olistostrome masses of the Gibraltar Arc Allochthon (Maldonado & Nelson, 1999;Maestro et al, 2003). …”

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

“…There are also a num ber of papers dedicated to the physiography, marine geology and sedimentation in the continental shelf of the Gulf of Cadiz and 1985;Gutiérrez-Más et 1994;Hernández-Molina et al, 1994;Somoza et al, 1997;van Geen et al, 1997;Maldonado and 1999;Nelson and Maldonado, Nelson et al, 1999;. these papers did not fully extend their observations to the coastal areas were the studied incised-valleys occur.…”

Expedition 307 summary

“…Closure of the Isthmus of Panama at ~4.6 Ma rerouted the huge warm-water mass of ENAW northward and increased deepwater advection and stratification in the Atlantic (Haug and Tiedemann, 1998). In combination, MOW resumed after the late Miocene-early Pliocene salinity crisis in the Mediterranean (Maldonado and Nelson, 1999). The oldest fossil records of Lophelia and Madrepora were reported from the Mediterranean area in the early Pliocene.…”