The Gulf of Cádiz ( es, Golfo de Cádiz, pt, Golfo de Cádis) is the arm of the

Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...

between Cabo de Santa Maria, the southernmost point of

mainland Portugal Continental Portugal ( pt, Portugal continental, ) or mainland Portugal comprises the bulk of the Portuguese Republic, namely that part on the Iberian Peninsula and so in Continental Europe, having approximately 95% of the total population and 9 ...

and

Cape Trafalgar Cape Trafalgar (; es, Cabo Trafalgar ) is a headland in the Province of Cádiz in the southwest of Spain. The 1805 naval Battle of Trafalgar, in which the Royal Navy commanded by Admiral Horatio Nelson decisively defeated Napoleon's combined Sp ...

at the western end of the

Strait of Gibraltar The Strait of Gibraltar ( ar, مضيق جبل طارق, Maḍīq Jabal Ṭāriq; es, Estrecho de Gibraltar, Archaic: Pillars of Hercules), also known as the Straits of Gibraltar, is a narrow strait that connects the Atlantic Ocean to the Medi ...

. Two major

river A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course without reaching another body of ...

s, the

Guadalquivir The Guadalquivir (, also , , ) is the fifth-longest river in the Iberian Peninsula and the second-longest river with its entire length in Spain. The Guadalquivir is the only major navigable river in Spain. Currently it is navigable from the Gul ...

and the

Guadiana The Guadiana River (, also , , ), or Odiana, is an international river defining a long stretch of the Portugal-Spain border, separating Extremadura and Andalusia (Spain) from Alentejo and Algarve (Portugal). The river's basin extends from the e ...

, as well as smaller rivers, like the Odiel, the Tinto, and the Guadalete, reach the

ocean The ocean (also the sea or the world ocean) is the body of salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth's water. An ocean can also refer to any of the large bodies of water into which the wor ...

here. The Gulf of Cádiz is located in the north-eastern Atlantic Ocean between 34°N and 37°15′N and 6°W to 9°45′W. It is enclosed by the southern Iberian and northern Moroccan margins, west of

Geology

The geological history of the Gulf of Cádiz is intimately related to

plate tectonic Plate tectonics (from the la, label=Late Latin, tectonicus, from the grc, τεκτονικός, lit=pertaining to building) is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of large te ...

interaction between Southern

Eurasia Eurasia (, ) is the largest continental area on Earth, comprising all of Europe and Asia. Primarily in the Northern and Eastern Hemispheres, it spans from the British Isles and the Iberian Peninsula in the west to the Japanese archipelag ...

and North Africa and is driven by two major mechanisms: *

subduction Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, ...

associated with the westward emplacement of the Gibraltar Arc and formation of the Gulf of Cádiz accretionary wedge. The current activity of the subduction is unclear, with some advocating ongoing active subduction. Others suggest that subduction is inactive and that a new plate boundary has recently formed along a series of prominent WNW–ESE trending lineaments acting as a dextral strike-slip (transform) plate boundary. * oblique lithosphere collision between

Iberia The Iberian Peninsula (), ** * Aragonese language, Aragonese and Occitan language, Occitan: ''Peninsula Iberica'' ** ** * french: Péninsule Ibérique * mwl, Península Eibérica * eu, Iberiar penintsula also known as Iberia, is a pe ...

and

Nubia Nubia () ( Nobiin: Nobīn, ) is a region along the Nile river encompassing the area between the first cataract of the Nile (just south of Aswan in southern Egypt) and the confluence of the Blue and White Niles (in Khartoum in central Sud ...

. Oblique convergence between Africa (Nubia) and Iberia (Eurasia) occurs here at about per year in a NW–SE direction. Some have suggested this may also be causing active thrusting in the Gulf of Cádiz. GulfCadiz fault map

It is now well established that the whole area is under compressive deformation and that mud volcanism and processes associated with the escape of

hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or ...

-rich fluids sustain a broad diversity of chemosynthetic assemblages. The accretionary wedge formed by subduction represents an extensive area which encompasses over forty

mud volcano A mud volcano or mud dome is a landform created by the eruption of mud or slurries, water and gases. Several geological processes may cause the formation of mud volcanoes. Mud volcanoes are not true igneous volcanoes as they do not produce ...

es (a type of

cold seep A cold seep (sometimes called a cold vent) is an area of the ocean floor where hydrogen sulfide, methane and other hydrocarbon-rich fluid seepage occurs, often in the form of a brine pool. ''Cold'' does not mean that the temperature of the see ...

), at depths ranging from (confirmed by coring), and active methane seepage has been documented on several locations.

Biota

The occurrence of chemosymbiotic biota in the extensive mud volcano fields of the Gulf of Cádiz was first reported in 2003. There were found mainly pogonophoran worms, but also gastropods and bivalves, polychaetes, crustaceans and echinoderms. There were also recorded dead corals of genera ''

Madrepora Madrepora (Spanish, "mother of pores") is a genus of stony corals, often found forming reefs or islands in tropical locations. The names Madrepore and Madreporaria were formerly applied universally to any stony coral of the family Scleractinia. ...

'' and ''

Lophelia ''Lophelia pertusa'', the only species in the genus ''Lophelia'', is a cold-water coral that grows in the deep waters throughout the North Atlantic ocean, as well as parts of the Caribbean Sea and Alboran Sea. Although ''L. pertusa'' reefs are h ...

''. The chemosymbiotic

bivalve Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class (biology), class of marine and freshwater Mollusca, molluscs that have laterally compressed bodies enclosed by a shell consisting of two hing ...

s collected from the mud volcanoes of the Gulf of Cádiz were reviewed in 2011. There were reported the following species of chemosymbiotic bivalves of

Solemyidae Solemyidae is a family of saltwater clams, marine protobranch bivalve mollusks in the order Solemyida. Biology Solemyids are remarkable in that their digestive tract is either extremely small or non-existent, and their feeding appendages are too ...

: '' Acharax gadirae'', '' Solemya elarraichensis'';

Mytilidae Mytilidae are a family of small to large marine and brackish-water bivalve molluscs in the order Mytilida. One of the genera, '' Limnoperna'', even inhabits freshwater environments. The order has only this one family which contains some 52 gener ...

: '' Bathymodiolus mauritanicus'', '' Idas'' sp.;

Lucinidae Lucinidae, common name hatchet shells, is a family of saltwater clams, marine bivalve molluscs. These bivalves are remarkable for their endosymbiosis with sulphide-oxidizing bacteria. Characteristics The members of this family have a worldwi ...

: '' Lucinoma asapheus'';

Thyasiridae Thyasiridae is a family of bivalve molluscs, including the cleft clams, in the order Lucinida. Genera and species * '' Adontorhina'' S. S. Berry, 1947 ** '' Adontorhina cyclia'' S. S. Berry, 1947 ** '' Adontorhina keegani'' Barry & McCormack, ...

: '' Thyasira vulcolutre'', '' Spinaxinus sentosus''; Vesicomyidae: '' Isorropodon perplexum'', '' Isorropodon megadesmus'', '' Callogonia cyrili'', '' Christineconcha regab'', '' Laubiericoncha chuni'' and '' Pliocardia'' sp. There is high degree of

endemism Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found els ...

within chemosymbiotic bivalve assemblages.

References

{{DEFAULTSORT:Gulf Of Cadiz Gulfs of the Atlantic Ocean Bodies of water of Portugal Gulfs of Spain Geography of Southwestern Europe

Geology

Biota

See also

References