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Download Date 01/10/2021 07:01:15 Oceanic intraplate volcanic islands and seamounts in the Canary Current Large Marine Ecosystem Item Type Report Section Authors Mangas, José; Quevedo-González, Luis Á.; Déniz-González, Itahisa Publisher IOC-UNESCO Download date 01/10/2021 07:01:15 Link to Item http://hdl.handle.net/1834/9175 2.2. Oceanic intraplate volcanic islands and seamounts in the Canary Current Large Marine Ecosystem For bibliographic purposes, this article should be cited as: Mangas, J., Quevedo‐González, L. Á. and Déniz‐González, I. 2015. Oceanic intraplate volcanic islands and seamounts in the Canary Current Large Marine Ecosystem. In: Oceanographic and biological features in the Canary Current Large Marine Ecosystem. Valdés, L. and Déniz‐ González, I. (eds). IOC‐UNESCO, Paris. IOC Technical Series, No. 115, pp. 39‐51. URI: http://hdl.handle.net/1834/9175. The publication should be cited as follows: Valdés, L. and Déniz‐González, I. (eds). 2015. Oceanographic and biological features in the Canary Current Large Marine Ecosystem. IOC‐UNESCO, Paris. IOC Technical Series, No. 115: 383 pp. URI: http://hdl.handle.net/1834/9135. The report Oceanographic and biological features in the Canary Current Large Marine Ecosystem and its separate parts are available on‐line at: http://www.unesco.org/new/en/ioc/ts115. The bibliography of the entire publication is listed in alphabetical order on pages 351‐379. The bibliography cited in this particular article was extracted from the full bibliography and is listed in alphabetical order at the end of this offprint, in unnumbered pages. ABSTRACT The Canary Islands and the Cape Verde Islands Volcanic Provinces show sets of islands and seamounts related to magma‐driven processes over tens of millions of years at the Canary and Cape Verde hotspots. Continuous volcanism has been reported for the last 142 Ma on the Canaries and the last 26 Ma on the Cape Verde islands to these days. The oldest ones constitute volcanic edifices formed in tens of million years, whereas the youngest ones were formed within the last hundreds of thousand years up to a few million years. Indeed, these edifices have experienced different stages from submarine‐subaerial volcanic to submarine inactive post‐stages, which formed volcanic materials with varied compositions, sedimentary rocks and bioclast‐rich, non‐consolidated marine sediments. Islands and seamounts appear with complex or simple morphologies, dome‐shaped to irregular relieves, and total heights ranging 4000‐8000 m from the bottom to the island highest peaks, but less than 3500 m on seamounts. A set of several deep‐water ecosystems is enhanced in both flora and fauna, known as traditional fishing areas expected to become protected under preservation plans, and potential mineral resources need to be further investigated. The LIFE+ INDEMARES project has provided new geological data from three Canary seamounts. Keywords: Seamounts ∙ Volcanic islands ∙ Oceanic intraplate magmatism ∙ Canary Islands ∙ Cape Verde Islands ∙ Canary Current Large Marine Ecosystem ∙ Northwest Africa IOC TECHNICAL SERIES, No. 115, pp. 39‐51. URI: http://hdl.handle.net/1834/9175. 2015 OCEANIC INTRAPLATE VOLCANIC ISLANDS AND SEAMOUNTS IN THE CANARY CURRENT LARGE MARINE ECOSYSTEM José MANGAS1, Luis Á. QUEVEDO‐GONZÁLEZ1 and Itahisa DÉNIZ‐GONZÁLEZ2 1 Instituto de Oceanografía y Cambio Global (IOCAG), Universidad de Las Palmas de Gran Canaria. Spain 2 Intergovernmental Oceanographic Commission of UNESCO. France 2.2.1. INTRODUCTION The Canary Current Large Marine Ecosystem (CCLME) involves part of the Atlantic‐type (passive) African continental margin, a marine domain where sedimentary processes prevail in both coastal and oceanic environments. Indeed, external erosive agents and sediment‐storing conditions appear in coastal areas, continental shelves (<200 m depth) and continental slopes linked to the abyssal plains with a depth range from 1000 m to 4000 m. Besides, sedimentary processes have occurred in the last 200 Ma (Lower Jurassic), once this central part of the Atlantic Ocean began to spread out. Thus, sedimentary rock layers and non‐ consolidated sediment layers reach together a thickness of 10 km width on this area (Divins, 2003). However, several areas exhibit geological anomalies due to magmatic processes (i.e. plutonic, sub‐volcanic and volcanic) since 142 Ma ago (Lower Cretaceous), thus resulting in volcanic‐originated intraplate archipelagos of both islands and seamounts (Van den Bogaard, 2013). A north‐south sequence of such volcanic edifices, namely the archipelagos of Madeira Islands, Selvagens Islands, Canary Islands, Saharan Seamounts, Cape Verde Islands and Sierra Leone Seamounts, constitutes the Magmatic Belt of Western Africa (Fig. 1.1) (Schmincke and Sumita, 2010), placed over the continental rise and the abyssal plains at this passive margin. Nonetheless, the Canary Islands and surrounding seamounts, as well as the Cape Verde islands and nearest seamounts are just those included in the CCLME region (Fig. 1.1), alluding to the hereinafter called Canary Islands Volcanic Province (CIVP) (Fig. 2.2.1) and Cape Verde Islands Volcanic Province (CVIVP) (Fig. 2.2.2). The Canary Islands archipelago is made up of 7 major islands and several islets placed in the vicinity of 28°N latitude. It extends over 500 km W of the easternmost one, Fuerteventura island, which is located 100 km off the African coastline at Cape Juby (Western Sahara) (Fig. 1.1). Considering the CIVP region, despite including approximately 100 seamounts, the largest ones were considered solely for this work (Tab. 2.2.1) (Fig. 2.2.1). CIVP seamounts expand over 700 km from Henry seamount (40 km SE of El Hierro island) to Anika seamount (300 km SE of Madeira Island). Besides, a major group of seamounts placed SW of El Hierro island, the Saharan Seamounts (e.g. Tropic, Endeavour, Bisabuelas), together with Essaouira seamount (290 km from Porto Santo, Madeira island) are geologically related to the CIVP (Van den Bogaard, 2013), even though placed out of reach of the CCLME limits. Also, seamount‐rich Cape Verde archipelago extends over 500 km W of the easternmost island of Boa Vista, which is located 600 km away off Dakar (Senegal), comprising 10 islands and several islets too, and so, located around 16°N latitude (Fig. 2.2.2). In addition, there are three seamounts at 120 km to the north‐west of Dakar, called Kayar, Petit Kayar and Petit Medina but they are independent to the Cape Verde archipelago (Fig. 1.1). Canary Islands and Cabo Verde archipelagos are part of the Macaronesian region, together with Madeira, Selvagens and Azores; even though the latter ones are found outside the CCLME region, as indeed is also the case for Sierra Leone Seamounts (Fig. 1.1). 39 Mangas, J., Quevedo‐González, L. Á. and Déniz‐González, I. Volcanic islands and seamounts in the CCLME In geological terms, the CIVP has been object of several studies (e.g. cartography, petrology, geochemistry, geomorphology, volcano‐stratigraphy) for about two centuries (see review in Schmincke and Sumita, 2010; Carracedo, 2011), whereas the CVIVP studies began in the 20th century (Bebiano, 1932). In the 60‐70 decades, research was leaded by Portuguese (Junta do Investigaçoes do Ultramar), North American and other European teams from several universities and research centres (see review in Anguita and Hernan, 2000; Madeira et al., 2010; Dyhr and Holm, 2010; Represas et al., 2012). Likewise, German research groups (Geldmacher et al., 2001, 2005, 2011; Van den Bogaard, 2013) and Spanish teams (Ancochea and Huertas, 2003; IEO, 2013a, 2013b; Quevedo‐González et al., 2012, 2014) have also focused on geological characteristics of CIVP seamounts in the last 30 years. However, a research background of CVIVP seamounts is barely supported. On the other hand, the CCLME only includes 0.2% of the seamounts worldwide (Sea Around Us Project, 2015). Hereby, this article reviews the geological knowledge of the Canary Islands and Cape Verde Islands volcanic provinces, so including the studied morphology of 28 seamounts in the CCLME region, together with some results obtained under the project LIFE+ INDEMARES (2009‐2013), concerning the seamounts of Conception Bank, El Banquete and Amanay (Quevedo‐González et al., 2012, 2014). In general, seamounts are submarine geological features showing a twofold interest, namely, scientific and economic (Staudigel and Clague, 2010). Seamounts are placed over oceanic intraplate geo‐tectonic environments, and owe their origins to mantle‐related igneous processes. Also, biogeochemical and hydrographical processes occur on these geological edifices. A variety of deep‐water seamount‐related ecosystems show enhanced biodiversity, and thus being worth to become protected areas. Economic interests surface due to related geo‐resources (e.g. phosphorites, methane hydrates, ferromanganese crusts and nodules) (Hein et al., 2010) and bio‐resources (e.g. fisheries). In both scientific and economic terms, interdisciplinary studies of these undersea mountains open up a wide range of opportunities for new international research projects in the future. 2.2.2. GEOLOGICAL SETTING In regard to crustal characteristics, the CIVP and CVIVP are located over a thick, rigid and long‐lived oceanic lithosphere, originated from the Mid‐Atlantic Ridge and defined as a slow‐spreading ridge (2.7 cm yr‐1) (Van den Bogaard, 2013). Canary Islands and seamounts from the CIVP emerge over a part of oceanic crust enclosed by the S1 (E of Lanzarote island) and the M21 (W of El Hierro island and E of
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