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The seabed morphology, type of sediments, and dominant benthic species on eleven mud volcanoes and diapirs located on the northern sector of the Gulf of Cádiz continental slope have been studied. The morphological characteristics were grouped as: (i) fluid-escape-related features, (ii) bottom current features, (iii) mass movement features, (iv) tectonic features and (v) biogenic-related features. The dominant benthic species associated with fluid escape, hard substrates or soft bottoms, have also been mapped. A bottom current velocity analysis allowed, the morphological features to be correlated with the benthic habitats and the different sedimentary and oceanographic characteristics. The major factors controlling these features and the benthic habitats are mud flows and fluid-escape-related processes, as well as the interaction of deep water masses with the seafloor topography. Mud volcano eruptions give rise to mud flows and/or aqueous fluid seepage. These processes sustain chemosynthesis-based communities, closely associated with fluid seepage. Large depressions in the nearby area are influenced by collapse-related phenomena, where active fluid escape and the erosive effect of bottom currents have been identified. When the extrusion activity of the mud volcano is low and the seepage is diffuse, authigenic carbonates form within the edifice sediments. The bottom current sweeps the seafloor from the SE to the NW. When the velocity is moderate, sedimentary contourite processes take place on both sides of the edifices. At high velocities, the authigenic carbonates may be exhumed and colonised by species associated with hard substrates. Small carbonate mounds are found at the summits of some volcanoes and diapirs. Living corals have been found on the tops of the shallowest mud volcanoes, revealing different oceanographic conditions and strong bottom currents that favour the availability of nutrients and organic particles. The edifices affected by very high current velocities are located in the channels where erosive processes dominate. [ABSTRACT FROM AUTHOR]

The Gulf of Cádiz (GoC) represents an area of ecological importance within the northeastern Atlantic Ocean due to the presence of Mediterranean and Atlantic water masses, a heterogeneous seafloor and a biological confluence. Nevertheless, information on the presence of vulnerable deep-sea habitats is still very scarce and it is of importance for further habitat monitoring within the context of the Habitats and Marine Strategy Framework Directives and for improving conservation and resource extraction management. From 2010 to 2012, fluid migration and emission related edifices (e.g., mud volcanoes, diapirs) from the Spanish continental margin of the GoC have been explored using a remotely operated vehicle (ROV; Liropus 2000) and an underwater camera sled (UCS; APHIA 2012) as well as several devices for collecting sediment and fauna. Different vulnerable deepsea habitats have been observed, including anoxic bottoms with bacterial mats, sea-pen communities, sponge aggregations, antipatharian and gorgonian communities and also cold-water coral banks. Some of these habitats are included in conservation lists of the habitat directive and in international conventions (OSPAR, RAC/SPA), however some of them are located in areas of the GoC that are exposed to intense trawling. The diversity of habitats detected in the Spanish continental margin of the GoC highlights the importance of seepage related edifices as inducers of seabed and habitat heterogeneity in deep-sea areas. [ABSTRACT FROM AUTHOR]

The scientific exploration of Mallorca Channel seamounts (western Mediterranean) is improving the knowledge of the Ses Olives (SO), Ausias March (AM), and Emile Baudot (EB) seamounts for their inclusion in the Natura 2000 network. The aims are to map and characterize benthic species and habitats by means of a geological and biological multidisciplinary approach: high-resolution acoustics, sediment and rock dredges, beam trawl, bottom trawl, and underwater imagery. Among the seamounts, 15 different morphological features were differentiated, highlighting the presence of 4000 pockmarks, which are seafloor rounded depressions indicators of focused fluid flow escapes, usually gas and/or water, from beneath the seabed sediments. So far, a total of 547 species or taxa have been inventoried, with sponges, fishes, mollusks, and crustaceans the most diverse groups including new taxa and new geographical records. Up to 29 categories of benthic habitats have been found, highlighting those included in the Habitats Directive: maërl beds on the summits of AM and EB, pockmarks around the seamounts and coral reefs in their rocky escarpments as well as fields of Isidella elongata on sedimentary bathyal bottoms. Trawling is the main demersal fishery developed around SO and AM, which are targeted to deep water crustaceans: Parapenaeus longirostris, Nephrops norvegicus, and Aristeus antennatus. This study provides scientific information for the proposal of the Mallorca Channel seamounts as a Site of Community Importance and for its final declaration as a Special Area of Conservation. [ABSTRACT FROM AUTHOR]

A series of six gravity cores has been used to reconstruct the depositional history of Hatton Bank (Rockall Plateau, NE Atlantic Ocean). The cores have been studied for magnetic susceptibility (MS), geochemical composition, grain size distribution, and a semi-quantitative foraminiferal association. Two main interbedded facies have been described: (i) calcareous ooze; and (ii) lithogenous silt. The study reveals prominent peaks from the MS signal, silt, Mg/Ca, Fe/Ca, Al/Ca, and Rare Earth Elements normalised by Continental Crust (REE/CC), which are sensitive indicators for Heinrich events (H1, H2, H3, H4, and H5) and ash layers. These peaks may relate to alternations in dominance of the calcareous and lithogenic facies. The sediment displays a high percentage of carbonate in interglacial layers but is lithogenic-dominated in glacial stages. The layers with prominent lithic-rich and foraminifera-poor sediments (established as Heinrich layers) may be related to a possible palaeoclimatic effect, where freshwater discharged during iceberg melting may have reduced the formation of North Atlantic Deep Water (NADW). In the study area, the mean sedimentation rates for the last glacial as ~4.2 cm ka−1 and ~1.4 cm ka−1 for the last ~18 ka (interglacial period) have been estimated. Besides this evidence, Fe/Ca and MS peaks may reflect the presence of basalt, either introduced through ice-rafting or transported and redistributed by bottom currents in the study area. Certain indices, including MS and Fe/Ca, are proposed as good proxies for detecting Heinrich events and ash layers in the Hatton Bank sediments and, in consequence, are parameters that can be used to infer strengthened/weakened NADW formation, according to stadials/interstadials. Moreover, we suggest that the northernmost boundary of the area with evidence of Heinrich events may be situated around 57°38′ N in the Hatton–Rockall area, at least for H4, based on the variation of the Mg/Ca and Fe/Ca curves. [ABSTRACT FROM AUTHOR]

The Djibouti Ville Drift is part of a contourite depositional system located on the southern side of the Djibouti Ville Seamount in the Alboran Sea (Western Mediterranean). The sedimentary record of a core located in the drift deposits has been characterized to achieve the possible sediment sources for the Saharan dust supply and the paleocurrent variability related to Mediterranean intermediate waters for the last 133 kyr. Three end-member grain-size distributions characterize the sediment record transported by the bottom current to address the different aeolian populations, i.e., coarse EM1, silty EM2, and fine EM3. For these particles, the most likely source areas are the Saharan sedimentary basins and deserts, as well as the cratonic basins of the Sahara-Sahel Dust Corridor. The prevalence of these main source areas is shown in the core record, where a noticeable change occurs during the MIS 5 to MIS 4 transition. Some punctual sediment inputs from the seamount have been recognized during sea-level lowstand, but there is no evidence of fluvial supply in the drift deposits. The paleocurrent reconstruction allows the characterizing of the stadial and cold periods by large increases in the mean sortable silt fraction and UP10, which point to an enhanced bottom current strength related to intermediate water masses. Conversely, interglacial periods are characterized by weaker bottom current activity, which is associated with denser deep water masses. These proxies also recorded the intensified Saharan wind transport that occurred during interstadial/stadial transitions. All these results point to the importance of combining sediment source areas with major climatic oscillations and paleocurrent variability in palaeoceanographic sedimentary archives, which may help to develop future climate prediction models. [ABSTRACT FROM AUTHOR]

Tagoro, the youngest submarine volcano of the Canary Islands, erupted in 2011 South of El Hierro Island. Pre-existing sea floor and inhabiting biological communities were buried by the newly erupted material, promoting the appearance of new habitats. The present study pursues to describe the first metazoans colonizing different new habitats formed during the eruption and to create precedent on this field. Through dredge and remote operated vehicle samplings, five main habitat types have been detected based on the substrate type and burial status after the eruption. Inside the Tagoro volcanic complex (TVC), two new habitats are located in and around the summit and main craters—hydrothermal vents with bacterial mats and sulfurous-like fields mainly colonized by small hydrozoan colonies. Two other habitats are located downslope the TVC; new hard substrate and new mixed substrate, holding the highest biodiversity of the TVC, especially at the mixed bottoms with annelids (Chloeia cf. venusta), arthropods (Monodaeus couchii and Alpheus sp.), cnidarians (Sertularella cf. tenella), and molluscs (Neopycnodonte cochlear) as the first colonizers. An impact evaluation was done comparing the communities of those habitats with the complex and well-established community described at the stable hard substrate outside the TVC, which is constituted of highly abundant hydrozoans (Aglaophenia sp.), antipatharians (Stichopates setacea and Antipathes furcata), and colonizing epibionts (e.g., Neopycnodonte cochlear). Three years after the eruption, species numbers at Tagoro were still low compared to those occurring at similar depths outside the TVC. The first dominant species at the TVC included a large proportion of common suspension feeders of the circalittoral and bathyal hard bottoms of the area, which could have exploited the uncolonized hard bottoms and the post eruptive fertilization of water masses. [ABSTRACT FROM AUTHOR]

The shallowest sediment of three mud volcanoes (MVs) located in the middle slope of the Gulf of Cádiz, Anastasya, Pipoca and St. Petersburg, have been seasonally studied during June and December 2016. These structures are locally important contributors of many biogeochemical active substances to the water column, with a special attention in the emission of methane (CH4). Along this study, the role of organic matter diagenesis and its contribution to the diffusive fluxes estimated in the sediment–water interface from the three MVs have been investigated mainly. For this, the first combined analyses of sediment properties (granulometry, porosity, density, organic carbon) and pore water chemistry (major elements, dissolved inorganic carbon (DIC), nutrients, CH4 and nitrous oxide) have been carried out. Anastasya and St. Petersburg MVs presented similar behaviours, with a slight concentration variation for the chemical variables in the top layers of the sedimentary record followed by a more intense vertical variation in deeper layers. Anastasya MV showed some typical processes of these structures, such as the clay dehydration, the dissolution of halite and the precipitation of authigenic carbonates, which was also observed in St. Petersburg MV. Organic matter diagenesis clearly altered the biogeochemical profiles, except for Pipoca MV. Moreover, mud breccia with a mousse-like texture has been identified in the deepest levels of Anastasya and St. Petersburg MVs. Here, anaerobic oxidation of methane is linked to the decrease of SO 4 2 - and the increases of CH4 and DIC with the core depth. Changes across the sediment–water interface presented low diffusive fluxes in the three MVs due to the presence of other processes as the irrigation by benthic macrofauna, the action of bottom currents and/or the upward fluid migration. From the obtained results, we can conclude that Anastasya MV presents a certain venting activity at present. [ABSTRACT FROM AUTHOR]

The sedimentary instability dynamics occurring over time throughout the isolated Galicia Bank (Atlantic Ocean, NW Iberian Peninsula) have been studied using a sedimentological and geotechnical approach featuring a quantitative assessment of slope stability under different scenarios, including earthquake activity. The erosion of the scarps in the Galicia Bank includes the continuous development of small instabilities evacuated along gullies and channels or deposited on slopes. These deposits may be subsequently mobilized, evolving into new sedimentary gravity flows (e.g., turbidity flow). The studied sediments consist mostly of poorly to very poorly sorted sands and silts transported by turbidity currents and occasionally by debris flow processes. The sediments in the study area identified as normally consolidated and located on gently sloping areas (gradients less than 5°) may become unstable if low-magnitude seismic events occur (PGA < 0.12). Even under static conditions, they could become unstable if they are located on slopes of > 10° without any trigger other than oversteepening. In contrast, overconsolidated sediments may remain stable under static conditions and may become unstable on slope gradients > 10° when earthquakes occur with the maximum peak ground acceleration (PGA = 0.34). The sedimentological and geotechnical models presented herein are complementary approaches that can be utilized to understand the long-term sedimentary instability dynamics observed within the study area. Such results are critical for better understanding sedimentary models of the dismantling processes of deep seamounts located far away from continental sedimentary inputs. [ABSTRACT FROM AUTHOR]

Several water masses are involved in the circulation of oceans, their bottom layers impacting on sedimentation through contourites. The majority of palaeoceanographic studies on regional contourites are performed for one water mass despite that their joint study would offer relevant clues to understand past ocean and climate interaction. This works presents for the first time a an analysis about the impact of the Light Intermediate Mediterranean (LMW) and Dense Deep Mediterranean (DMW) bottom currents on the sedimentation in the Alboran Sea (SW Mediterranean) and its paleoceanographic significance in response to climatic oscillations from the last glacial period to the Holocene. To do this, an integration of chronostratigraphical, sedimentological, and compositional data is carried out from contourites formed by those water masses. That integration enable us to define three distinct contourite stratigraphic models. (I) The contourite terrace model, characterized by coarse-grained contourites, which is an archive of the interplay between the high-energy Atlantic Water-LMW interface and glacioeustasy from the Younger Dryas (YD) to the Holocene. (II) The contourite drift models, which are archives of rapid ocean-climate coupled fluctuations since 29.5 kyr. They comprise coarse-grained contourites formed by a relatively fast LMW and fine-grained contourites formed by a relatively weak DMW, except for the Heinrich Stadials HS3 to HS1 and YD when coarse-grained contourites were deposited. (III) The contourite/turbidite mixed model represents another archive of DMW and glacioeustasy interplay from the end of the late Pleistocene to Holocene. That contourite stratigraphy allows us to infer for the first time the relative variability of the LMW versus DMW flow regimes, which records differences and similarities. The similarities indicate that the LMW and DMW fluctuations occur in parallel at millennial and centennial time scales. The differences refer to the overall higher velocity of LMW versus DMW; the magnitude changes in velocities that are lower for LMW and higher for DMW; the recognition of three short ventilation events (a, b, c) during HS1 and HS2 for only DMW; and the distinct LMW and DMW responses to the onset of glacial conditions and return to interglacial conditions during the HSs, YD and Holocene cold periods. The proposed contourite stratigraphic models can be applied for other areas in the Mediterranean margins to identify and correlate the LMW and DMW palaeoceanographic events throughout this sea. The findings suggest that the different water masses that make up the water column must be seriously considered to fully understand palaeoceanographic and palaeoclimatic studies based on contourites. This is because their distinct impact on sedimentation may provide new insights into their different palaeoceanographic responses to rapid climatic oscillations and their triggering mechanisms. • Stratigraphic models linked to Mediterranean bottom current variations are defined. • Contourite facies stratigraphy allows us to decode ocean-climate coupling. • 4th-order, millennial and centennial ocean-climate variations are confirmed. • LMW versus DMW palaeoflow regimes record differences and similarities. • Overall, palaeovelocity of LMW is higher than that of DMW. [ABSTRACT FROM AUTHOR]

This paper explains the current seafloor morphology and processes that affect the formation and evolution of three mud volcanoes and one mud volcano/mud diapir complex in the deepest sector of the Spanish margin of the Gulf of Cádiz. The present study provides novel results and interpretations based on an extensive multidisciplinary data set. New high resolution bathymetric and backscatter data from multibeam echosounders enabled a detailed geomorphological analysis aimed at identifying diverse seafloor features in the different edifices studied and their adjacent bottoms. These features are mainly related to fluid escape (e.g., mud volcanoes, mud flows and depressions), gravitational (e.g., slide deposits and scars), and tectonic (e.g., faults and uplifted antiforms) processes. Very high-resolution parametric profiles and single channel seismic reflection profiles were interpreted for further analysis of the internal structures, demonstrating their important interplay with diapiric processes. Box-corer and gravity-corer have been used to identify different sediment types that have been correlated with backscatter values. The dominant benthic species associated with fluid venting and also with different types of substrates (hard and soft) were characterized using submarine images obtained with an underwater camera deep-towed sled. The benthic species observed were contrasted, and added to those collected with beam trawl and box-corer for characterisation of the benthic and demersal communities. Different geological and biological indicators have been used as proxies of the interaction of these features with the geological processes (such as fluid-escape-related, gravitational, or structural) to characterise the environmental conditions that determine the geomorphology, substrates, habitats and their associated biota. Multivariate analyses combining faunistic and environmental data resulted in the presence of 3 main faunistic assemblages linked to different levels of fluid venting and the importance of depth and variables linked to fluid venting processes (e.g. mud breccia, Methane-derived authigenic carbonates) in the distribution of these assemblages. A conceptual model has been proposed to explain the actual seafloor morphology and the different processes that affect the formation and evolution of the fluid venting submarine structures studied. • New high resolution bathymetric model of fluid venting structures. • Proposal of geo-bio proxies to assess the fluid flow activity in seepages areas. • Proposed conceptual model for fluid venting structures. • This work draws attention to the importance of multidisciplinary studies. [ABSTRACT FROM AUTHOR]

The margin of the continental slope of the Volcanic Province of Canary Islands is characterised by seamounts, submarine hills and large landslides. The seabed morphology including detailed morphology of the seamounts and hills was analysed using multibeam bathymetry and backscatter data, and very high resolution seismic profiles. Some of the elevation data are reported here for the first time. The shape and distribution of characteristics features such as volcanic cones, ridges, slides scars, gullies and channels indicate evolutionary differences. Special attention was paid to recent geological processes that influenced the seamounts. We defined various morpho-sedimentary units, which are mainly due to massive slope instability that disrupt the pelagic sedimentary cover. We also studied other processes such as the role of deep bottom currents in determining sediment distribution. The sediments are interpreted as the result of a complex mixture of material derived from a) slope failures on seamounts and submarine hills; and b) slides and slumps on the continental slope. [ABSTRACT FROM AUTHOR]

We present a multidisciplinary study of morphology, stratigraphy, sedimentology, tectonic structure, and physical oceanography to report that the complex geomorphology of the Palomares continental margin and adjacent Algerian abyssal plain (i.e., Gulf of Vera, Western Mediterranean), is the result of the sedimentary response to the Aguilas Arc continental tectonic indentation in the Eurasian–Africa plate collision. The indentation is imprinted on the basement of the margin with elongated metamorphic antiforms that are pierced by igneous bodies, and synforms that accommodate the deformation and create a complex physiography. The basement is partially covered by Upper Miocene deposits sealed by the regional Messinian Erosive Surface characterized by palaeocanyons that carve the modern margin. These deposits and outcropping basement highs are then covered and shaped by Plio-Quaternary contourites formed under the action of the Light Intermediate and Dense Deep Mediterranean bottom currents. Even though bottom currents are responsible for the primary sedimentation that shapes the margin, 97% of this region's seafloor is affected by mass-movements that modified contourite sediments by eroding, deforming, faulting, sliding, and depositing sediments. Mass-movement processes have resulted in the formation of recurrent mass-flow deposits, an enlargement of the submarine canyons and gully incisions, and basin-scale gravitational slides spreading above the Messinian Salinity Crisis salt layer. The Polopo, Aguilas and Gata slides are characterized by an extensional upslope domain that shapes the continental margin, and by a downslope contractional domain that shapes the abyssal plain with diapirs piercing (hemi)pelagites/sheet-like turbidites creating a seafloor dotted by numerous crests. The mass movements were mostly triggered by the interplay of the continental tectonic indentation of the Aguilas Arc with sedimentological factors over time. The indentation, which involves the progressively southeastward tectonic tilting of the whole land-sea region, likely generated a quasi-continuous oversteepening of the entire margin, thus reducing the stability of the contourites. In addition, tectonic tilting and subsidence of the abyssal plain favoured the flow of the underlying Messinian Salinity Crisis salt layer, contributing to the gravitational instability of the overlying sediments over large areas of the margin and abyssal plain. • Basement, Messinian canyons, contourites and mass movements dictate geomorphology. • Mediterranean bottom currents responsible for primary Plio-Quaternary sedimentation • Large-scale gravity-driven slides above Messinian salt deposits are characterized. • Tectonic tilting of the land-sea region triggers recurrent mass movements. • A model of offshore geomorphic responses to inland tectonic indentation is presented. [ABSTRACT FROM AUTHOR]

Gazul is the shallowest mud volcano (MV) within the Shallow Field of Fluid Expulsion (SFFE) of the northeastern Gulf of Cádiz (NE Atlantic; 300–1200 m depth). The SFFE represents an important geo- and biodiversity area that was designated as a Site of Community Importance under the European Habitats Directive in 2014. In this study, geological features, habitats and associated biodiversity, as well as anthropogenic impacts, were characterized at Gazul MV from underwater imagery and multibeam bathymetry. Multivariate methods using the Bray-Curtis similarity index identified six main habitats, each of which harbored a characteristic faunal assemblage that included: (1) sandy ripple bottoms typified by the actiniarian Actinauge richardi ; (2) sandy, muddy, coarse sand and bioclastic bottoms dominated by the solitary coral Flabellum chunii ; (3) coarse sand and bioclastic bottoms, together with soft sediments covered by scattered methane-derived authigenic carbonates (MDACs) (mixed bottoms), characterized by the echinoid Cidaris cidaris ; (4) hard bottoms comprising MDACs dominated by a wide variety of sponges and gorgonians; (5) coral-rubble bottoms typified by the presence of colonial scleractinian communities dominated by Madrepora oculata ; and (6) mixed bottoms characterized by the presence of a styelid ascidian. Slope and water depth were the main factors explaining assemblages' distribution, which was also supported by the presence of MDACs such as slabs, crusts and chimneys on the seafloor, as well as by the geomorphologic diversity of Gazul MV. The results highlight Gazul MV as an eco-biologically important area harboring different vulnerable marine ecosystem (VME) elements with indicator taxa such as scleractinians, sponges, gorgonians and black corals. ROV images revealed abandoned or lost fishing gears and marine debris on the seafloor, indicating anthropogenic impacts in Gazul MV and adjacent areas. Indeed trawling fisheries activities have also been detected in Vessel Monitoring System datasets. A fishery restricted area is recommended in Gazul MV due to the occurrence of diverse VMEs and species included in different conservation directives and conventions. • Gazul MV presents a high geomorphological variability and diversity of bottom types. • Six main epibenthic assemblages have been identified conforming habitats. • Hard bottoms of the MV edifice contain the most biodiverse assemblages. • Cold-water coral communities are dominated by Madrepora oculata. • Gazul MV harbors different vulnerable marine ecosystem elements and indicators. [ABSTRACT FROM AUTHOR]

The Gulf of Cádiz represents an area of extensive seepage of the south-western Iberian Peninsula that is located between two continents and basins, where a high geomorphologic, sedimentary and environmental complexity occurs. In the present study, epibenthic communities were investigated in a mud volcano field containing four mud volcanoes (Gazul, Anastasya, Pipoca and Tarsis), one diapir/mud volcano complex (Chica) and several diapirs that are all located in the upper and middle slope of the Spanish margin of the Gulf of Cádiz (300–700 m depth). Faunistic samples were collected in 2010 and 2011 using a beam-trawl in different sectors of the mud volcano field, including fluid venting submarine structures and their adjacent seabeds. Environmental variables from the sediment and water column as well as the commercial bottom trawling activity were also measured in the same sampled areas for studying relationships with the fauna. A total of 325 taxa were found in the samples, including sponges, molluscs, cnidarians and decapods the most diverse groups. The epibenthic communities displayed differences between sectors that were related to depth, sediment features, characteristics of the water masses and the trawling activity. Six different assemblages were found including deep-sea sponge aggregations and cold-water coral banks in Gazul, echinoid and solitary coral aggregations in Gazul, sea-pen communities that were sometimes intermixed with sponge and gorgonian aggregations in Tarsis, Chica and Pipoca, and low density sea-pen communities with components of chemosynthesis-based communities in Anastasya. Species richness was higher in Gazul, Pipoca and Chica due to the presence of complex habitats (e.g. cold-water coral banks, sponge aggregations) and low in Anastasya due to the scarce epifauna, high trawling activity and low near-bottom current speed. Typical cold seep chemosymbiotic bivalves of the Gulf of Cádiz were not detected in beam-trawl samples due to their infaunal habit. The studied mud volcano field was declared a Site of Community Importance due to the presence of habitats and species with a conservation status, but several commercial species are exploited by bottom trawling. Therefore, a sustainable management of this mud volcano field is still needed according to current EU directives for combining fisheries and habitat conservation (Habitats Directive of the European Union, Directive 1992/43/EEC; Marine Strategy Framework, Directive 2008/56/EC). • A high number of taxa was detected in the mud volcano field of the northern Gulf of Cádiz. • Six epibenthic assemblages occur in different sectors and zones with different Mediterranean Outflow Water influence. • Epibenthic communities displayed relationships with depth, sediment features, water masses characteristics and trawling. • The presence of several vulnerable habitats (e.g. cold-water coral banks), may imply trawling restrictions in some sectors. [ABSTRACT FROM AUTHOR]

The Iberian margin in the Gulf of Cádiz hosts a fluid venting area embedded into a contourite depositional drift and is a natural laboratory to study how multiple interacting processes shape the seafloor. A high-resolution morpho-sedimentary analysis, based on geophysical data, sediment samples and submarine imagery, has been carried out; the onset and evolution of the main geoforms are discussed; and the influence of geological, oceanographic and biogenic processes conditioning substrate types and benthic community distribution are evaluated. The interplay of geological (e.g., salt and shale diapirism, mud volcanism), oceanographic (e.g., water mass circulation, secondary circulation, vertical eddies, internal waves) and biogenic (e.g., methane derived authigenic carbonates formation, coral mound aggradations) processes drive the formation of a large variety of geoforms including, among others, contourite drifts, channels, diapiric ridges, mud volcanoes, pockmarks, and coral mounds. At a smaller scale, the interaction between massive and fluid extrusive, biogenic, and bottom current-related processes (both depositional and erosive) determines the distribution of substrate types and benthic communities, which have been classified as belonging to different biotopes. • A number of geoforms have been mapped and their substrates and fauna described over the Iberian margin of the Gulf of Cádiz. • The onset of the geoforms depends on the interaction of a hierarchy of geological, oceanographic, and biological processes. • Massive and fluid extrusive, biogenic, and bottom current-related processes determine the distribution of biotopes. • Variable Mediterranean Outflow Water intensity reflects substrate types, related to the benthic community that host. • Several coral mounds have been mapped for the first time in the Cádiz contourite depositional systems. • Coral mound construction could be favored by alternating phases of gas migration. [ABSTRACT FROM AUTHOR]