Submarine emissions on the seafloor: from cold sepes to hot vents

The main types of submarine geological emissions are classified as cold seeps (hydrocarbons and brines) and hot vents. These processes result in the emission of geological fluids: brine, gases (mainly hydrocarbons), sediments and rocks. Submarine emissions are associated with an intensive geological, geochemical, thermal and biological activity (Judd and Hovland, 2007), and constitute a key process in the dynamics of the global cycles of the planet Earth. These systems play a major role in the exchange of matter and energy between the Geosphere and Hydrosphere, contributing to the greenhouse gases and affecting the ocean chemistry (Dimitrov, 2002; Alt, 2003). They also control the evolution of continental margins and oceanic basins (Paull y Dillon, 2001), and can produce the formation of significant and strategic mineralizations, as well as focus the development of specific habitats (Boetius et al., 2000) and provide an insight of deeper parts of the crust.LIFE+ INDEMARES/CHICA (LIFE07/NAT/E/000732), CADHYS (P08-RNM-03581), MONTERA (CTM2009-14157-C02), VULCANO (CTM2012-36317) and SUBVENT (CGL2012-39524-C02)

Preface

Instituto Español de Oceanografí

INFORME CIENTÍFICO – TÉCNICO. Campaña MONTERA‐0412

Informe de la campaña oceanográfica del proyecto MONTERA. Resultados preliminares de la campaña.La campaña MONTERA‐0412 se ha realizado A lo largo de dos zonas de los márgenes continentales del sur de Iberia: el Golfo de Cádiz y el Mar de Alborán. Ambas zonas se caracterizan por la presencia de montes submarinos y la existencia de una intensa actividad tectónica reciente. En el Golfo de Cádiz se estudiaron el Banco de Portimao, relacionado con estructuras diapíricas, y el Banco del Guadalquivir que es un alto de basamento reactivado; por otro lado los bancos estudiados en el Mar de Alborán (Bancos de Avempace, La Herradura e Ibn Batouta junto con la propia dorsal de Alboran) son en todos los casos altos de basamento bético y/o volcánico, cuya última generación de relieve está generada, así mmismo, por la actividad de estructuras tectónicas. La adquisición de nuevos datos permitirá evaluar la tasa de elevación del Banco de Portimao, así como la generación de deslizamiento cohetáneos con dicha elevación. En la zona del Banco del Guadalquivir se tendrá un mejor control de la interferencia de la Masa de Agua Mediterránea con los rasgos morfológicos del margen continental. Por último los datos obtenidos en el Mar de Alborán han permitido analizar por primera vez algunos cuerpos sedimentarios, fundamentamentalmente abanicos profundos y deslizamientos relacionados con los montes submarinos de esta zona, en este sentido se ha caracterizado batimétrica, sísmica y sedimentológicamente un nuevo deslizamiento que hemos denominado “Deslizamiento Montera”. ResumenMONTERA‐0412 scientific cruise has been conducted along two areas of the continental margins of southern Iberia: the Gulf of Cadiz and the Alboran Sea. Both are characterized by the presence of seamounts and the existence of intense recent tectonics activity. In the Gulf of Cadiz have been studied the Portimao Bank, related to diapiric structures, and the Guadalquivir Bank which is a reactivated basement high. In the Alboran Sea, the surveyed banks (Avempace, La Herradura, Ibn Batouta and the Alboran Ridge) are betic basement blocks or volcanic peleoreliefs, but in all cases they must be reactivated by Neogene‐Quaternary tectonic activity. The acquisition of new data enable the uplifted rate asessment of the Portimao Bank and their relation to simultaneous submarine mass flow processes. In the area of the Guadalquivir Bank could be expected a better control of the Mediterranean Water Mass interaction with the morphological features of the continental margin. Finally the data obtained in the Alboran Sea have allowed first analyze some deep sedimentary bodies, basicly deelp sea fans and landslides related to main seamount, in this sense has been characterized bathymetric, seismic and sedimentologically a new mass flow deposit called "Montera Slide".A campanha oceanográfica MONTERA‐0412 foi realizada ao longo de duas áreas das margens continentais do sul da Península Ibérica: o Golfo de Cádiz e o mar de Alborán. Ambas as áreas são caracterizadas pela presença de montes submarinos e pela existência de atividade tectónica no Neogeno‐Quaternário. No Golfo de Cádiz foram estudados o Banco do Portimão e as estruturas diapíricas relacionadas, e o Banco do Guadalquivir um alto de soco paleozóico reativado, por outro lado,os bancos pesquisados no Mar de Alboran (Bancos Avempace, La Herradura, Ibn Batouta e Dorsal de Alboran) sãoem todos os casos formados por altos de soco bético e/ou vulcânico e também por atividade tectónica. A aquisição de novos dados, permitirá a avaliação da taxa de soerguimento do Banco de Portimão e a geração de deslizamento simultâneos com essa elevação. Na área do Banco Guadalquivir ter‐se‐á ummelhor controle da interferência da massa de água do Mediterrâneo com as características morfológicas da margem continental. Finalmente, os dados obtidos no mar de Alborán permitiram analisar primeiramente alguns corpos sedimentares profundos, fundamentamentalmente deslizamentos de terra relacionados com os montes submarinos nesta área, e neste sentido foi caracterizado batimétrica e sísmicamente um novo deslizamento que chamámos "Deslizamento Montera".Le Mission scientifique MONTERA‐0412 a été menée dans deux zones des marges continentales du sud de l'Ibérie: le golfe de Cadix et la mer d'Alboran. Les deux régions sont caractérisées par la présence de monts sous‐marins et l'existence d'une intense activité tectonique récente. Dans le golfe de Cadix ont été étudiés le Banque du Portimao, et les structures diapíriques connexes, et le Banque du Guadalquivir qui est un 10 bloc du zocalo réactivé, de l'autre côté des banques étudié dans la mer d'Alboran (Avempace, La Herradura, Ibn Batouta et la dorsale d’Alboran) sont dans tous les cas blocs du zocle Betico et/ou dernières reliefs volcaniques, et aussi sont généré par l'activité tectonique. L'acquisition de nouvelles données permettant d'évaluer le taux d'élévation de la Banque du Portimao et la génération de glisser cohetáneos. Dans la Banque du Guadalquivir aurez un meilleur contrôle de l'interférence de la messe de l’eau méditerranéenne avec les caractéristiques morphologiques de la marge continentale. Enfin, les données obtenues dans la mer d'Alboran ont permis analyser certains corps sédimentaires profonds, fondamentalement glissements de terrain liés au monts sous‐marins dans ce domaine, en ce sens a été caractérisé bathymétrique, sismique et les sédiment d’un nouveau glissement "Montera Slide".PROGRAMA NACIONAL DE I+D+I. CTM2009-14157-C0

Submarine Active Faults and MorphoTectonics Around the Iberian Margins: Seismic and Tsunamis Hazards

The aim of this work is to make a synthesis at regional scale focused on the geophysical characterization of submarine faults around the Iberian margin to identify active structures and analyze their development in the framework of the present plate organization. Most of these submarine faults show seabed morphological expressions mapped with high-resolution swath bathymetry data, high-resolution parametric sub-bottom profiles and multichannel seismic profiles. Present active tectonics, deformation, seismicity, and tsunami-affected coastal areas is mainly focused on south Iberia at the Eurasian and Nubia plate boundary. Submarine active faults in these areas are represented by long strike-slip fault systems and arcuate fold-thrust systems. Their development takes place in response to present NW-SE convergence between the Eurasian and Nubia plates. We propose a strain partitioning model of the plate boundary into simple and pure shear zones to explain the distribution and mechanisms of active submarine faults along the Gulf of Cádiz, Gibraltar Arc and Alborán Sea in response to the present-day shear stress orientation. Nevertheless, deformation is also focused in the NW Iberian margin. Thus, along the Galician and Portuguese margin, several submarine faults mapped as thrust fault systems with high-seismic activity along the Iberian ocean-continent transition reflect the re-activation of former structures. We suggest that submarine active faults in the NW and W Iberia are also the response to the eastwards transfer of short-offset transform faults of the Mid Atlantic Ridge into the oceanic Iberian along a weakness as the former plate boundary between the oceanic Iberia and Eurasia domains. The distribution and activity of submarine faults mapped in this work from geophysical and bathymetric data are in good agreement with geodetic data and focal mechanisms.Versión del edito

El Canal de Diego Cao y sus depresiones morfológicas (margen del Banco del Guadalquivir, Golfo de Cádiz). Implicaciones oceanográficas y sedimentológicas

The Diego Cao channel is located on the central-north middle slope of the Gulf of Cadiz. It separates the Bartolomeu Dias and Faro sheeted drift plateaus to the north of the Guadalquivir Bank margin uplift. A striking linear series of circular depressions occur parallel to the channel on the Bartolomeu Dias sheeted drift (western channel flank), while a remarkable amphitheater-shaped escarpment affects the channel eastern flank. Their morphological and high- and medium-resolution stratigraphic analysis allows inferring their origin as the result of a complex interplay between oceanographic (bottom currents), mass-wasting and tectonic processes. All features seem to have a common origin, related to an especially active tectonic phase during the Mid-Pleistocene, probably related to adjustments of the deep structural features. Since then, the action of the bottom currents and the local influence of structural processes have shaped the present-day topography. The Diego Cao channel is re-interpreted as a contourite moat associated to a complex mounded, separated drift that includes the circular depressions. They result from contourite deposition over the erosional surface originated by widespread mass-wasting events during the Mid-Pleistocene.Versión del edito

Tectonic Control on Sedimentary Dynamics in Intraplate Oceanic Settings: A Geomorphological Image of the Eastern Canary Basin and Insights on its Middle-Upper Miocene to Quaternary Volcano-Tectonic-Sedimentary Evolution

This paper integrates sedimentary, tectonic and volcanic geological processes inside a model of volcano-tectonic activity in oceanic intraplate domains related to rifted continental margins. The study case, the eastern Canary Basin (NE Atlantic), is one of the few places in the world where giant MDTs and Quaternary volcanic and hydrothermal edifices take place in intraplate domains. In this paper, we analyse how two structural systems (WNW-ESE and NNE-SSW) matching with the oceanic fabric control the location of volcanic systems, seafloor tectonic reliefs and subsequently the distribution of main sedimentary systems. Linear turbidite channels, debris flow lobes and the lateral continuity of structural and volcanic reliefs follow a WNW-ESE trend matching the tracks of the oceanic fracture zones. Furthermore, escarpments, anticline axes and volcanic ridges follow a NNE-SSW trend matching normal faults delimiting blocks of oceanic basement. The morpho-structural analysis of all the above geomorphological features shows evidence of a volcanic and tectonic activity from the middle–upper Miocene to the Lower–Middle Pleistocene spread over the whole of the eastern Canary Basin that reached the western Canary Islands. This reactivation changes the paradigm in the seamount province of Canary Islands reported inactive since Cretaceous. A tecto-sedimentary model is proposed for this period of time that can be applied in other intraplate domains of the world. A tectonic uplift in the study area with a thermal anomaly triggered volcanic and hydrothermal activity and the subsequent flank collapse and emplacement of mass transport deposits on the Western Canary Slope. Furthermore, this uplift reactivated the normal basement faults, both trending WNW-ESE and NNE-SSW, generating folds and faults that control the location of turbidite channels, escarpments, mass transport deposits and volcanic edifices.Versión del edito

Origin of morphological depressions on the Guadalquivir Bank uplifted area (Gulf of Cadiz middle slope)

We have investigated the origin of morphological depressions (circular-elliptical depressions, amphitheatre-shaped escarpments and valleys) on the Guadalquivir Bank uplifted area (Gulf of Cadiz middle slope). This work is based on swath bathymetry and high- and mid-resolution reflection seismic datasets. Depressions occur on the distal (depositional) sector of the Gulf of Cadiz Contourite Depositional System, which has been developed under the influence of the Mediterranean Outflow Water (MOW). The Guadalquivir Bank is a NE-oriented relief that was uplifted along the Neogene and Quaternary. It forms the southern limit of the Bartolomeu Dias and Faro Sheeted Drift (SD) plateaus that are separated by the NW-trending Diego Cao Contourite Channel. Circular-elliptical depressions occur on the Bartolomeu Dias SD plateau, aligned parallel to the rim of the Diego Cao Channel. Irregular, crescent-shaped depressions occur to the SE of the study area and a valley surrounds the Guadalquivir Bank. The origin of these features is interpreted as the result of the interplay between oceanographic, mass-wasting, tectonic and fluid-escape processes. Four stages define the development of these features: 1) Onset of a contourite mounded drift associated with a proto-Diego Cao moat originated by a weak MOW circulation as it interacted with the structural features of the Guadalquivir Bank during the Lower Pliocene; 2) Evolution to a more complex multi-crest drift and moat system, probably as a result of an enhanced MOW and increased deformation of the underlying structures during the Upper Pliocene-Early Quaternary; 3) Event of enhanced tectonic activity that provoked widespread mass-wasting events along middle slope sheeted drift plateaus during the Mid Pleistocene. It was recorded in a prominent erosive surface under the present-day Diego Cao channel western rim and numerous slide scars displaying amphitheatre shapes on the limits of the plateaus; 4) Final stage (Late Quaternary) when the Mediterranean Intermediate Branch started flowing towards the N-NW along the deep gateway that was opened as a result of the mass-wasting event and/or structural adjustments. The contourite system evolved, due to tectonic events, to the present-day channel and a complex separated drift that includes circular depressions. They result from the interaction between the bottom current and the irregular basal surface created by the slide scars. During this phase, crescent-shaped depressions were created, probably by the interplay between bottom currents and fluid escape processes, and the marginal valley around the Guadalquivir Bank resulted from current reworking of the irregular topography of contouritic deposits affected by slide scars

Interplay of deep-marine sedimentary processes with seafloor morphology offshore Madeira Island (Central NE-Atlantic)

The deep-water sedimentary processes and morphological features offshore Madeira Island, located in the Central-NE Atlantic have been scantly studied. The analysis of new multibeam bathymetry, echo-sounder profiles and few multichannel seismic reflection profiles allowed us to identify the main geomorphologies, geomorphic processes and their interplay. Several types of features were identified below 3800 m water depth, shaped mainly by i) the interplay between northward-flowing Antarctic Bottom Water (AABW) and turbidity currents and ii) interaction of the AABW with oceanic reliefs and the Madeira lower slope. Subordinate and localized geomorphic processes consist of tectono-magmatic, slope instability, turbidity currents and fluid migration. The distribution of the morphological features defines three regional geomorphological sectors. Sector 1 represents a deep seafloor with its abyssal hills, basement highs and seamounts inherited from Early Cretaceous seafloor spreading. Sector 2 is exclusively shaped by turbidity current flows that formed channels and associated levees. Sector 3 presents a more complex morphology dominated by widespread depositional and erosional features formed by AABW circulation, and localized mixed contourite system developed by the interplay between the AABW circulation and WNW-ESE-flowing turbidite currents. The interaction of the AABW with abyssal hills, seamounts and basement ridges leads to the formation of several types of contourites: patch drifts, double-crest mounded bodies, and elongated, mounded and separated drifts. The patch drifts formed downstream of abyssal hills defining an previously unknown field of relatively small contourites. We suggest they may be a result of localized vortexes that formed when the AABW’s flow impinges these oceanic reliefs producingthe erosional scours that bound these features. The bottom currents in the area are known to be too weak (1–2 cm s− 1) to produce the patch drifts and scours. Therefore, we suggest that these features could be relics at present, having developed when the AABW was stronger than today, as during glacial/end of glacial stages

Deep crustal structure and continent-ocean boundary along the Galicia continental margin (NW Iberia)

The Galicia continental margin is a magma-poor rifted margin with an extremely complex structure. Its formation involves several rifting episodes during the Mesozoic in the vicinity of a ridge triple junction, which produces a change in the orientation of the main structures. In addition, there is an overimposed Cenozoic partial tectonic inversion along its northern border. Although this continental margin has been widely studied since the 70’s, most studies have focused on its western part in the transition to the Iberia Abyssal Plain, and there is a significant lack of information on the north and northwestern flanks of this margin. This fact, along with its great structural complexity, has resulted in the absence of a previous comprehensive regional geodynamic model integrating all the processes observed. In the present study we integrate a large volume of new geophysical data (gravity, swath bathymetry and 2D multichannel reflection seismic). Data come from the systematic mapping of the Spanish EEZ project which provides a dense grid of gravity data and full seafloor coverage with swath bathymetry, and from the ERGAP project which provides serially-arranged 2D seismic reflection profiles across the NW Iberia margin. The combined interpretation and modelling of this new information has arisen significant constraints on the origin, the deep crustal structure and the physiographic complexity of the margin, as well as on the characterization of the along- and across-strike variation of the ocean-continent transition along NW Iberia margin. The analysis of this information leads us to propose a conceptual model for the initiation of the tectonic inversion of a magma-poor rifted margin. Finally, a framework for the geodynamic evolution of the Galicia margin has been constructed, involving three main stages: A) an early stage from the end of rifting and oceanic drift in the Bay of Biscay (Santonian); B) an intermediate stage with the beginning of tectonic inversion in the north and northwestern Iberia margin (Campanian-Paleocene) mainly concentrated along the exhumed mantle zone; and C) a final stage of compressive deformation (Eocene-Oligocene) affecting both the continental and the oceanic crust, evidenced by large dip-slip thrusting.0,000

Oblique basin inversion and strain partitioning in back-arc context: example from the Moroccan Alboran Margin (Western Mediterranean)

EUROPEAN GEOPHYSICAL UNIO