Active and Passive Acoustic Methods for In-situ Monitoring of the Ocean Status

Recent European strategic plans for the successful monitoring of the status of the ocean push on the development of an integrated observing system able to further link existing instruments and techniques with the aim to complement each other and answer open issues. A more intensive use of acoustic devices could contribute to the knowledge of oceanographic processes exploiting the characteristic of sound to travel in the ocean for a wide area than in the atmosphere. In this context, the installation of passive acoustic instruments, able to listen to ambient noise on fixed or mobile platforms, could contribute to provide information on sound budget and to enhance the monitoring capacity of meteorological phenomena also in the open ocean. Instead, the deployment of active acoustic instruments can be of benefit for monitoring biological activities through the analysis of backscatter data as well as for monitoring ocean waves

The Marine Environment: Hazards, Resources and the Application of Geoethics Principles

Oceans cover three quarters of the Earth surface and represent a fundamental component of the global climate system. Life on Earth is closely tied to the climate system and thus to the oceans. Marine regions are subjected to numerous submarine natural hazards such as earthquakes, volcanic eruptions and landslides, in many cases producing tsunamis that threaten coastal areas and many onshore and offshore man-made facilities. On the other hand, as society and technological needs progressively increase, the impact of human activities on coastal and deep waters become more severe, with consequences that include global warming and sea-level rise, coastal erosion, pollution, ocean acidification, damage to marine resources and ecosystem degradation. Nevertheless, humankind seems not to be adequately conscious about the different kind of hazards threatening the marine environment. The challenge for marine geoscientists is to be conscious of the geoethical compromise in order to alert society, industries and policy makers about the needs to minimize the risks of natural and human impacts in the ocean system.Fil: Violante, Roberto Antonio. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval. Departamento Oceanografía; ArgentinaFil: Bozzano, Graziella. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval. Departamento Oceanografía; ArgentinaFil: Rovere, Elizabeth Ivonne. Secretaría de Industria y Minería. Servicio Geológico Minero Argentino; Argentin

The anomalous warming of summer 2003 in the surface layer of the Central Ligurian Sea (Western Mediterranean)

"Meteorological and sea temperature data from the ODAS Italia 1 buoy (Ligurian Sea, Western Mediterranean) are used to study the anomalous warming of summer 2003 at sea. The event was related to the record heat wave that interested much of Europe from June to September of that year. The data show that the anomalous warming was prevalently confined to within a few meters below the sea surface. On the contrary, the temperatures in the underlying layers were lower than usual. The limited vertical propagation of heat is ascribed to the high temperature difference that arose between the surface and the deeper layers due to protracted calm weather conditions. The degree of penetration of heat deduced from the observations is consistent with that computed on the basis of an energetic argument, wherein the wind constitutes the sole supply of kinetic energy, while the heating is viewed as the source of potential energy that must be ""subtracted"" by mixing. The results support the hypothesis that the scanty energy from the wind is mainly responsible for the development of the temperature anomaly at the sea surface.

Comparison of ECMWF surface meteorology and buoy observations in the Ligurian Sea

Since numerical weather prediction (NWP) models are usually used to force ocean circulation models, it is important to investigate their skill in reproducing surface meteorological parameters in open sea conditions. Near-surface meteorological data (air temperature, relative humidity, barometric pressure, wind speed and direction) have been acquired from several sensors deployed on an offshore large spar buoy in the Ligurian Sea (Northern Mediterranean Sea) from February to December 2000. The buoy collected 7857 valid records out of 8040 during 335 days at sea. These observations have been compared with data from NWP models and specifically, the outputs of the ECMWF analysis in the two grid points closest to the buoy position. Hourly data acquired by the buoy have been undersampled to fit the data set of the model composed by values computed at the four synoptic hours. For each mentioned meteorological parameter an analysis has been performed by evaluating instantaneous synoptic differences, distributions, daily and annual variations and related statistics. The comparison shows that the model reproduces correctly the baric field while significant differences result for the other variables, which are more affected by local conditions. This suggests that the observed discrepancies may be due to the poor resolution of the model that probably is not sufficient to appropriately discriminate between land and ocean surfaces in a small basin such as the Ligurian Sea and to take into account local peculiarities. The use of time- and space-averaged model data reduces the differences with respect to the in situ observations, thus making the model data usable for analysis with minor requirements about time and space resolution. Although this comparison is strongly limited and we cannot exclude measurement errors, its results suggest a great caution in the use of the model data, especially at high frequency resolution. They may lead to incorrect estimates of atmospheric forcing into ocean circulation models, causing important errors in those areas, such as the Mediterranean Sea, where ocean circulation is strongly coupled with atmosphere and its high variability

The submarine canyons of the Argentine Continental Margin: a review of their formation and sedimentary dynamics

Los cañones submarinos son los mayores rasgos erosivos de los márgenes continentales tanto activos como pasivos. Desde los albores del siglo XX, representan un fructífero tema de debate e investigación por su gran relevancia como agentes de transferencia de sedimento y materia orgánica de continente a océano, por ser lugar de surgencia de aguas profundas, elevada producción primaria y riqueza en biodiversidad, y por ser potenciales factores de riesgo en las rupturas de infraestructuras submarinas. El presente trabajo comprende una revisión de las principales teorías de formación y evolución de los cañones submarinos así como de los procesos de interacción entre dinámica oceanográfica, flujos sedimentarios y morfologías asociadas a los cañones. El objetivo es presentar una síntesis del estado del conocimiento sobre los cañones del Margen Continental Argentino (MCA), discutir su formación y evolución en el marco de los modelos genéticos más aceptados en la actualidad así como proponer una hipótesis de trabajo vinculada a la dinámica sedimentaria del Cañón Mar del Plata (MdP), el más estudiado del margen. Este cañón, como la mayoría de los del MCA, por un lado se desarrolla exclusivamente en el talud (cañón ciego) y por el otro interrumpe un gran sistema depositacional contornítico relacionado con la circulación oceanográfica regional. De aquí que su génesis en principio se explicaría por el modelo de erosión retrogradante a partir de fenómenos de inestabilidad del talud, pero además podría funcionar como trampa de sedimento captando el material transportado por el Agua Antártica Intermedia a lo largo del talud medio. Se propone que en la Terraza Ewing, donde el cañón tiene su cabecera, podrían generarse corrientes turbidíticas que afectarían a la evolución y dinámica del cañón. Estas corrientes se encauzarían cañón abajo contribuyendo a profundizar su valle y a conformar su trazado en parte sinuoso. En los sistemas de cañones Patagonia otros factores podrían activar la génesis de los cañones submarinos. Se ha sugerido la posibilidad que irregularidades morfológicas provocadas por la acción erosiva de las corrientes contorníticas sobre el fondo puedan dar origen a los cañones de esta zona. Este mecanismo podría no limitarse exclusivamente al sistema Patagonia sino aplicarse a los demás sistemas de cañones argentinos ya que el MCA está intersectado por intensas corrientes de contorno que operan a diferentes profundidades.Submarine canyons are the most outstanding geomorphologic features of continental margins. They play a fundamental role in transferring sediment and organic matter from shallow to deep waters. Also, they influence oceanographic and sedimentary processes, interact with productivity and benthic ecosystems, and pose a serious threat to seafloor infrastructures. Submarine canyons have been described as steep-walled, sinuous valleys with V-shaped cross sections, axes sloping outward as continuously as river-cut land canyons and relief comparable to even the largest of land canyons. The understanding of the origin and evolution of submarine canyons has been matter of intense debate since the first geologists observed them characterizing both passive and active margins. Canyons have been interpreted as (1) the off-shore prolongation of river systems that during low sealevel stages migrated seaward; (2) the product of the erosion caused by gravity dense flows- called turbidity currents- produced at the shelf-slope transition; (3) the deepening of pre-existing tectonic structures (e.g. faults) and (4) the result of slope instability combined with headward erosion. The first model only explains the genesis of the breaching-shelf canyons that connect with river systems, but does not resolve the formation of those that are unrelated to fluvial input. Turbidity currents take place at the shelf break when sufficient amount of sediment is injected into the water column by (re) suspension, resulting in a flow with higher density than the surrounding waters. These high-density flows, moving down-slope under the effect of gravity, cut the valleys that finally evolve into submarine canyons. Turbidity currents, though effective agents of erosion, do not account for the formation of slopeconfined canyons. From the other side, tectonic control can apply for limited examples of canyons, which are located in specific geological contexts. Continental slopes often show scars that are left behind by instability events. Mass wasting processes may arise from fluid escape, sediment over pressure and steepening or be triggered by seismic shocks. These initial scars would evolve into rills and then into valleys by a process that combines localized slope failures, sediment funneling and headward erosion. According to this genetic model, slope-confined and shelf-breaching canyons are, respectively, the early and mature stages in the evolution of canyons, which starts with a pre-canyon rill that advances upslope by retrogressive failure and ends with the canyon cutting the shelf break. The objective of this contribution is to review the knowledge on the submarine canyons from the Argentine Continental Margin and to suggest a working hypothesis concerning the sedimentary dynamics of the Mar del Plata Canyon, by far the best known canyon of this margin. Four main systems have been described: La Plata River, Colorado-Negro (or Bahía Blanca), Ameghino (or Chubut) and Patagonia (or Deseado). Mar del Plata Canyon, belonging to the first of these systems, cuts the slope between ~1000 m (Ewing Terrace, middle slope) and ~3900 m (lower slope-continental rise transition) as a deep valley with steep walls. In its proximal sector, between 1100 and 3000 m, it shows a sinuous path whereas the thalweg is mostly linear between 3000 an 3900 m. Seismic profiles, obtained during the Meteor research cruise M78/3a, demonstrate no evidences of incisions that could suggest past fluvial connections with the canyon head. For this reason, the origin of this canyon has been explained as an example of headward erosion. During the Holocene, the sedimentation rate inside the canyon is much higher than outside. This occurs because the large amount of sediment mobilized by bottom currents along the Ewing Terrace is intercepted by the canyon. In contrast, during the Late Glacial and deglaciation phase, turbidite accumulation has been attributed to slope instability of the drift deposits at the southern flank of the canyon. In this study, we put forward the following working hypothesis: the canyon most probably generated from slope instability and retrogressive erosion. However, when the valley moved upslope and etched the Ewing Terrace (middle slope), turbidity currents might have been produced at this water depth (1000-1200 meters) by the peculiar oceanographic dynamics driven by the interaction between bottom currents and seafloor. If confirmed by future investigations, this hypothesis would account both for the turbidite deposition and the sinuous path of the canyon in its proximal sector, which is more typical, although not exclusive, for canyons routed by turbidity currents. The detailed morphological investigations, performed in the Patagonia Canyons system by a Spanish research group in 2011, add a stimulating source of discussion about canyon formation in the Argentine Margin. These authors have proposed that topographic irregularities shaped by scars resulting from the sea-floor erosion under strong contour currents and the step separating terraces located at different water depths, might be the precursors for a pre-canyon incision. This hypothesis, of great relevance in a continental margin where downslope and along-slope sedimentary processes often coexist and interact, probably apply not only to the Patagonia but also to the other, less investigated, canyons systems of the Argentine Margin.Fil: Bozzano, Graziella. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Martín de Nascimento, Jacobo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Spoltore, Daniela V.. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval; ArgentinaFil: Violante, Roberto Antonio. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval; Argentin

Engineering-geological modeling for supporting local seismic response studies. Insights from the 3D model of the subsoil of Rieti (Italy)

A high-resolution 3D engineering-geological model of the subsoil can be derived by integrating stratigraphic and geophysical data in order to represent reliably the geological setting, and therefore support several geological studies such as local seismic response analyses. In this study, we show how an accurate 3D engineering-geological model suggests the proper seismic response modeling approach (1D or 2D) in a peculiar and complex geological context, such as the historical city center of Rieti (Italy), selected as test site, and characterized by important lateral heterogeneities between stiff travertine and alluvial soft deposits. The proposed methodology involves three steps: (i) conceptual geological modelling, obtained from data and maps of literature; (ii) engineering-geological modeling, validated through geophysical data; and (iii) a 3D model restitution achieved by a geodatabase (built basing on the previous steps), that collects, stores, reliably represents, and integrates properly the geospatial data. The analysis of seismic ambient noise measurements specifically available for the study area allowed to infer the shear wave velocity value for each lithotecnical unit and to retrieve some additional stratigraphies. These synthetic log stratigraphies allowed to improve the detail of the geodatabase and therefore a more accurate 3D geological model. Such a reliable engineering-geological model of the subsoil is required to perform a site-specific seismic response characterization which is a fundamental tool in the framework of seismic risk management

Engineering-geological features supporting a seismic-driven multi-hazard scenario in the Lake Campotosto area (L’Aquila, Italy)

This paper aims to describe the seismic-driven multi-hazard scenario of the Lake Campotosto artificial basin (Abruzzo Region, Central Italy), and it can represent a preparatory study for a quantitative multi-hazard analysis. A comprehensive multi-hazard scenario considers all the effects that can occur following the base ground shaking, providing a holistic approach to assessing the real hazard potential and helping to improve management of disaster mitigation. The study area might be affected by a complex earthquake-induced chain of geologic hazards, such as the seismic shaking, the surface faulting of the Gorzano Mt. Fault, which is very close to one of the three dams that form the Lake Campotosto, and by the earthquake-triggered landslides of different sizes and typologies. These hazards were individually and qualitatively analyzed, using data from an engineering-geological survey and a geomechanical classification of the rock mass. With regard to the seismic shaking, a quantitative evaluation of the seismic response of the Poggio Cancelli valley, in the northern part of Lake Campotosto, was performed, highlighting different seismic amplification phenomena due to morphologic and stratigraphic features. Some insights about the possible multi-hazard approaches are also discussed

Los cañones submarinos del Margen Continental Argentino: una síntesis sobre su génesis y dinámica sedimentaria

Los cañones submarinos son los mayores rasgos erosivos de los márgenes continen­ tales tanto activos como pasivos. Desde los albores del siglo XX, representan un fructífero tema de debate e investigación por su gran relevancia como agentes de transferencia de sedimento y materia orgánica de continente a océano, por ser lugar de surgencia de aguas profundas, elevada producción primaria y riqueza en biodiversidad, y por ser potenciales factores de riesgo en las rupturas de infraestructuras submarinas. El presente trabajo comprende una revisión de las principales teorías de formación y evolución de los cañones submarinos así como de los procesos de interacción entre dinámica oceanográfica, flujos sedimentarios y morfologías asociadas a los cañones. El objetivo es presentar una síntesis del estado del conocimiento sobre los cañones del Margen Continental Argentino (MCA), discutir su formación y evolución en el marco de los modelos genéticos más aceptados en la actualidad así como proponer una hipótesis de trabajo vinculada a la dinámica sedimentaria del Cañón Mar del Plata (MdP), el más estudiado del margen. Este cañón, como la mayoría de los del MCA, por un lado se desarrolla exclusivamente en el talud (cañón ciego) y por el otro interrumpe un gran sistema depositacional contornítico relacionado con la circulación oceanográfica regional. De aquí que su génesis en principio se explicaría por el modelo de erosión retro­ gradante a partir de fenómenos de inestabilidad del talud, pero además podría funcionar como trampa de sedimento captando el material transportado por el Agua Antártica Intermedia a lo largo del talud medio. Se propone que en la Terraza Ewing, donde el cañón tiene su cabecera, podrían generarse corrientes turbidíticas que afectarían a la evolución y dinámica del cañón. Estas corrientes se encauzarían cañón abajo contribuyendo a profundizar su valle y a conformar su trazado en parte sinuoso. En los sistemas de cañones Patagonia otros factores podrían activar la génesis de los cañones submarinos. Se ha sugerido la posibilidad que irregularidades morfológicas provocadas por la acción erosiva de las corrientes contorníticas sobre el fondo puedan dar origen a los cañones de esta zona. Este mecanismo podría no limitarse exclusivamente al sistema Patagonia sino aplicarse a los demás sistemas de cañones argentinos ya que el MCA está intersectado por intensas corrientes de contorno que operan a diferentes profundidades

Sedimentación marina profunda en el margen continental Argentino: revisión y estado del conocimiento.

El Margen Continental Argentino (MCA) ocupa un lugar privilegiado en el océano mundial por su contexto oceanográfico altamente dinámico asociado a la circu­ lación global, que favorece el desarrollo de extensas capas nefeloides con gran cantidad de sedimentos en suspensión, así como una alta energía de los agentes de erosión y transporte que son capaces de movilizar sedimentos en el fondo marino. Estas condiciones coadyuvan a la ocurrencia de procesos sedimentarios profundos de gran magnitud y complejidad. El margen comenzó a ser estudiado a partir de mediados del siglo XX. El conocimiento que se tenía por ese entonces, que acompañaba a las hipótesis de la época a nivel internacional, señalaba que los procesos sedimentarios dominantes en las regiones profundas del talud y emersión eran los gravitacionales y pelágicos. Se desconocía la influencia de las corrientes de fondo asociadas a la estructura oceanográfica de carácter termohalina, al menos en magnitud importante como para ejercer un efecto modelador significativo sobre el suelo marino. Estudios realizados en las últimas dos décadas alertaron sobre la ocurrencia de procesos sedimentarios asociados a corrientes profundas paralelas al margen capaces de construir cuerpos contorníticos (drifts) elongados en el sentido de circulación de las corrientes. El redescubrimiento de estos procesos llevó a cambiar substancialmente los mapas del lecho marino. Estos nuevos conceptos no solamente marcaron un significativo avance en el campo de la Geología Marina, sino que permitieron comprender que ésta no podía ser considerada e interpretada sin el apoyo de la Oceanografía Física. En base a la interrelación entre los tres procesos sedimentarios básicos que ocurren en los fondos marinos (longitudinales, gravitacionales y pelágicos), el MCA es subdividido regionalmente, de norte a sur, en seis regiones, cada una con sus rasgos morfosedimentarios propios, de acuerdo fundamentalmente a las características que presentan las formas resultantes de los procesos dominantes, que son los contorníticos y gravitacionales. Regionalmente, en el sector de margen pasivo los cuerpos contorníticos son continuos a lo largo de 1600 km, denotando la gran extensión sobre la cual actúan las corrientes de fondo; su magnitud (extensión y espesores) disminuyen progresivamente de sur a norte, debido a factores múltiples como la decreciente dinámica de aquellas corrientes y la interacción con procesos gravitacionales. No obstante, vuelven a adquirir grandes dimensiones hacia el margen de Brasil en un contexto oceanográfico diferente al del margen argentino. En cambio, en los sectores de márgenes transcurrente y mixto adyacentes al sector sur patagónico y Arco de Scotia, los cuerpos contorníticos son más reducidos en tamaño (pocas centenas de km de extensión) y en general de menores espesores, dado que se vinculan a sectores localizados en fosas, canales, taludes de extensión limitada, y pasajes entre altos estructurales y elevaciones del fondo

Deep marine sedimentation in the Argentine Continental Margin: Revision and state-of-the-art

El Margen Continental Argentino (MCA) ocupa un lugar privilegiado en el océano mundial por su contexto oceanográfico altamente dinámico asociado a la circulación global, que favorece el desarrollo de extensas capas nefeloides con gran cantidad de sedimentos en suspensión, así como una alta energía de los agentes de erosión y transporte que son capaces de movilizar sedimentos en el fondo marino. Estas condiciones coadyuvan a la ocurrencia de procesos sedimentarios profundos de gran magnitud y complejidad. El margen comenzó a ser estudiado a partir de mediados del siglo XX. El conocimiento que se tenía por ese entonces, que acompañaba a las hipótesis de la época a nivel internacional, señalaba que los procesos sedimentarios dominantes en las regiones profundas del talud y emersión eran los gravitacionales y pelágicos. Se desconocía la influencia de las corrientes de fondo asociadas a la estructura oceanográfica de carácter termohalina, al menos en magnitud importante como para ejercer un efecto modelador significativo sobre el suelo marino. Estudios realizados en las últimas dos décadas alertaron sobre la ocurrencia de procesos sedimentarios asociados a corrientes profundas paralelas al margen capaces de construir cuerpos contorníticos (drifts) elongados en el sentido de circulación de las corrientes. El redescubrimiento de estos procesos llevó a cambiar substancialmente los mapas del lecho marino. Estos nuevos conceptos no solamente marcaron un significativo avance en el campo de la Geología Marina, sino que permitieron comprender que ésta no podía ser considerada e interpretada sin el apoyo de la Oceanografía Física. En base a la interrelación entre los tres procesos sedimentarios básicos que ocurren en los fondos marinos (longitudinales, gravitacionales y pelágicos), el MCA es subdividido regionalmente, de norte a sur, en seis regiones, cada una con sus rasgos morfosedimentarios propios, de acuerdo fundamentalmente a las características que presentan las formas resultantes de los procesos dominantes, que son los contorníticos y gravitacionales. Regionalmente, en el sector de margen pasivo los cuerpos contorníticos son continuos a lo largo de 1600 km, denotando la gran extensión sobre la cual actúan las corrientes de fondo; su magnitud (extensión y espesores) disminuyen progresivamente de sur a norte, debido a factores múltiples como la decreciente dinámica de aquellas corrientes y la interacción con procesos gravitacionales. No obstante, vuelven a adquirir grandes dimensiones hacia el margen de Brasil en un contexto oceanográfico diferente al del margen argentino. En cambio, en los sectores de márgenes transcurrente y mixto.Introduction The Argentine Continental Margin (ACM), one of the largest margins worldwide, shows varied geotectonic and morphosedimentary settings (Fig. 1) with a complex oceanographic configuration (Fig. 2), as a consequence of the highly energetic oceanographic framework (Hastenrath, 1982; Berger and Wefer, 1996; Wefer et al., 1996, 2004; Mata et al., 2001; Bryden and Imawaki, 2001; Talley, 2003; Carter and Cortese, 2009). These configurations produce a complex sediments dynamic resulting from two major processes: the formation of nepheloid layers with an enormous amount of suspended sediments (Ewing et al., 1971; Biscaye and Eittreim, 1977; Emery and Uchupi, 1984; Bearmon, 1989; Scholle, 1996) and the activity of very strong bottom currents with high capacity for producing energetic erosive and depositional processes affecting the sea floor. The result of these sets of conditions is responsible of the unusual high sand content of this margin in relation to others in the world (Lonardi and Ewing, 1971; Frenz et al., 2004; Bozzano et al., 2011). Although the margin has been studied since mid XX century (Heezen and Tharp, 1961, in Heezen, 1974; Ewing et al., 1964; Ewing, 1965; Ewing and Ewing, 1965; Ewing and Lonardi, 1971; Lonardi and Ewing, 1971; Le Pichon et al., 1971; Urien and Ewing, 1974; Mouzo, 1982; Emery and Uchupi, 1984; Pudsey et al., 1988; Lawver et al., 1994; Parker et al., 1996, 1997; Coren et al., 1997; King et al., 1997; Gilbert et al., 1998; Pudsey and Howe, 1998), an exhaustive analysis of the sedimentary processes involved in its evolution is a still pending issue. However, recent studies carried out since the beginning of the XXI century with the pioneering works by Pudsey and adyacentes al sector sur patagónico y Arco de Scotia, los cuerpos contorníticos son más reducidos en tamaño (pocas centenas de km de extensión) y en general de menores espesores, dado que se vinculan a sectores localizados en fosas, canales, taludes de extensión limitada, y pasajes entre altos estructurales y elevaciones del fondo. Howe (2002) and Cunningham et al. (2002) in the Scotia Sea, and Hernández Molina et al. (2009) in the passive sector of the margin, initiated the epoch of more specific investigations that led to revisit most of the concepts concerning the deep-sea sedimentation previously considered. The objective of this contribution is to synthesize the present knowledge on deep sedimentary processes in the ACM, previously discussing the change from the "turbiditic" to the "contouritic" models that took place as a result of the studies performed in the region during the last 30 years. This change followed the advance in the conception of deep-marine sedimentary processes that occurred worldwide, as expressed by Swallow and Worthington (1957), Stommel (1958), Heezen and Hollister (1964), Hollister (1967), Shanmugan (2000), Stow et al. (2002), Mc.Cave (2002), Rebesco and Camerlenghi (2008), Hsü (2008) and Rebesco et al. (2014), among others. Argentine Continental Margin (ACM): state of the art The first reference to the sedimentary processes acting in the slope and rise of the ACM was done by Ewing et al. (1964), who stressed the relevance of submarine canyons and nepheloid layers as the main ways of transport of fine sediments to the deep regions, being pelagic sedimentation of minor importance. Only in the abyssal plains those authors mentioned the possibility of bottom currents acting on the sea floor. Later contributions by Le Pichon et al. (1971), Lonardi and Ewing (1971) and Ewing and Lonardi (1971) reinforced those concepts and mentioned the bottom currents forming the drifts (contouritic bodies) in the Argentine Basin. Although some subhorizontal terraces were later described in the middle slope by Lonardi and Ewing (1971) and Ewing and Lonardi (1971), the consideration of the continental slope as a high-gradient feature mostly erosive and dominated by turbiditic processes still prevailed at those times (Heezen and Tharp, 1961, en Heezen, 1974; Emery and Uchupi, 1984) (Fig. 3), even if Wüst (1957, in Heezen 1973) had previously noticed that strong bottom currents swept the continental slope of eastern South America. Moreover, as shown for example by Ewing and Lonardi (1971) and Pudsey and Howe (2002), seafloor photographs taken in the decades of 1960-1970 in the Argentine margin (GeoMapApp, 2013) already illustrated unidirectional ripples in the slope (Fig. 4). The advance in the knowledge and application of the new models proposed at those times in the world, led to the first mention to contouritic deposits in the ACM by Pudsey et al. (1988) in the Scotia Sea and surroundings, followed by new findings in the region by Lawver et al. (1994), Coren et al. (1997), King et al. (1997), Gilbert et al. (1998), Pudsey and Howe (1998, 2002), Cunningham et al. (2002), Maldonado et al. (2003, 2006) and Koenitz et al. (2008). Later contributions by Rovira et al. (2013), Esteban (2013), Pérez (2014) and Pérez et al. (2015) improved the knowledge in those areas. In the passive margin, Hernández Molina et al. (2009) described for the first time the very extensive and complex Contourite Depositional System (CDS) developed along 1600 km. Following this, the contributions by Hernández Molina et al. (2010, 2011), Violante et al. (2010b), Bozzano et al. (2011), Gruetzner et al. (2011, 2012, 2016), Lastras et al. (2011), Muñoz et al. (2012) and Preu et al. (2012, 2013) provided more detailed information about the CDS in some localized areas of the margin. The development of the concept of contouritic sedimentation in the ACM was necessarily related to the consideration that along-slope deepmarine sedimentary processes are closely linked to the activity of bottom currents interacting with the sea-floor. Taking into account the particularly energetic ocean dynamic in the region and the strong thermohaline stratification (Reid et al. 1977; Piola and Gordon, 1989; Bianchi et al., 1993; Saunders and King 1995; Boebel et al., 1999; Arhan et al. 1999, 2002a, 2002b, 2003; Piola and Matano 2001; Bianchi and Gersonde, 2002; Henrich et al. 2003; Carter et al. 2008), and considering that this oceanographic structure evolved since Eocene-Oligocene times (Hinz et al., 1999; Zachos et al., 2001; Lawver and Gahagan, 2003; Livermore et al., 2004; Cavallotto et al., 2011; García Chapori, 2015), it is easy to understand that the sedimentary architecture and the morphosedimentary configuration of the margin strongly responded to the impact of bottom currents on the sea-floor acting along large periods of time, so shaping the continental margin (Pudsey and Howe, 2002; Cunningham et al., 2002; Hernández Molina et al., 2009, 2010, 2011; Violante et al., 2010 b; Lastras et al., 2011; Muñoz et al., 2012; Preu et al., 2012, 2013; Gruetzner et al., 2011, 2012, 2016; Pérez et al., 2015). However, the above mentioned processes varied regionally depending on the geotectonic framework of the margin, which is composed of four types of margins (Pelayo and Wiens, 1989; Ramos, 1996; Hinz et al., 1999; Mohriak et al., 2002; Franke et al. 2007, 2010; Cavallotto et al., 2011; Violante et al., 2017) (Fig. 1): passive, transcurrent, mixed and active. Consequently, and according to the entire set of factors involved in different regions of the margin (geotectonic, morphological, sedimentary, oceanographic, etc.) and their regional variations, six zones are identified from north to south (Fig. 5). Five of them correspond to the passive margin and one encompasses the transcurrent, mixed and active margins. Northeastern Buenos Aires (36-38°S). Large submarine canyons and mass-transport deposits shaping the slope, as well as an extensive rise, are the major features in this region. The largest canyons systems are Rio de la Plata and Mar del Plata, which were previously described by different authors (Lonardi and Ewing, 1971; Ewing and Lonardi, 1971; Violante et al. 2010 a; Bozzano et al., 2011; Krastel et al. 2011; Preu et al. 2012, 2013; Voigt et al. 2013, 2016). Dominant processes are gravitational, producing turbiditic and mass-transport deposits, with contouritic drifts in the terraces between canyons. Major terraces are La Plata (T1, at ~500-600 m depth), Ewing (T2, at 1200-1500 m), T3 (restricted to the northern flank of the Mar del Plata canyon at 2500 m) and Necochea (T4, at 3500 m) (Hernández Molina et al., 2009; Preu et al., 2013). Drifts are plastered and mounded in the Ewing terrace and plastered to detached in the Necochea terrace. The rise is wide as a result of the highly significant downslope processes. Contouritic drifts are 700 to 1000 m thick and are composed of gravelly, sandy-silty and muddy facies. This zone extends northwards towards the Uruguayan margin (Franco- Fraguas et al., 2014, 2016; Hernández-Molina et al., 2015). Southeastern Buenos Aires (38-40°30'S). Dominant morphological elements in the slope are contouritic terraces (the same that in the northern region), which are affected, and partially interrupted, by small submarine canyons. The rise in this region is progressively reduced in size towards the south. Several contouritic drifts (plastered) have been described (Hernández-Molina et al., 2009; Violante et al., 2010 b; 2012; Bozzano et al., 2011; Preu et al., 2012, 2013; Gruetzner et al., 2016). La Plata and Ewing contouritic terraces show their largest development here, with drift's thicknesses up to 1 km. Despite the small size of submarine canyons, they seem to play a significant role in transporting sediments offshore as evidenced by large turbiditic lobes and mass-transport deposits present at the base of the slope, although they show reoriented patterns to the northeast due to the strong activity of northward flowing deep contouritic currents, so constituting mixed features where detached drifts are recognized (Hernández Molina et al., 2009). Northern Patagonia (40°30'-42°30'S). Contouritic terraces dominate the landscape of the slope in this region, although they are highly dissected by a dense net of small submarine canyons; a narrow rise is present in this region. Contouritic drifts are plastered and mounded (Hernández Molina et al., 2010; Gruetzner et al., 2016), with thicknesses up to 1600 m and a sandy-muddy texture. However, gravitational processes are also important as evidenced by the significance of slides and mass-transport deposits in the middle slope, rise and western flank of the Argentine Basin (Hernández Molina et al., 2009; Bozzano et al., 2014; Costa et al., 2014). Central-northern Patagonia (42°30'-46°S). The most impressive features in this region are the large Submarine Canyons Systems Ameghino and Almirante Brown, which are the largest canyons in the ACM. They are transverse to the slope in their upper and middle sections, but in the mid-lower slope they run parallel to the isobaths. Although tectonic processes have been considered for explaining the change in the canyon's direction (Rosello et al., 2005), recent studies indicate the strong influence of alongslope currents able to deflect the canyons to the north (Hernández Molina et al., 2009; Lastras et al., 2011; Muñoz et al., 2012). Where contouritic drifts were recognized around the canyons, they are dominantly plastered with thickness up to 1600 m. Central-southern Patagonia (46-49°S). Very large contouritic terraces develop here, shaping four major terraces (Nágera, at ~500 m depth, Perito Moreno, at ~1000 m, Piedra Buena, at ~2100-2500 m and Valentín Feilberg, at ~3500-4000 m) (Hernández- Molina et al. 2009, 2010; Gruetzner et al., 2011). They are composed of thick (up to 2000 m) plastered drifts that became mounded towards the deeper terrace. Contouritic processes are so important here that even the rise acquires a "contouritic" character rather than a typical base-of-slope gravitational feature. Southern Patagonia, islands and Scotia Arc (south of 49°S). Comprises the entire region that corresponds to the transcurrent, mixed and active margins, where more detailed studies are still lacking for differentiating sectors with distinct morphological and genetic characteristics. The configuration of this zone favors the occurrence of very significant gravitational processes in the steeper sectors of the slope both in the northern (Escarpa de Malvinas -Malvinas Scarp-) and in the southern side (flank of the Dorsal Norte de Scotia -North Scotia Ridge-). In the western side of the Arc, Lonardi and Ewing (1971) described at least seven submarine canyons. Contouritic drifts develop locally in the slope, and within depressions between structural heights and sea-floor elevations, where more energetic bottom currents are channeled. This is the case for the Fosa de Malvinas (Malvinas Trough) and for different passages connecting the Scotia Sea with the southwestern sector of the Argentine Sea (Cunningham et al. 2002; Pudsey and Howe, 2002; Rebesco et al., 2002; Maldonado et al., 2003, 2006, 2010; Koenitz et al., 2008; Baristeas et al., 2013; Rovira et al., 2013; Esteban, 2013; Pérez, 2014; Pérez et al., 2015). Contouritic drifts in these regions are mainly plastered, although mounded, elongated, detached and sheeted types are also recognized depending on their location and local morphology. Concluding remarks The progress in the scientific knowledge of the deep-sea sedimentation in the ACM has significantly advanced in recent years, through the change from a "gravity, density-dominated" model to an "alongslope, current-dominated" model. However, it must be considered that the two models are not opposite, but they coexist and interact. Two major areas can be differentiated in terms of the prevalent sedimentary processes. The passive margin is dominated by an extensive Contouritic Depositional System, whose complex architecture is characterized by a variety of depositional, erosive and mixed features interacting with large systems of submarine canyons and masstransport processes, with different configurations according to the zone and local morphosedimentary characteristics. On the other hand, in the transcurrent, mixed and active margins, contouritic drifts are regionally limited and in general located in more energetic regions such as passages between structural heights and sea-floor elevations. The advance in the knowledge and the understanding of the deep-sea processes in the ACM is not only relevant for the development of marine geological and sedimentological sciences but also in the field of Physical Oceanography. The study of contouritic bodies and their records is also useful for paleoenvironmental and paleoceanographic reconstructions. Applied aspects such as resources exploration, sea-floor instabilities, deep currents and their interaction with sea bed, as well as other items related to marine geohazards, will benefit from the integration between Marine Geology and Oceanography.Fil: Violante, Roberto Antonio. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval. Departamento Oceanografía; ArgentinaFil: Cavallotto, José Luis. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval. Departamento Oceanografía; ArgentinaFil: Bozzano, Graziella. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval. Departamento Oceanografía; ArgentinaFil: Spoltore, Daniela Veronica. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval. Departamento Oceanografía; Argentin