In this work, we analyse the sediment particulate matter (SPM) dynamics. This subject is poorly understood in the Rias Baixas system (NW Iberian Peninsula), thus the bottom sediment dynamics of the inner sector of a ria is investigated for the first time. The current, turbidity, temperature and salinity were measured from 15 June to 17 July 2009, in the Ria de Muros-Noia, the northernmost embayment of the Rias Baixas. The parameters were measured by two moorings placed in the central axis of the inner sector; one equipped with two current meters, at 0.4 m and 1 m above the bottom (mab), and the second mooring equipped with one current meter at 0.4 mab. The wave data inside the ria during the survey was obtained using a numerical model (SWAN) computed from available wave data in open waters (provided by Organismo Publico Puertos del Estado, OPPE). The survey was characterized by upwelling and downwelling events and punctual precipitation periods. The mooring data revealed the alternation of different subtidal processes; deep-water upwelling, relaxation periods and a large downwelling. SPM of fluvial origin was transferred to the bottom from the surface under downwelling conditions, whilst the arriving of oceanic water under upwelling conditions showed lowest turbidity values. The subtidal circulation of the water masses inside the ria controlled mainly the bottom turbidity dynamics in the inner sector. The SW waves were likely to produce punctual resuspension in the shallowest areas, and the tidal currents only transported locally the SPM clouds when the subtidal circulation made it available in the bottom.

Deep-sea sediments record palaeoenvironmental and oceanographic changes over time through variations in their magnetochemical and sedimentological properties. This study presents the Late Quaternary sedimentary reconstruction of three sediment cores extracted from a source-to-sink sedimentary system located in a high marginal platform of the north-west Iberian Margin. The aim of this reconstruction is to explore the palaeoclimatic, palaeoproductivity and diagenetic changes over the last 172 cal ka bp attending to geochemical, magnetic and sedimentological variations. The record is comprised of four sedimentary units consisting of pelagic, hemipelagic and detrital facies, the latter associated with ice-rafted debris events at Heinrich Stadials. These findings allowed the reconstruction of the lithostratigraphy attending to climatic changes, covering the last eleven Heinrich Stadials. These units and facies successions are controlled by the superposition of the Milankovitch and Dansgaard-Oeschger cycles. Low sedimentation rates have been reported, especially during cold periods. Palaeoproductivity was assessed using total organic carbon and calcium carbonate content, together with biogenic barium (Ba-bio) and organic phosphorus (P-org), both calculated via total digestion analysis using standard calculations. Mass accumulation rates for total organic carbon, Ba-bio and P-org were calculated. Furthermore, a sequential extraction was performed to explore the different phases of the barium within sediments: biogenic barite (Ba-bar), barium associated with iron and manganese oxides (Ba-ox) and Ba associated with aluminosilicates (Ba-det). Results display a limitation in the use of the biogenic barium and phosphorus and mass accumulation rates, suggesting detrital Ba (Ba-detr) contribution during Heinrich Stadials, which could mask the calculations. In contrast, only calcium carbonate fluctuates attending to glacial/interglacial cycles. Regarding some diagenetic proxies (i.e. Mn, Mn/Fe and Mn/Ti), they reveal oxidation fronts of different generations, suggesting that the early diagenesis has not reached steady-state, because the redoxcline fluctuates. This fact suggests an erosional activity that causes the continuous oxygenation of the sediment and non-steady-state conditions.

Studies of the most surficial sedimentary record from passive continental margins provide crucial knowledge about sedimentary dynamics and its changes through recent geological times. These studies allow understanding in detail the influence of both tectonic activity and long-term bottom-current circulation over the Late Quaternary sedimentary dynamics. Using a large dataset of multibeam bathymetry, chirp and multi-channel seismic (MCS) records, ROV seabed direct observations and a magneto-chemical facies characterisation, we provide a well-dated record of the tectono-sedimentary processes on an isolated high marginal platform over the Late Quaternary. Our results display several structural and geomorphological features and tectonic pulses that indicate intense faulting, folding, and deformation of the most recent sedimentary cover. Furthermore, we document four main sedimentary systems acting at the study area and controlled by different water masses (MOW, LSW and NADW): the (hemi)pelagic, bottom current-controlled (hemi)pelagic, contourite and downslope sedimentary systems; as well as a new typology of contourite associated to giant depressions, named as pockmarks-related drift. The record also shows erosive features and extremely low sedimentation rates for the last 172 cal ka BP. Results suggest that the topographic configuration of the high marginal platform and reorganizations of the water masses associated to climate changes causes a constriction of the water masses that induce an enhancement of the bottom-current activity, favouring erosion, winnowing and redistribution of sediments. Therefore, this study provides new insight into the tectonic control and bottom current activity effect over the Late Quaternary sedimentary cover from an isolated and elevate offshore morphostructural province, located at the Galician Continental Margin.

Surficial sediments on the seafloor from passive continental margins can provide insight into recent Late Quaternary sedimentary dynamics acting over offshore sedimentary systems. This work focuses on the study of some particular ferruginous tubular structures resembling bioforms (FTB) located in the distal Galician Continental Margin (NW Iberian Margin) at water depths between ~ 1550 and ~ 2200 m. The characterisation of these structures made it possible to study in depth their formation environment and subsequent sedimentary evolution during the Late Pleistocene and Holocene. The FTB consist of goethite with a framboidal texture. They were interpreted as formed by an initial pyrite precipitation in reducing microenvironments conditioned by the activity of sediment-dwelling organisms during the early diagenesis. This is followed by the oxidation of pyrite by a combination of hydrothermal fluids and erosional processes, which triggers the formation of the framboidal oxyhydroxides. The data allowed obtaining a comprehensive understanding of the environmental context and the significance of these ferruginous tubules, as there are no previous studies in the scientific literature that describe these structures in a source-to-sink sedimentary system.

When an oil spill occurs, a prompt response reduces significantly the impact. The preparedness and contingency plans are essential to identify the most appropriate technologies. Unmanned and autonomous vehicles (UAVs) is emerging as a powerful tool of strategic potential in the observation, oil tracking and damage assessment of an oil spill. The SpilLess project explored the suitability of these devices to be the first-line response to an oil spill. This work analyses the operational requirements related to environmental parameters following a two steps approach: 1) Environmental characterization from long wind and waves time series and modelling; 2) Definition of the optimal periods for operating each UAVs. We have defined the periods in which each of these facilities acts best, confirming that the operational limits of UAVs are not significantly more restrictive than the traditional operations. UAVs should be included in contingency plans as available tools to fight against oil spills.

The Ria de Vigo (NW Iberian Peninsula) is one of the most impacted coastal areas of Galicia, due to demographic and industrial pressure. One of the main consequences of this pressure is the need to extend the current wastewater treatment plant of the city of Vigo (295,000 inhabitants). This extension includes a new submerged pipeline construction to discharge the treated water in the central channel of the Ria. The new planned pipeline must cross Samil Beach, the most important urban beach of the city. Based on a multitool strategy, this work characterizes the interactions between the new pipeline route alternatives and the sediment dynamics of Samil Beach. This approximation improves the reliability of the results in the subtidal area of the beach, where studies are scarce due to the complexity of the data acquisition. The present study is based on high resolution bathymetry data, seabed physical characterization, a granulometric study of the superficial sediment, and a numerical simulation of the tide, wave climate, and sediment transport in low and high energy conditions using open source Delft3D software. The results showed that the area of interest is a low energy area, which is significantly shielded from wave attack, where fine sand predominates. However, the field data indicated an interaction (accretion-erosion) in the submerged obstacles between 0 and 12 m deep. The model revealed that there is significant sediment movement above a 7.4 m isobath, and that the pipeline would not alter the general transport dynamics of the beach, but would interact in the shallowest section. The main conclusion of this work states that the future structure would not alter the global sediment dynamics of the beach. In addition, in order to guarantee the safety of the new pipeline, it should emerge above an 8 m isobath. The multiapproach methodology presented can be applied to other studies of the interaction between coastal structures and the environment.

Textural, geochemical and geochronological analyses on two gravity and two box cores recovered from the outer and inner sectors of the Ria de Muros allowed reconstructing and timing the anthropogenic imprint on the sedimentary record from this ria. The chronological framework for the last 8 kyr was built based on Pb-210 dating (Constant Rate of Supply model) and C-14 dating. Recent sedimentation rates were an order of magnitude higher than those of the oldest analyzed sediments, and the periods of upwelling enhancement were constrained. Assessing the human influence on sediment metal contents required the establishment of local background levels. Since the 16th century the enrichment factors of copper, zinc and lead increased (up to 2.7, 1.5 and 2.1, respectively, at or close to present), and a remarkable increase in the fine-grained particles' content happened in the outer ria sector, due to deforestation. The anthropogenic signature identified in the sedimentary record is assigned to fishing, harbor activities, mining, salting, and, or canning activities, depending on the considered period, which caused a local demographic increase since the 16th century in the region. Such population growth caused a rise in the marine signature of the organic matter, which likely results from enhanced primary production due to eutrophication caused by increased soil erosion and human and livestock waste inputs. Furthermore, the metal enrichment trend during the 20th century, which was more significant in the inner than in the outer ria sector, follows the different demographic evolution of the villages (related to urban and industrial development). The present study highlights the need for conjunction of varying dating techniques when reconstructing the anthropization trends in coastal environments.

Large national programs in the United States and several Asian countries have defined and characterised their marine methane hydrate occurrences in some detail, but European hydrate occurrence has received less attention. The European Union-funded project “Marine gas hydrate – an indigenous resource of natural gas for Europe” (MIGRATE) aimed to determine the European potential inventory of exploitable gas hydrate, to assess current technologies for their production, and to evaluate the associated risks. We present a synthesis of results from a MIGRATE working group that focused on the definition and assessment of hydrate in Europe. Our review includes the western and eastern margins of Greenland, the Barents Sea and onshore and offshore Svalbard, the Atlantic margin of Europe, extending south to the northwestern margin of Morocco, the Mediterranean Sea, the Sea of Marmara, and the western and southern margins of the Black Sea. We have not attempted to cover the high Arctic, the Russian, Ukrainian and Georgian sectors of the Black Sea, or overseas territories of European nations. Following a formalised process, we defined a range of indicators of hydrate presence based on geophysical, geochemical and geological data. Our study was framed by the constraint of the hydrate stability field in European seas. Direct hydrate indicators included sampling of hydrate; the presence of bottom simulating reflectors in seismic reflection profiles; gas seepage into the ocean; and chlorinity anomalies in sediment cores. Indirect indicators included geophysical survey evidence for seismic velocity and/or resistivity anomalies, seismic reflectivity anomalies or subsurface gas escape structures; various seabed features associated with gas escape, and the presence of an underlying conventional petroleum system. We used these indicators to develop a database of hydrate occurrence across Europe. We identified a series of regions where there is substantial evidence for hydrate occurrence (some areas offshore Greenland, offshore west Svalbard, the Barents Sea, the mid-Norwegian margin, the Gulf of Cadiz, parts of the eastern Mediterranean, the Sea of Marmara and the Black Sea) and regions where the evidence is more tenuous (other areas offshore Greenland and of the eastern Mediterranean, onshore Svalbard, offshore Ireland and offshore northwest Iberia). We provide an overview of the evidence for hydrate occurrence in each of these regions. We conclude that around Europe, areas with strong evidence for the presence of hydrate commonly coincide with conventional thermogenic hydrocarbon provinces.

Ferruginous tubular structures concretions are widely distributed over the seafloor surrounding the Gran Burato depression in the Transitional Zone (TZ) province of the Galician Continental Margin (NW Iberian Margin). These bioforms-like structures are created by iron oxides precipitations into the tube-dwelling macrozoobenthos as a result of Fe2+ upward diffusion and O2 ventilation and diffusion acting in the water-sediment interphase in a non-steady state early diagenesis. X-ray diffraction analyses display that goethite is the main mineralogical component of these bioforms-like structures. Furthermore, non-steady state diagenesis has been identified by several oxidations fronts recognised in three piston cores, reflecting that the redoxcline has not achieved the deeper equilibrium in the study area. Afterwards, these ferruginous tubes were eroded, remobilised and redistributed over the seabed by bottom currents. Ocean-floor observations show erosion and sea-bottom current structures as ripples, grooves, erratic blocks, accumulations of pteropods and carbonate crusts associated with hardgrounds. Sedimentation rates calculated in a piston core display very low values for the last 30 cal ka BP (mean of 1.57 cm ky−1) with a marked hiatus between 17.80 to 10.45 cal ka BP, meanwhile abraded surfaces have been identified by high-resolution seismic data confirming erosional processes in this area of the TZ province. We conclude that the ferruginous bioforms accumulation over the deep-ocean floor is indicative of a present-day vigorous seafloor current acting and eroding the sediments of the TZ province. This bottom current is a direct consequence of the general seafloor elevation of the TZ province that causes constriction of the water masses (MOW and LSW) that induces a general intensification of the bottom currents and greater erosional capacity. This erosional process causes the continuous oxygenation of the upper sediments, and it prevents to reach the steady-state diagenesis, playing this fact an essential role in the ferruginous formations and accumulations in the study area.

This work analyzes the results of the SP2 core (50.30 m length) collectedin the coastal plain of Sepetiba Bay (SB; SE Brazil), 2 km away from the Guandu River mouth (latitude 22° 55′S, longitude 43° 46′W). It aims to study the influence of the Holocene relative sea level (RSL) on the coastal plain of SB. After description, the SP2 core was sampled at every 5 cm for grain size, geochemical, mineralogical and foraminiferal analyses. Four radiocarbon dates obtained in the first 18 m were modulated with Bayesian statistics. The SP2 core is composed of basement rocks, gneisses (50.30–43.80 m); river sediments (43.80–21.00 m) up to about ≈ 5.0 kyr BP; a sediment package marked by sudden textural and compositional changes, accumulated between ≈ 5.0 and 4.7 kyr BP; muddy sediments deposited between 4.7 and 0.8 kyr BP (18.80–3.35 m) with intercalations of sandy levels; an upper part of disturbed embankment sediments used for the implantation of Santa Cruz Thermoelectric Power Plant. The fluvial sands accumulated before ≈ 5.0 kyr BP were deposited before the maximum Mid-Holocene relative sea level. They were probably eroded and transported by the drainage network of the N region of SB, namely by the Guandu River. Between ≈ 4.5 and 3.5 kyr BP, the foraminiferal abundance and assemblage composition indicate that the study site was a shallow marine environment, due to the Mid-Holocene relative sea-level highstands (MHSLH). Between ≈ 3.5 and 3.0 kyr BP, the sediment accumulation rate (SAR) was the lowest of the last ≈ 5 kyr BP and the study site was exposed to subaerial weathering processes, in a scenario of the relative sea-level drop. A new phase of marine influence was recorded between ≈ 3.0 and 1.9 kyr BP, associated with the highest SAR of this record, up to ≈ 27.4 m/kyr BP. Between ≈ 1.9 and 1.8 kyr BP, the study site was under subaerial weathering processes. Since then the SAR reduced significantly to a mean value of ≈ 4.5 m/kyr and, between ≈ 1.8 and 0.8 kyr BP, the study site was again under the marine influence. Foraminifera were not found, after ≈ 0.8 kyr BP, in the SP2 core. However, the occurrence of a shallow marine environment was identified in another core, between ≈ 1.4 and 0.35 kyr BP, in the Guaratiba Mangrove, NE of SB. The results of the SP2 core suggest that MHSLH left a striking record in the study area, although some of the identified environmental changes are probably related to adjustments of the lower course of Guandu River and tidal channels and variations in the configuration of sandy littoral strands. The growth of a barrier–island system, the Marambaia barrier island, since the last ≈ 8–7.5 kyr BP may also have induced changes in the study area.

The validity and usefulness of multivariate statistical tools for the facies characterization in deep-marine environments have been applied on the geochemical, sedimentological and magnetic data from a piston core extracted from the Transitional Zone in the Galician Continental Margin. The combination of geochemical profiles of Fe, Mn, Ti, Ba and Ca and magnetic susceptibility (MS) obtained using the ItraxTM Core Scanner at the University of Vigo, together with the grain-size, grey level and R (red) G (green) B (blue) colour analyses have allowed characterizing and classifying the sediments of the core PC13-3 using SPSS package v. 23. Cluster Analysis (CA) displays, in the first level of the hierarchy, two major groups that correspond with clay-silt and sand facies. In a second level, it is possible to observe six subfacies that match de visu preliminary classification and allowed us to complete and improve the characterization and the facies limits in the whole core. Discriminant Analysis (DA) confirmed the validity of the cluster analyses and enhanced the results of the classification. The Principal Component Analysis (PCA) shows four principal components: coarse lithogenic fraction (PC1), fine lithogenic fraction (PC2), high density fraction (PC3) and biogenic fraction (PC4). These results are in concordance with the Pearson correlation coefficient and the SEM observations. In general terms, the results confirm the utility of the multivariate statistical methods applied on high resolution geochemical and magnetic data acquired with ItraxTM corer scanner, as a quick and complementary tool in sedimentary facies analysis and description in deep marine environments.

The Ria de Vigo (NW Spain) is an economically important coastal system in which increasing demographic pressure over the last four decades has led to the development of conflicting economic activities, such as industry, fisheries, and tourism. The bottom sediment dynamics in the ria were investigated here for the first time as a key element to address effective coastal management in this context. The turbidity, salinity, temperature, and current were measured by two current meters placed at similar to 1 m above the bottom (mab) during 14 days from 28 June 2005 to 11 July 2005. Both stations were placed in the marine sector of the ria, one in the central channel and the other in the outer southern margin. Superficial sediment samples in the surroundings of each site were also analyzed. The survey occurred under low-wave (significant wave height [Hs] < 2 m) conditions with little precipitation, typical of the summer season. The oceanographic observations registered the complete development of an East North Atlantic Central Water (ENACW) upwelling event in the ria. The results indicated that the main suspended particulate matter (SPM) fluctuation was produced in the subtidal timescale and correlated well with the upwelling-produced inward current, rather than with the dominant hydrodynamic processes (tide and waves) at the sampling sites. Punctual, but significant input from runoff was also detected in the channel. Under summer conditions, the advection of the shelf SPM by the upwelling bottom current stands out as the main transport process observed in the marine sector of the ria.

This work combines planktonic foraminiferal assemblages, stable isotope, transfer function estimated sea surface paleotemperatures (SST) and export productivity (Pexp) with sedimentological records from the PC7 core to document paleoclimatic and paleoceanographic changes on a distal region of the NW Iberian Margin since the last glaciation (<approximate to 68 ka). Neodymium and strontium isotope data are also used to identify the provenance of ice rafted debris (IRD) during Heinrich event 5 (H5). Our results are compared and combined with previously published records and evidence that melt water and icebergs from the Canada, Greenland, Iceland and Europe ice sheets arrived to the NW Iberian Margin causing a significant decrease of SST during the last six Heinrich Stadials (HS) and some Dansgaard-Oeschger (D-O) stadial events. epsilon Nd and Sr-87/Sr-86 indicate that the studied locality mostly received sediments from European Ice Sheets (EIS) during H5. During the HS and D-O stadial events, SSTs were in general higher than in other cores collected in inner areas of the NW Iberian Margin. The presence and intensification of Portugal Current probably induced heat transfer to this distal region of the Iberian Margin. Our results also suggest the occurrence of high variability in the intensity and wind patterns during the last glaciation. In some periods, the intensity of northerly winds could have been very strong and contributed to a significant stimulation of ocean productivity in this distal area through the intensification of upwelling. In general, oceanic productivity decreased during the HS and D-O as the presence of cold and less saline water prevented nutrient rich waters from deep levels reaching the surface. The high productivity events were bracketed by periods characterized by the highest influence of the Azores Current eastern branch during which northerly winds and the oceanic productivity should have been weakened.

Recent studies have demonstrated that rock‐magnetic analysis may provide additional information to distinguish and characterize extreme marine inundation events such as tsunamis. Rock‐magnetic proxies reinforce and improve the environmental evidences supplied by other methods, adding some decisive clues for the interpretation of the origin and genesis of the sedimentary deposits. Here we report rock‐magnetic, XRD, and SEM microscopy results obtained in the Palo Verde estuary (Colima Pacific coast, Mexico) in order to enhance the tools for identification and reconstruction of two tsunami‐induced deposits. The sedimentary sequence includes two sand units, a tsunami deposit (PV1) associated with the 22 June 1932 tsunami and a deeper sandy layer (PV2) related to a possible paleotsunami that occurred around 1300 C.E. Both sandy units are topped by finer grained units. Magnetic properties exhibit a significant correlation with the stratigraphy. High susceptibility (χ) and high saturation isothermal remanence (SIRM) values typical of high concentrations of (titano)magnetite are a distinctive feature of the most recent sandy tsunamigenic unit PV1 and the overlaying soil. The lower sandy tsunamigenic unit PV2 shows significantly lower χ and SIRM values, indicating lower concentration of (titano)magnetite in this unit and the overlaying clayey‐silt unit. The latter also shows a higher coercivity component associated with (titano)hematite. Magnetic grain‐size differences are also observed between PV1 and PV2 suggesting differences in hydraulic conditions at the time of deposition. The bulk mineralogical composition and sediment texture of these units also support the hypothesis of different provenances for each tsunamigenic unit as inferred from magnetic properties.