Understanding the complex geomorphology of a deep sea area affected by continental tectonic indentation: The case of the Gulf of Vera (Western Mediterranean)

19 pages, 11 figures, 1 table, supplementary data https://doi.org/10.1016/j.geomorph.2022.108126.-- Data availability: Casas, D., & UTM-CSIC. (2018). FAUCES-1 Cruise, RV Sarmiento de Gamboa [Data set]. UTM-CSIC. doi: 10.20351/29SG20170925 Comas, M. & UTM-CSIC. TOPOMED-GASBATS. Cruise, RV Sarmiento de Gamboa [Data set]. UTM-CSIC.doi: 10.20351/29SG20120517We 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 plainThis research has been funding by the Spanish projects: DAMAGE (CGL2016-80687-RAEI/FEDER) and FAUCES (CTM2015-65461-C2-1-R); and the Junta de Andalucía projects: RNM-148 (AGORA) P18-RT-3275 and PAPEL (B-RNM-301-UGR18). [...] This work acknowledges to IGCP 640 - S4LIDE (Significance of Modern and Ancient Submarine Slope LandSLIDEs), and to the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S

Global monitoring data shows grain size controls turbidity current structure

The first detailed measurements from active turbidity currents have been made in the last few years, at multiple sites worldwide. These data allow us to investigate the factors that control the structure of these flows. By analyzing the temporal evolution of the maximum velocity of turbidity currents at different sites, we aim to understand whether there are distinct types of flow, or if a continuum exists between end-members; and to investigate the physical controls on the different types of observed flow. Our results show that the evolution of the maximum velocity of turbidity currents falls between two end-members. Either the events show a rapid peak in velocity followed by an exponential decay or, flows continue at a plateau-like, near constant velocity. Our analysis suggests that rather than triggers or system input type, flow structure is primarily governed by the grain size of the sediment available for incorporation into the flow

Cronoestratigrafía del Cuaternario Superior del sector noroccidental del Mar de Alborán

Proyecto de Máster presentado por Maria Azpiroz Zabala para la obtención del Máster en Ciencias del Mar: Oceanografía y Gestión del Medio Marino de la Universitat de Barcelona (UB), realizado bajo la dirección de Belén Alonso Martínez y Gemma Ercilla Zárraga del Institut de Ciències del Mar (ICM-CSIC)Peer Reviewe

Submarine channels and biology

This dataset comprises ADCP and CTD data, and grab sample photographies and sedimentological analysis results. All data were collected in two oceanographic cruises on the shallow Black Sea shelf, to the North of the Strait of Bosphorus. During the first cruise on board the RV Koca Piri Reis in 2010, grab samples were recovered from the seafloor. During the second cruise on board the RV Pelagia and RV Bilim in 2013, bathymetry data, flow measurements (ADCP) and conductivity temperature depth (CTD) probes were collected

Newly recognized turbidity current structure can explain prolonged flushing of submarine canyons

Seabed-hugging flows called turbidity currents are the volumetrically most important process transporting sediment across our planet and form its largest sediment accumulations. We seek to understand the internal structure and behavior of turbidity currents by reanalyzing the most detailed direct measurements yet of velocities and densities within oceanic turbidity currents, obtained from weeklong flows in the Congo Canyon. We provide a new model for turbidity current structure that can explain why these are far more prolonged than all previously monitored oceanic turbidity currents, which lasted for only hours or minutes at other locations. The observed Congo Canyon flows consist of a short-lived zone of fast and dense fluid at their front, which outruns the slower moving body of the flow. We propose that the sustained duration of these turbidity currents results from flow stretching and that this stretching is characteristic of mud-rich turbidity current systems. The lack of stretching in previously monitored flows is attributed to coarser sediment that settles out from the body more rapidly. These prolonged seafloor flows rival the discharge of the Congo River and carry ~2% of the terrestrial organic carbon buried globally in the oceans each year through a single submarine canyon. Thus, this new structure explains sustained flushing of globally important amounts of sediment, organic carbon, nutrients, and fresh water into the deep ocean

ROV footage and high-resolution bathymetry for understanding the dynamics of the submarine Garrucha-Almanzora canyon systems

34th International Association of Sedimentologists (IAS) Meeting of Sedimentology, Sedimentology to face societal challenges on risk, resources and record of the past, 10-13 September 2019, Rome.-- 1 pageThe Garrucha and Almanzora are the northern tributaries of the submarine canyon system called Almanzora-Alías-Garrucha located in the Palomares continental margin (Southwestern Mediterranean Sea). The tributary system is deeply incised in the continental shelf that is 5 km wide and extends down to 100¿120 mwd, where the transition towards the upper continental slope starts.Multiple multibeam echosounder datasets were used to characterize this study area. 50 m resolution bathymetry data belonging to the Spanish General Secretariat of Fisheries (SGP) was merged with data recorded in the framework of the FAUCES project in order to produce high-resolution maps (10 to 2 m grid size resolution). The higher resolution data was recently collected onboard the vessel Sarmiento de Gamboa using an Atlas Hydrosweep DS and Kongsberg-Simrad EM2040 operated from the AUV AsterX. Accurate seafloor video imaging was recorded by an ARGUS ROV system. The Garrucha tributary erodes completely the continental shelf: its shallowest part reaches the infralittoral at 7-20 mwd. The Almanzora tributary is narrower and less incising: its head is located at 65¿90 m and affects the outer prodelta of the Almanzora River. In both cases a dense network of dendritic gullies along their flanks can be observed. After the convergence of the tributaries at 1100 mwd, the submarine canyon becomes wider and shows a meandering pattern. The ROV surveyed 7 nautical miles along the canyon axis at depths between 1100 and 1653 m. The images reveal a changing environment within this shelf-slope system. The ROV system recorded a great variability of depositional and erosive features such as sedimentary instabilities (isolated blocks, topples and falls) and bedforms. All these observations suggest that the tributary system funnel sediments from the coastline and shelf down to the deep sedimentary system, and also that the canyon system can act as a sediment source/reservoir in two ways: 1) sediment eroded from the canyon walls and 2) sediment released to the distal canyon after it has been temporarily deposited on the canyon floo

Bedforms in the la Linea Turbidite System (NW Alboran Sea)

34th International Association of Sedimentologists (IAS) Meeting of Sedimentology, Sedimentology to face societal challenges on risk, resources and record of the past, 10-13 September 2019, Rome.-- 1 pageThis work focuses on the study of the bedforms identified in different sectors of the La Linea turbidite system (NWAlboran Sea). The objective is to characterise the geomorphology and morphometry of these bedforms and determine their origin. The data set for this study consists of: i) bathymetric data acquired with a Konsgberg-Simrad EM-710 multibeam echosounder and an autonomous underwater vehicle (AUV idefX), enabling the generation of 15x15 m and 2x2 m bathymetric grid models, respectively; and ii) very high-resolution seismic profilesacquired withTOPAS PS18.The La Linea turbidite system comprises four architectural elements (canyon, channel, overbank, and lobe deposits) that have developed from the continental shelf (15 m water depth (mwd)) towards the basin (835 mwd). It can be divided into three sectors, based on average slope gradients and morphological elements. The upper sector (15-460 mwd) is characterised by high gradient slopes (4.5º) where the head canyon presents two branches, in addition to slides and scars. The middle sector (460-715mwd) has a less-steep slope (3.5º) and presents a zigzag channel course flanked by terraces on both sides. Lastly, the distal sector (715- 835 mwd) has the lowest gradient (1.88º), and is where the lobe deposits have accumulated.The AUV and regional bathymetry have led to the identification of two types of bedforms, asymmetric crescents and sinuous shapes, in the middle and distal sectors. These bedforms are typically detected as small diffractions on very high-resolution profiles, and there are no sub-bottom reflectors below them. Crescent bedforms. A total of 148 asymmetric bedformshave been measured on the turbidite channel floor, from 535 to 715 mwd. They are orthogonal to the channel, with wavelengths of between10 and 80 m and wave heights varying from 0.4 to 5 m. Downstream in the channel (in the channel-lobe transition), the bedforms are larger and display more erosive characteristics (i.e., enclosed depressions). Sinuous bedforms.Around 30 features have been identified on the terraces characterising the middle sector; they are smaller tan the bedforms detected within the channel (wavelengths of 5 to 20 m and heights of 0.2 to 1.5 m). In addition, the lobe deposits present several, large, unconfined sinuous bedforms (wavelengths of hundreds of metres and heights of 1 to 4 m).The bedforms identified in this turbidite system are related to turbidity currents funnelled through the canyon-channel. Crescent bedforms migrate upstream and could be related to supercritical flows or the transition from subcritical to supercritical flows (hydraulic jumps in the channel), which are very common in active canyons and zones with high slope gradients. However, the sinuous bedforms on the terraces and the distal lobe could be associated with different turbidity flows (subcritical flows). The existence of these features may be an important clue for understanding how sediment moves throughsubmarine canyon-channels and the degree of activity of the canyon-turbidite channel systemContribution from Projects FAUCES CTM2015-65461-C2-R (MINECO/FEDER founding, Spain) and VIATAR (IEO Spain

Bedforms and sedimentary processes along the Garrucha and La Linea canyon axis (SW Mediterranean Sea)

5th International Network for Submarine Canyon Investigation and Scientific Exchange International Symposium (INCISE), 14-18 June 2021The combination of high resolution bathymetry, seismic (parametric) and image (hull mounted & AUV multi-beam echo sounders, parametric profilers, ROV) records have allowed to describe the morphological elements and sedimentary processes that characterise the axis of two submarine canyons located in the SW Mediterranean Sea: The Almanzora-Alias-Garrucha canyon (Palomares Margin) and La Linea (Alboran Margin). The statistical analysis of morphometric parameters together with acoustic facies characterization allowed to establish three general types of bedforms in both systems. A) quasi-symmetric, B) upslope asymmetrical and C) downslope asymmetrical. These bedforms are interpreted as cyclic steps, formed by turbidity flows. They would be related to the important rivers/streams discharges favoured by the proximity of the canyon heads to the coast and erosion of canyons margins. The general gradient of the canyons axes and characteristics of the turbidity flow (energy, sedimentary load) seem to exert the main control. The morphological comparison of ¿cyclic steps¿ in both canyons indicates that the downslope asymmetrical forms would be associated with higher energy flows and the upslope asymmetrical forms with lower energy flows. It also points out that their formation would be related to muddy turbidity flows in the Almanzora-Alias-Garrucha canyon and sandy/silty flows in La Linea. The spatial variability of the cyclic step in each canyon could respond to the coexistence of today/subrecent bedforms with deeper relict forms formed during the last period of low sea leve

Slope stabilityof the Guadiaro-Baños contourite drifts (SW Mediterranean)

X Simposio sobre el Margen Ibérico Atlántico - X Simpósio sobre a Margen Ibérica Atlántica, 7-9 de julio de 2022, BilbaoLarge Quaternary plastered drifts characterise the slope and base of slope of the area between the Guadiaro and Baños turbidite systems (Alboran Sea). A terraced contourite drift has developed between 190 and 600 meters water depth (mwd). Seawards, another plastered drift extends from a scarpat 600 mwd to beyond the base of slope. The sedimentary and physical properties of the contourite drifts allowed establishing a geotechnical model that reveals high factors of safety. The sediments evolve from granular, low plasticity and very poorly sorted on the contourite terrace to medium-to high-plasticity, low-permeability and poorly sorted silty clayey-sediments on the distal contourites at the base of slope. These characteristics are consistent with the geotechnical model defined by the in-situ properties and SBT (Soil Behaviour Types) classification. The coarse-grained sediments, are defined by cohesion (c′) and internal friction angle (ϕ′)values of0-9 kPa and 46-30º, respectively. The undrained shear strength gradient (∇Su) is 2 kPa/m for distal contourites. These properties allow assessing high factors of safety (FoS), for all the scenarios considered, including seismic loading. Several characteristics and processes may explain the high stability compared to others with similar sedimentary features. These include 1) the geometry of the drifts, defined by an upper contouritic terrace and low-mounded cross-sections; and 2) recurrent low intensity earthquakes and cyclic loading induced by internal waves, both favouring the dynamic compactionThis research was supported by the Spanish Fauces project (CTM2015-65461-C2-1-R). This work acknowledges the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S). We are also grateful for the data we received from the Viatar project (http://datos.ieo.es/)Peer reviewe

Input files of validated simulations of 3D turbidity currents Delft3D4

Input files of validated Delft3D4 models of three-dimensional turbidity currents at laboratory and field scales that simulate laboratory-scale turbidity currents in previously published works