Structural control and tectono-sedimentary evolution of the Gulf of Cadiz, SW Iberia since the late Miocene: Implications for contourite depositional system

The Gulf of Cadiz Contourite Depositional System (GCCS) developed due to the interaction of the Mediterranean Outflow Water (MOW) with the middle continental slope of the SW Iberian continental margin. The GCCS evolved in a complex tectonic setting within the foreland of the Betic Orogeny and near the Nubia-Eurasia plate boundary. This study used tectonostratigraphic analysis of an extensive 2D multichannel seismic reflection dataset to investigate how inherited basin configuration and tectonic activity controlled sedimentary stacking pattern and evolution of the GCCS. Three regional tectonostratigraphic units (U1-U3) were recognised in the margin. The younger seismic unit U3 corresponds to the Miocene-Quaternary foreland basin system where the contourite system is generated. Seismic analysis also detected the dextral strike-slip Gil Eanes Fault Zone (described herein for the first time), the Cadiz Fault, the Albufeira-Guadalquivir-Don similar to ana Basement High and several diapiric structures. Integrated analysis of seismic profiles showing these tectonic structures with thickness and earthquake distribution maps suggest four tectono-sedimentary domains. The distinct characteristics shown by contourite features in the different domains, depends at broad-scale on the tectonic-control of the accommodation space (i.e., subsidence or uplift) and at local-scale on the presence of structural highs and fault-related depressions. Both influence bottom-current circulation and thus the evolution of the contourite deposits through the late Miocene and Quaternary. Three main stages have been recognised in the Gulf of Cadiz evolution: 1) the region was the western continuation of the Betic Corridor until the final re-opening of the Strait of Gibraltar (8-5.3 Ma). In this stage there is a predominance of turbidites or hemipelagic deposits, dependant on tectonic activity; 2) with the final re-opening of the Mediterranean-Atlantic connection there is the onset of the PlioceneQuaternary contourite depositional system (5.3-2.0 Ma). Short-term changes in sedimentation during this stage, from contourite to turbidite deposits, indicate periods of increased tectonic activity; and 3) after the onset of the transpressive tectonic regime in the area (from 2.0 Ma), sedimentation became more homogeneous suggesting stable conditions (decrease of tectonic activity) with dominant contourite deposition. This work highlights the remarkable influence of structural features and tectonic events in controlling the seafloor relief and in turn in influenced the local oceanic circulation processes that controlling the morphology and sedimentary evolution of contourite systems.info:eu-repo/semantics/publishedVersio

Late Quaternary multi-genetic processes and products on the northern Gulf of Cadiz upper continental slope (SW Iberian Peninsula)

On continental margins, the upper slope to shelf break environment forms a critical region where sediment supply, hydrographic activity and gravitational processes determine how and when sediments are partitioned between the shallow- and deep-marine realm. On the SW Iberian margin, relatively few studies have addressed the dynamics of this region, although it holds key information regarding the link between the sedimentary evolution of the continental shelf and the contourite depositional system on the middle slope. This work therefore presents a high-resolution analysis of the morphological and stratigraphic expressions of late Quaternary (dominantly last glacial and present-day interglacial) sedimentary processes on the upper slope and shelf margin sector between 7° and 7°30’ W. The integration of seismic, bathymetric and hydrographic data reveals the presence of alongslope processes and products (a bottom current-related plastered drift, moat, erosional surface and terrace, an internal wave-/tide-controlled sediment wave field), downslope (gravitational) processes and products (an upper slope – shelf margin valley system, slumps, debrites, gullies), neotectonic elements (diapirs) and fluid flow features (pockmarks, bright spots). The spatial distribution of these features indicates that the study area becomes increasingly alongslope-dominated towards the W, and oppositely, more downslope-dominated towards the E, because sediment supply to the latter area is enhanced under the dominant eastward dispersal of fluvially supplied sediments on the shelf. In addition, glacial-interglacial variations in the amount of sediments supplied to the shelf edge and the intensity of oceanographic processes in the study area also generate a distinct temporal variability, with glacial and interglacial intervals respectively recording principally downslope- and alongslope-controlled morphological elements. Finally, regardless of these overall spatial and temporal patterns, diapirism and fluid flow are inferred to locally destabilize sediments and induce small-scale mass wasting in the study area. These findings are not only relevant to the northern Gulf of Cadiz, but also to the general understanding of sedimentary dynamics and controls in mixed downslope- and alongslope-controlled upper slope to shelf margin settings worldwide.T. Mestdagh is funded through a doctoral scholarship of the Ghent University Special Research Fund (BOF). We would like to thank the captains, crews and scientists involved in research campaigns COMIC 2013 on board of RV Belgica and LASEA 2013 on board of RV Ramón Margalef. Ship time on RV Belgica was provided by BELSPO and RBINS-OD Nature. This research was performed in collaboration with ”The Drifters” Research Group of the Royal Holloway University of London (UK), and is associated to projects CTM 2012-39599-C03 , CGL2016-80445-R ‘SCORE’ ( AEI/FEDER , UE), CTM2016-75129-C3-1-R , CGL2011-30302-C02-02 and CTM2017-88237-P . Editor Michele Rebesco and two anonymous reviewers are kindly acknowledged for providing constructive feedback

Water mass footprints in uneven turbidite system development in the Alboran Sea

Multidisciplinary work between oceanography, geomorphology and sedimentology has uncovered evidence explaining the uneven development of the turbidite systems (TSs) in the Alboran Sea. Nine TSs have been mapped in the Spanish margin, ranging from sandy to mixed sand-mud fans, and which become sandier towards the Strait of Gibraltar; in contrast TSs do not develop in the Moroccan margin, where three canyons incise the continental slope but there is no TS formation. We interpret that the uneven development of TSs in the two margins and their variable architectures are conditioned by the interaction of alongslope with downslope processes. Two different interaction scenarios with varying intensities are proposed.Versión del edito

Review of the late Quaternary stratigraphy of the northern Gulf of Cadiz continental margin:New insights into controlling factors and global implications

Over the past decades, the northern Gulf of Cadiz has been the focus of a wide range of late Quaternary seismic and sequence stratigraphic studies, either addressing the slope contourite depositional system (CDS), or the development of the continental shelf. Yet, high-resolution seismic data bridging between these domains and age information have remained sparse. This study, based on new high-resolution reflection seismic profiles calibrated to IODP Expedition 339 sites U1386/U1387, now presents an updated stratigraphic framework, that integrates (for the first time) the late Quaternary records of the northern Gulf of Cadiz middle slope to shelf off the Guadiana River. Seismic stratigraphic analysis of the stacking, depocenter distribution, stratal architecture and facies of the seismic (sub-)units reveals the influence of similar to 100 kyr sea-level variations paced by Milankovitch (eccentricity) cycles, tectonics (manifesting as two pulses of uplift and margin progradation), sediment supply and bottom current activity. This work furthermore contributes to the application and understanding of high-resolution, late Quaternary sequence stratigraphy. Firstly, the proposed sequence stratigraphic interpretation shows that adaptations to the basic models are required to integrate the shelf and slope record, and to account for the presence of a significant alongslope (bottom current-controlled) component. Secondly, the results confirm that the sequences are dominantly composed of regressive deposits, whereas the preservation of transgressive to highstand deposits is more irregular. Significantly, the common assumption that successive major glacial lowstands are consistently recorded as well-marked, shelf-wide erosional unconformities, is demonstrated to be occasionally invalid, as tectonics can obliterate this one-to-one relationship

Oceanographic processes and morphosedimentary products along the Iberian margins: A new multidisciplinary approach

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Geomorphological and sedimentary processes of the glacially influenced northwestern Iberian continental margin and abyssal plains

The offshore region of northwestern Iberia offers an opportunity to study the impacts of along-slope processes on the morphology of a glacially influenced continental margin, which has traditionally been conceptually characterised by predominant down-slope sedimentary processes. High-resolution multibeam bathymetry, acoustic backscatter and ultrahigh-resolution seismic reflection profile data are integrated and analysed to describe the present-day and recent geomorphological features and to interpret their associated sedimentary processes. Seventeen large-scale seafloor morphologies and sixteen individual echo types, interpreted as structural features (escarpments, marginal platforms and related fluid escape structures) and depositional and erosional bedforms developed either by the influence of bottom currents (moats, abraded surfaces, sediment waves, contourite drifts and ridges) or by gravitational features (gullies, canyons, slides, channel-levee complexes and submarine fans), are identified for the first time in the study area (spanning ~90,000 km2 and water depths of 300m to 5 km). Different types of slope failures and turbidity currents are mainly observed on the upper and lower slopes and along submarine canyons and deep-sea channels. The middle slope morphologies are mostly determined by the actions of bottom currents (North Atlantic Central Water, Mediterranean Outflow Water, Labrador Sea Water and North Atlantic Deep Water), which thereby define the margin morphologies and favour the reworking and deposition of sediments. The abyssal plains (Biscay and Iberian) are characterised by pelagic deposits and channel-lobe systems (the Cantabrian and Charcot), although several contourite features are also observed at the foot of the slope due to the influence of the deepest water masses (i.e., the North Atlantic Deep Water and Lower Deep Water). Thiswork shows that the study area is the result of Mesozoic to present-day tectonics (e.g. themarginal platforms and structural highs). Therefore, tectonism constitutes a long-term controlling factor, whereas the climate, sediment supply and bottom currents play key roles in the recent short-term architecture and dynamics. Moreover, the recent predominant along-slope sedimentary processes observed in the studied northwestern Iberian Margin represent snapshots of the progressive stages and mixed deep-water system developments of the marginal platforms on passive margins and may provide information for a predictive model of the evolution of other similar margins.Departamento de Investigación y Prospectiva Geocientífica, Unidad de Tres Cantos, Instituto Geológico y Minero de España, EspañaDepartamento de Geología y Geoquímica, Universidad Autónoma de Madrid, EspañaDepartment of Earth Sciences, Royal Holloway University of London, Reino Unid

Subsurface Geophysics and Geology (GEOFSU

[EN] The geophysics line at the IGME began in 1927 as a Geophysics Sectiondedicated to subsurface exploration. During all this time, it has been developed in order to support and give expert service in all IGME’s activities both as a geological service and public research institution, as well as a research and development work itself. On the other hand, in recent years the IGME has promoted a line of research aimed at the characterization and 3D modeling of geological structures and formations, the development of dedicated software and the evolution and sophistication of computer equipment. The new scenario of incorporation of the IGME to the CSIC as a national reference center in the field of Earth Sciences has allowed the establishment of the GEOFSUB Research Group (Subsurface Geophysics and Geology). It is constituted by 21 members who had been collaborating regularly of the IGME former scientific-technic areas Geophysics and remote sensing (Área de Geofísica y Teledetección) and Subsurface geology and 3D geological modelling (Área de Geología del Subsuelo y Modelización Geológica 3D). Our main differentiating element is our extensive knowledge of geophysical and geological techniques, which allows us to characterize the subsoil in an optimal waPeer reviewe