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

Contourite drifts in the Madeira Abyssal Plain and implications to the Northeast Atlantic deep water circulation during the Cenozoic

Simposio sobre el Margen Ibérico Atlántico (9º. 2018. Coimbra, Portugal)Several contourite drifts located in the Northeast Atlantic, westwards off the Madeira Island, were recognized below 4000 m water depth. They were studied by seismic stratigraphic interpretation of multichannel seismic lines and correlation with ODP Sites 950, 951 and 952. Three major stages in the sedimentary successions ranging in age from Late Cretaceous to Quaternary were identified above Cretaceous oceanic crust; a pre-drift,an initial-drift, and recent-drift stages. They are separated by erosive surfaces which represent unconformities interpreted as periods of enhanced bottom-current activity. The most probable water mass responsible for the deposition of these contourite drifts in the middle Cenozoic is the northwards flowing Southern Component Water, a proto-Antarctica Bottom Water.Estrutura de Missão para a Extensão da Plataforma Continental, PortugalInstituto Dom Luíz, PortugalDepartment of Earth Sciences, Royal Holloway University of London, Reino UnidoInstituto Geológico y Minero de España, Españ

Investigating Miocene Mediterranean-Atlantic Gateway Exchange (IMMAGE) - an amphibious drilling proposal

European Geosciences Union General Assembly (2017. Viena)Today Mediterranean seawater flows out through the Gibraltar Straits, forming a saline plume at intermediate depths in the Atlantic. The plume’s sedimentary record of distinctive, contouritic deposits has recently been recovered during IODP Leg 339 in the Gulf of Cadiz documenting a Mediterranean contribution to Atlantic thermohaline circulation since the Pliocene. However, before the Pliocene, the conduit for Mediterranean-Atlantic exchange is unclear. Gibraltar may have already been open, but two additional marine corridors also existed through northern Morocco and southern Spain. The restriction and closure of these Miocene connections resulted in extreme salinity fluctuations in the Mediterranean, leading to the precipitation of thick evaporites. This event is known as the Messinian Salinity Crisis (MSC) and recovering a complete record of the MSC is the target of current IODP drilling proposals (e.g. DREAM). Understanding both the causes of high-amplitude salinity change in the Mediterranean and its global consequences for thermohaline circulation in the Atlantic is dependent on recovering a complete record of Mediterranean-Atlantic exchange before, during and after the MSC. This key objective of the IMMAGE drilling proposal requires core recovery on-shore at the mouths of the Betic and Rifian corridors which are now exposed on land, as well as offshore, in the Alborán Sea and on the Atlantic continental margin. Consequently to meet this objective, an amphibious drilling strategy is necessary, involving both IODP and ICDP targets. In addi tion to allowing us to reconstruct Mediterranean-Atlantic exchange during high amplitude salinity fluctuations and identify the conduit through which exchange occurred, the sediments recovered from IMMAGE drilling will also provide us with a unique and explicit test for ocean physics hypotheses describing the location, size and velocity of overflow plumes under conditions where the density contrast between the two water bodies is up to two orders of magnitude higher than today.School of Geographical Sciences, University of Bristol, Reino UnidoInstituto Geológico y Minero de España, Españ

Análisis de lineamientos en el Margen Continental de Galicia y en las llanuras abisales adyacentes a partir del Modelo Digital del Terreno: Implicaciones en la evolución morfoestructural

Para identificar las principales estructuras tectónicas recientes existentes en el Margen Continental de Galicia y en las llanuras abisales adyacentes, se ha realizado un análisis cuantitativo de las orientaciones y longitudes de estructuras lineales que tienen expresión batimétrica en el fondo marino. Se han identificado unos 5800 lineamientos a lo largo de toda la zona de estudio. El mayor número de lineamientos se sitúa en la zona de los altos de Charcot y Coruña, en el sector occidental de la zona del Banco de Galicia, en la zona de las plataformas marginales y en el sector septentrional del margen. El análisis de la orientación de los lineamientos muestra una dirección NE-SO dominante y tres máximos relativos de dirección NO-SE, E-O y N-S. La longitud de los lineamientos identificados supera los 44.000 kilómetros. Se observa una moda en torno a 5000 metros y una longitud media de aproximadamente 7800 m. Basándonos en diferentes estudios tectónicos realizados en el margen noroeste de la Península Ibérica, se determina que las orientaciones obtenidas a partir del análisis de lineamientos extraídos del MDT del Margen Continental de Galicia y de las llanuras abisales adyacentes son un reflejo de los sistemas de fracturas que han controlado los rasgos morfoestructurales que definen este sector.Unidad de Tres Cantos, Instituto Geológico y Minero de España, EspañaDepartamento de Geología y Geoquímica, Universidad Autónoma de Madrid, Españ

The role of tectonic inheritance in the morphostructural evolution of the Galicia continental margin and adjacent abyssal plains from digital bathymetric model (DBM) analysis (NW Spain)

Acceso electrónico sólo desde el IGMEThe identification of recent major tectonic structures in the Galicia continental margin and adjacent abyssal plains was carried out by means of a quantitative analysis of the linear structures having bathymetric expression on the seabed. It was possible to identify about 5800 lineaments throughout the entire study area, of approximately 271,500 km2. Most lineaments are located in the Charcot and Coruña highs, in the western sector of the Galicia Bank, in the area of the Marginal Platforms and in the northern sector of the margin. Analysis of the lineament orientations shows a predominant NE–SW direction and three relative maximum directions: NW–SE, E–W and N–S. The total length of the lineaments identified is over 44,000 km, with a mode around 5000 m and an average length of about 7800 m. In light of different tectonic studies undertaken in the northwestern margin of the Iberian Peninsula, we establish that the lineaments obtained from analysis of the digital bathymetric model of the Galicia continental margin and adjacent abyssal plains would correspond to fracture systems. In general, the orientation of lineaments corresponds to main faults, tectonic structures following the directions of ancient faults that resulted from late stages of the Variscan orogeny and Mesozoic extension phases related to Triassic rifting and Upper Jurassic to Early Cretaceous opening of the North Atlantic Ocean. The N–S convergence between Eurasian and African plates since Palaeogene times until the Miocene, and NW–SE convergence from Neogene to present, reactivated the Variscan and Mesozoic fault systems and related physiography.Departamento de Geología y Geofísica, Instituto Geológico y Minero de España, EspañaDepartamento de Geología y Geoquímica, Universidad Autónoma de Madrid, Españ

Passive seismic methods: a cost-effective tool for subsurface characterization

[EN] Seismic methods are commonly usedfor subsurface imaging and geological characterization. Two different types of methods can be distinguished basedon the origin of the seismic waves that are analyzed.Active seismic methods study the propagation of artificially generated elastic waves using a controlled seismic source to obtain subsurface information.In the last years, there has been an increase interest in the use of passive seismic methods, mainly based on ambient noise analysis, for subsurface studies since they do not imply the use of any active sources, reducing the logistical complexity of the surveys.Peer reviewe

Guadalete river paleochannel characterization and evolution in the Bay of Cádiz during the late quaternary

Late Quaternary paleochannel and fluvial deposits characterization in the Bay of Cadiz have been carried out by geophysical, cores, and archeological data. They are located over alluvial deposits of regressive and lowstands systems tracts, and below the coastal deposits of transgressive systems tracts belong to the last depositional sequence. Paleochannels were generated during the sea level fall and lowstand position in the last glaciation stage, but fluvial sedimentary infill was produced after, as the sea level rose, during the transgression. Paleochannel and fluvial deposits have been also affected by several tectonic episodes which influence its position, internal structure and lateral movement, during and after its sedimentatio