Morphological and geological features of Drake Passage, Antarctica, from a new digital bathymetric model

The Drake Passage is an oceanic gateway of about 850 km width located between South America and the Antarctic Peninsula that connects the southeastern Pacific Ocean with the southwestern Atlantic Ocean. It is an important gateway for mantle flow, oceanographic water masses, and migrations of biota. This sector developed within the framework of the geodynamic evolution of the Scotia Arc, including continental fragmentation processes and oceanic crust creation, since the oblique divergence of the South American plate to the north and the Antarctic plate to the south started in the Eocene. As a consequence of its complex tectonic evolution and subsequent submarine processes, as sedimentary infill and erosion mainly controlled by bottom currents and active tectonics, this region shows a varied physiography. We present a detailed map of the bathymetry and geological setting of the Drake Passage that is mainly founded on a new compilation of precise multibeam bathymetric data obtained on 120 cruises between 1992 and 2015, resulting in a new Digital Bathymetric Model with 200 × 200 m cell spacing. The map covers an area of 1,465,000 km2 between parallels 52°S and 63°S and meridians 70°W and 50°W at scale 1:1,600,000 allowing the identification of the main seafloor features. In addition, the map includes useful geological information related to magnetism, seismicity and tectonics. This work constitutes an international cooperative effort and is part of the International Bathymetric Chart of the Southern Ocean project, under the Scientific Committee on Antarctic Research umbrella.This work was supported through projects CTM2014- 60451-C2-02/01, CTM2017-89711-C2-2/1-P and special action CTM2011-13970-E from “Ministerio de Ciencia, Innovación y Universidades” of Spain

Oceanographic and climatic consequences of the tectonic evolution of the southern scotia sea basins, Antarctica

The Scotia Sea is a complex geological area located in the Southern Ocean which evolution is closely linked to the opening of the Drake Passage. Structural highs of continental nature derived from the former continental bridge between South America and the Antarctic Peninsula surround the abyssal plains of the Scotia Sea, restricting small isolated sedimentary basins along its southern margin. Morpho-structural and seismo-stratigraphic analyses of multichannel seismic reflection profiles, and additional geophysical data available in the region, have been conducted, decoding regional and global implications of the basins' evolution. The main aim of this work is to describe the stratigraphic evolution of the southern Scotia Sea basins, from their opening in the back-arc tectonic context of the Scotia Sea, to the last oceanographic changes which have carried on global climatic implications. The evolution of the south Scotia Sea occurred through two major tectonic stages registered in the sedimentary record of the region: 1) the end of the subduction in the northwest part of the Weddell Sea during the early Miocene, which shortened the back-arc subduction trench generating a major change in the regional tectonic field that determined the evolution of the southern basins towards two different types of passive margins: magma-poor and magma-rich; and 2) the full development of the southern Scotia Sea basins during the middle Miocene, that led to the opening of deep oceanic gateways along the South Scotia Ridge. Interplay among tectonics, oceanography and climate is proposed to control the regional sedimentary stacking pattern, with coeval changes globally identified

Sedimentary thickness distribution in the Protector and Pirie basins (Scotia Sea, Antarctica): control factors

Se ha realizado un análisis de estratigrafía sísmica mediante perfiles sísmicos de reflexión multicanal en las cuencas de Protector y Pirie, las cuales están ubicadas en el en el Mar de Scotia meridional, en las proximidades del límite de placas Scotia-Antártica. Mediante este análisis se ha determinado la distribución de los deposcentros sedimentarios más importantes, lo que ha permitido comprobar que la distribución sedimentaria en dichas cuencas está controlada por la morfoestructura del basamento e influenciada por la distribución de las masas de agua profundas. Los resultados obtenidos permiten establecer que ambas cuencas constituyen un buen ejemplo de cuencas oceánicas profundas aisladas y desnutridas, sin aportes continentales y bajo la influencia de corrientes de fondo activas relacionadas con el Agua Profunda Circumpolar Antártica (CDW) y con el Agua Profunda procedente del Mar de Weddell (WSDW)The analysis of multichannel seismic profiles reveals that the distribution of sedimentary depocenters within the Protector and Pirie basins of the southern Scotia Sea, close to the Scotia-Antarctica plate boundary, is largely due to the morpho-structural control of the basement and influenced by the distribution of bottom currents. Both basins constituted a good example of small isolated and undernourished deep basins, lacking major continental inputs and under the influence of active bottom currents related to both the Antarctic Circumpolar deep Water and the Weddell Sea Deep Wate

Recent morpho-sedimentary processes in Dove Basin, southern Scotia Sea, Antarctica: A basin-scale case of interaction between bottom currents and mass movements

Multibeam bathymetric imagery and acoustic sub-bottom profiles are used to reveal distribution patterns of sub-surface sedimentation in Dove Basin (Scotia Sea). The goals of the study are to determine the imprint of the inflow of deep Antarctic water masses from the Weddell Sea into the Scotia Sea, to establish the factors driving the styles of contourite deposition and to discern the relative contribution of alongslope versus downslope processes to the construction of the uppermost late Quaternary sedimentary record in the basin. The most significant morpho-sedimentary features in Dove Basin are linked to contouritic processes and to mass movements. Plastered drifts on the flanks of the basin constitute the most common contouritic deposits. Basement-controlled drifts on top of structural elevations are common along the central ridge, the central basin plain and scattered along the basin flanks. Sheeted drifts occur on top of adjacent banks or are restricted to the deep basin. In contrast, mounded drifts are poorly represented in Dove basin. A laterally extensive contouritic channel runs along the central ridge. Contouritic channels are also identified in the upper parts of the lateral banks and slopes. Numerous slide scars along the upper parts of the slopes evolve downslope into semitransparent lens-shaped bodies, with occasional development of across-slope channels. Semitransparent lenses occur intercalated within stratified deposits in the slopes of the basin, in the central ridge and in the deepest basin plain. The spatial arrangement of contouritic morphologies points to the influence of the water column structure and the basin physiography. In the eastern sub-basin, two different fractions (lower and upper) of Weddell Sea Deep Water (WSDW) leave an imprint on contourite deposits owing to the sloping interface between the two fractions. Contouritic influence is more subdued in the western sub-basin, and limited to the imprint of the lower WSDW. The upper parts of the surrounding banks are under the influence of deep-reaching Circumpolar waters (i.e., Lower Circumpolar Deep Water), which develops both depositional and erosional morphologies. The cross-section V-shaped morphology of the basin and the common occurrence of structural highs drive the predominance of plastered and basement-controlled drifts in the sediment record. The frequent alternation between contourites and downslope gravity-flow deposits is likely due to different processes associated with over-steepening in the basin, such as basement-controlled steep slopes, deformed drifts atop basement elevations, and the development of thick contouritic piles. Dove Basin is an example of a basin without mounded, plastered or mixed hybrid drifts in the transition between the lower slope and the deep basin, because the upper boundary of the deepest water mass —the Weddell Sea Deep Water— flows shallower along the middle slope. This fact underlines the relevance of the position and depth of water masses in shaping the morphology of the feet of slopes along continental margins

New Magnetic Anomaly Map of the Antarctic

The second generation Antarctic magnetic anomaly compilation for the region south of 60 degrees S includes some 3.5 million line-km of aeromagnetic and marine magnetic data that more than doubles the initial map's near-surface database. For the new compilation, the magnetic data sets were corrected for the International Geomagnetic Reference Field, diurnal effects, and high-frequency errors and leveled, gridded, and stitched together. The new magnetic data further constrain the crustal architecture and geological evolution of the Antarctic Peninsula and the West Antarctic Rift System in West Antarctica, as well as Dronning Maud Land, the Gamburtsev Subglacial Mountains, the Prince Charles Mountains, Princess Elizabeth Land, and Wilkes Land in East Antarctica and the circumjacent oceanic margins. Overall, the magnetic anomaly compilation helps unify disparate regional geologic and geophysical studies by providing new constraints on major tectonic and magmatic processes that affected the Antarctic from Precambrian to Cenozoic times.Korea Polar Research Institute (KOPRI) programs, PM15040 and PE17050Germany's AWI/Helmholtz Center for Polar and Marine ResearchFederal Institute for Geosciences and Natural ResourcesBritish Antarctic Survey/Natural Environmental Research CouncilItalian Antarctic Research ProgrammeRussian Ministry of Natural ResourcesU.S. National Science Foundation and National Space and Aeronautics AdministrationAustralian Antarctic Division and Antarctic Climate & Ecosystem Cooperative Research CentreFrench Polar InstituteGlobal geomagnetic observatories network (INTERMAGNET

Onset and development of the Drake Passage and Scotia Sea gateways and its influence on global ocean circulation and climate (IODP proposal)

The DRAKE-SCOTIA SEA GATEWAYS is a new multidisciplinary International Ocean Discovery Program (IODP) drilling proposal aimed at determining the time of opening and pattern of development of gateways in the Drake Passage and the adjacent Scotia Sea, and their influence on global ocean circulation, biotic evolution and climate. The Drake Passage with the adjacent Scotia Sea represent one of Earth’s most important oceanic gateways, between the southern tip of South America and the Antarctic Peninsula, a crucial area for water mass exchange between the Pacific Ocean, the Atlantic Ocean and the Weddell Sea, the importance of which is evidence by in many multinational studies. Nevertheless, the region has not been yet drilled for scientific purposes. The objective of this work is to present the main scientific goals of this drilling proposal and its link with the IODP Science Plan for 2013-2023.Department of Earth Sciences, Royal Holloway University, Reino UnidoBritish Antarctic Survey, Reino UnidoDepartment og Geology and Geophysics, Yale University, Estados UnidosGeophysical Department, Geological Survey of Denmark and Greenland, DinamarcaAlfred Wegener Institute, Helmholtz for Polar and Marine Research, AlemaniaInstituto Geológico y Minero de España, EspañaOcean and Earth Science, University of Southampton, Reino UnidoUniversity Texas at Austin, Estados UnidosInstitute of Petroleum Engineering, Heriot-Watt University, Reino UnidoInstituto Andaluz de Ciencias de la Tierra, Consejo Superior de Investigaciones Científicas, EspañaInstituto Andaluz de Ciencias de la Tierra, Universidad de Granada, EspañaCollege of Earth, Ocean and the Environment, University of Delaware, Estados UnidosUniversity New South Wales, AustraliaUniversity Nebraska-Lincoln, Estados UnidosUniversidad de Buenos Aires, Argentin

Echo-character mapping of the Galician Continental Margin and the adjacent abyssal plains

La cartografía y análisis de las facies acústicas que se determinan a partir de la interpretación y correlación de los perfiles sísmicos de muy alta resolución, es una herramienta muy útil para la caracterización de los procesos sedimentarios recientes y su distribución en ambientes marinos profundos. Este trabajo presenta el primer mapa de ecocarácter del Margen Continental de Galicia y las llanuras abisales adyacentes. El mapa se realizó sobre la base del análisis e interpretación de los datos de batimetría y reflectividad de las ecosondas multihaz SIMRAD EM12, EM120 y EM1002, y los perfiles sísmicos de muy alta resolución de la ecosonda paramétrica SIMRAD TOPAS PS18. Sobre la base de la morfología del fondo marino, la reflectividad y los caracteres del eco acústico, se identificaron 26 tipos de ecos en la secuencia sedimentaria más superficial. Estos tipos de eco se han clasificado en cuatro grupos principales: bien definidos, irregulares, hiperbólicos y ondulados. Esta información ha sido adquirida en el marco del ‘Programa de Investigación Científica de la Zona Económica Exclusiva Española’, coordinado por el Ministerio de Defensa, durante las campañas oceanográficas que se han realizado a bordo del BIO Hespérides del 2001 a 2003 y del 2006 a 2009.The acoustic facies mapping and analyses from the interpretation and correlation of very high resolution seis- mic profiles, is a very useful tool for the characterization of the recent sedimentary processes and their distribution in the deep-sea environments. This work presents the first echo-character map of the Galicia Continental Margin and the adjacent abyssal plains. The map was carried out on the basis of the analysis and interpretation of the bathymetry and reflectivity data from the SIMRAD EM12, EM120 and EM1002 multibeam echosounders, and the high resolution seismic profiles from the SIMRAD TOPAS PS18 parametric echosounder. Based on the seafloor morphology, backscatter and acoustic echo-characters, 26 echo types were identified in the uppermost sedimentary sequence. These echo-types have been classified into four main groups: Distinct, Irregular, Hyperbolic and Undulated echoes. This information has been acquired in the framework of the ‘Scientific Research Program of the Economic Exclusive Zone of Spain’, which is coordinated by the Defense Ministry, during the oceanographic cruises carried out on board of the R/V Hesperides in 2001 to 2003 and 2006 to 2009.Depto. de Geodinámica, Estratigrafía y PaleontologíaFac. de Ciencias GeológicasTRUEMinisterio de Ciencia e Innovación (MICINN)Instituto Geológico y Minero de Españapu