ALBERT

Description: Summary The Bathymetrists Seamounts (BSM) are located north of the volcanic Sierra Leone Rise in the eastern Atlantic between 6° and 9°N. The three W-E, N-S and NE-SW striking directions of the seamounts indicate a clear structural control for the emplacement of these volcanoes. The origin of the melts, their relationship to the Sierra Leone Rise and the role of the faults in the formation of the melts are unknown as the BSM could be explained by plume related volcanism or decompression melting beneath deep (transform) faults. The SEDIS-cruise M152/2 of RV METEOR strove for a better understanding of the life cycle of submarine volcanoes and their effect on the oceanic lithosphere in the oceanic intraplate setting of the BSM and the relationship to the Sierra Leone Rise. The aims were: 1) to understand the interaction between crustal thickness, tectonics and volcanic phases, 2) to investigate the structural, chronological and petrological evolution of individual seamounts and seamount chains, 3) to review slope failures and resulting mass flow processes. We addressed these objectives by more than 4000 km highresolution reflection seismic and more than 5000 km of parametric echosounder, multi-beam, and gravity and magnetic profiles. Rock samples for ground truthing and geochemical research have been collected during 14 dredge stations. We further determined the concentrations in surface seawater and air and the state of air-sea exchange of a number of nowadays globally banned pesticides, polychlorinated biphenyls, brominated flame retardants, polycyclic aromatic hydrocarbons and their derivatives. Zusammenfassung Die Bathymetrists Seeberge liegen nördlich der Sierra Leone Schwelle, einer vulkanischen Plattform im östlichen Atlantik zwischen 6° und 9° N. Diese submarinen Vulkane gruppieren sich entlang W-E, N-S und NE-SW Trends, was eine strukturelle Kontrolle der Vulkanentstehung indiziert. Die Schmelzentstehung sind unbekannt und können mit PlumeVulkanismus oder Dekompressionsschmelzen unter bisher nicht untersuchten Störungen und tiefen Transformstörungen zusammenhängen. Der Bezug zur Sierra Leone Schwelle ist ebenfalls unbekannt. Im Zuge der SEDIS-Expedition M152/2 mit FS METEOR wurde der Lebenszyklus von Unterwasservulkanen und deren geochemischen Einfluss auf die ozeanische Lithosphäre der Bathymetrists Seeberge untersucht. Anhand der profilhaften geophysikalischer Messungen und Dredge-Proben wollen wir 1) die Wechselwirkung zwischen Krustenmächtigkeit, Tektonik und Vulkanismus verstehen, 2) die strukturelle, chronologische und petrologische Entwicklung von Vulkanen und Vulkanketten untersuchen, und 3) Auslösemechanismen, Transportprozesse und Volumina von Hangrutschungen studieren. Zur Bearbeitung der wissenschaftlichen Fragen sammelten wir mehr als 4000 km mehrkanal-reflexionsseismischer und mehr als 5000 km parametrische Sedimentecholot, Fächerlot, Schwere und Magnetik-Profile. Für die geochemischen Arbeiten sammelten wir an 14 Stationen Gesteinsproben unter Einsatz einer Dredge. Die regelmäßige Beprobung der Luft und des Oberflächenwassers diente der Bestimmung der Konzentration von heute weltweit verbotenen Pestiziden, polychlorierten Biphenylen, bromierten Flammschutzmitteln, polyzyklischen aromatischen Kohlenwasserstoffen und deren Derivaten und um den Austausch zwischen Luft und Meer weiter zu verstehen.

Description: Despite over 100 years of acoustic seabed mapping, only around 15% of the seafloor has ever been directly mapped and little of the mapping performed has been systematic or over larger areas. The result is that our knowledge of seafloor structure is rudimentary and our understanding of the processes which form them has, in principle, advanced little since the advent of plate tectonics. Societally, the seafloor plays a vital role in humanity’s "life support system", for example providing habitat for marine organisms, stimulating mixing of ocean water as part of the overturning circulation system and increasingly being the site of industrial installations. It is scientifically and societally imperative that we bring the level of knowledge of the surface of our planet up to that of bodies like Moon and Mars that are mapped with a resolution better than 100 m per pixel. It is also essential that the data are made freely available to all to support research and conservation. The aim of this cruise was to map previously uncharted part of the tropical Atlantic using the ship’s multibeam system and to provide the data to global open databases as well as to acquire magnetic gradient data along the same tracks. Magnetic anomalies from so-called Oceanic Core Complexes challenged the conventional view that marine magnetic anomalies arose in the upper, extrusive layer of the oceanic crust, because the crust has been stripped away at these complexes. We therefore collected magnetic data simultaneously to the multibeam data in order to constrain the interpretation of the observed seabed morphology.

Description: The origin of broad intraplate volcanic provinces has been related to deep mantle plumes or shallow lithospheric processes, e.g., underlying large fault systems. One example of an understudied intraplate volcanic province is the Bathymetrists Seamounts (BSM) in the central-eastern Atlantic, an area with dense and extended fracture zones, but the BSM has been associated with a mantle plume origin. Extensive bathymetric mapping and seafloor sampling show that most BSM-seamounts resemble flat-topped guyots capped by carbonate platforms. Vesicular, volcanoclastic samples imply that their tops formed near sea level, followed by reef formation during cessation of volcanism and crustal subsidence. Erosion determines the seamount irregularity proportional to their sizes. Strong ellipticity of some seamounts is related to multiple vents that erupted along fractures. The orientation of the volcanoes, carbonate platforms, and morphological lineaments of the BSM show particular trends that reveal information on their origin and formation mechanisms. Geomorphological analyses indicate a structural control on volcano emplacement related to underlying lithospheric faults resembling a Riedel shear pattern. The stress field corresponding to their orientations is related to a NE-SW tensional setting, fitting to the prevalent tectonic setting ~56–38 Ma years ago that coincides with the BSM formation and an increase in spreading rates. A change in movement of the African plate during this time, together with the reactivation of fracture zones of the strongly sheared equatorial Atlantic, created pathways in the lithosphere and possibly enhanced magmatism. The seamounts do not show distinct differences in erosion state, morphology, carbonate platform depth, or Mn-crust thickness, in contrast to what would be expected for an age progression within the seamount chain. Our observations, therefore, do not support a plume mantle source. While the magmatic source remains undefined, we show that tectonic pathways determined the shape of the seamounts and enabled the broad emplacement of the Bathymetrists seamount chain.

Description: Gridded multibeam bathymetry from Pelagia cruise 64PE445, Project SALTAX in 2018. The raw-data were post-processed and gridded at a resolution of 30 m with QPS Qimera. Small gaps are interpolated. TFW and PRJ files included. For RAW data please contact the authors.

Description: The multibeam raw data has been cleaned, quality assured and processed using QPS Qimera. Data products include ungridded soundings, bathymetric grids (150 m resolution) and an area shapefile. The data processing and provision took place within the EU Horizon 2020 project AtlantOS - Optimising and Enhancing the Integrated Atlantic Ocean Observing Systems. For map of transit track see: https://doi.org/10.1594/PANGAEA.883146

Description: The multibeam raw data has been cleaned, quality assured and processed using QPS Qimera. Data products include ungridded soundings and bathymetric grids (150 m resolution). The data processing and provision took place within the EU Horizon 2020 project AtlantOS - Optimising and Enhancing the Integrated Atlantic Ocean Observing Systems. For map of transit track see: https://doi.org/10.1594/PANGAEA.869762

Description: The multibeam raw data has been cleaned, quality assured and processed using QPS Qimera. Data products include ungridded soundings, a bathymetric grid (150 m resolution) and an area shapefile. The data processing and provision took place within the EU Horizon 2020 project AtlantOS - Optimising and Enhancing the Integrated Atlantic Ocean Observing Systems. For map of transit track see: https://doi.org/10.1594/PANGAEA.903617

Description: The multibeam raw data has been cleaned, quality assured and processed using QPS Qimera. Data products include ungridded soundings, bathymetric grids (150 m resolution), an area shapefile, a backscatter image (100 m resolution) as well as the ship track. The data processing and provision took place within the EU Horizon 2020 project AtlantOS - Optimising and Enhancing the Integrated Atlantic Ocean Observing Systems. For map of transit track see doi:10.1594/PANGAEA.864817

Description: The multibeam raw data has been cleaned, quality assured and processed using QPS Qimera. Data products include ungridded soundings and a bathymetric grid (150 m resolution). The data processing and provision took place within the EU Horizon 2020 project AtlantOS - Optimising and Enhancing the Integrated Atlantic Ocean Observing Systems. For map of transit track see: https://doi.org/10.1594/PANGAEA.897106

Description: The multibeam raw data has been cleaned, quality assured and processed using QPS Qimera. Data products include ungridded soundings, a bathymetric grid (150 m resolution) and an area shapefile. The data processing and provision took place within the EU Horizon 2020 project AtlantOS - Optimising and Enhancing the Integrated Atlantic Ocean Observing Systems. For map of transit track see: https://doi.org/10.1594/PANGAEA.881314