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| Tallobre, Cedric; Loncke, Lies; Bassetti, Maria-angela; Giresse, Pierre; Bayon, Germain; Buscail, Roselyne; De Madron, Xavier Durrieu; Bourrin, Francois; Vanhaesebroucke, Marc; Sotin, Christine. |
| The Demerara Plateau, belonging to the passive transform margin of French Guiana, was investigated during the IGUANES cruise in 2013. The objectives of the cruise were to explore the poorly-known surficial sedimentary column overlying thick mass transport deposits as well as to understand the factors controlling recent sedimentation. The presence of numerous bedforms at the seafloor was observed thanks to newly acquired IGUANES bathymetric, high resolution seismic and chirp data, while sediment cores allowed the characterization of the deposits covering the mass transport deposits. Modern oceanographic conditions were determined in situ, using mooring monitoring over a 10-month period. Our data indicate the presence of a Contourite Depositional System... |
| Tipo: Text |
Palavras-chave: Marginal plateau; Contourite; Comet tail; Demerara Plateau. |
| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00308/41957/41220.pdf |
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| Fanget, Anne-sophie; Loncke, Lies; Pattier, France; Marsset, Tania; Roest, Walter; Tallobre, Cédric; Durrieu De Madron, Xavier; Hernandez Molina, F. Javier. |
| The Demerara Plateau, off the French Guiana and Surinam margin, corresponds to a prominent sub-horizontal marginal plateau. The interpretation of a large set of seismic data acquired along the Demerara Plateau and integration with previous seismic stratigraphy and drill studies enables a better understanding of the sedimentary evolution of the outer Demerara marginal plateau. Since the end of the transform activity (late Albian), three sedimentary evolutionary stages have been identified. 1) The Pre-contourite Stage (late Albian to early Miocene) is strongly controlled by the structure of the margin that influences the distribution pattern of post-transform deposits through differential thermal subsidence between transform and divergent segments. 2) The... |
| Tipo: Text |
Palavras-chave: Marginal plateau; Demerara Plateau; Contourite; Bottom currents; Mass transport deposits; Atlantic Ocean. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00599/71125/69439.pdf |
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| Giresse, Pierre; Bayon, Germain; Tallobre, Cédric; Loncke, Lies. |
| Contourite sediment accumulations at continental margins are related to strong bottom water circulation, where intense winnowing can result in neoformation of authigenic grains of glauconite at the seafloor. In this study, we investigated whether such glauconite grains could faithfully record ambient bottom-water neodymium (Nd) isotopic compositions, and hence be used as paleoceanographic archives. To this purpose, we measured Nd isotopic compositions (εNd) in a series of glauconitic grains, foraminiferal assemblages, leached Fe-Mn oxyhydroxide phases, and detrital clays separated from a contourite sediment record at the Demerara slope off French Guiana (IG-KSF-11; 2370 m water depth), at a location where the present-day εNd distribution along the water... |
| Tipo: Text |
Palavras-chave: Rare earth elements; Neodymium isotopes; Glauconitisation; Demerara; Contourite. |
| Ano: 2021 |
URL: https://archimer.ifremer.fr/doc/00689/80085/83115.pdf |
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| Tallobre, Cédric; Giresse, Pierre; Bassetti, Maria-angela; Loncke, Lies; Bayon, Germain; Buscail, Roselyne; Tudryn, Alina; Zaragosi, Sébastien. |
| The Demerara Plateau is a marginal plateau which forms a bathymetric relief on the sea floor. Here, contourite deposits have been studied in detail, following the recent discovery of contourite sequences likely related to the bottom currents and linked both to contour current and peculiar sea-floor morphology. A chronostratigraphic framework, based on δ18O relative variations and palaeomagnetic events in sediment cores allows correlating sediment processes to current intensity changes and major climate phases (glacial or interglacial). The studied sediments are enriched in glauconitic grains. In addition, the glauconite mineralogical maturity can easily correlate to low sedimentation rate and slightly energetic bottom currents on the seafloor. Based on... |
| Tipo: Text |
Palavras-chave: Marginal plateau; Contourite; Glauconite; Demerara plateau. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00485/59665/62724.pdf |
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| Mercier De Lepinay, Marion; Loncke, Lies; Basile, Christophe; Roest, Walter; Patriat, Martin; Maillard, Agnes; De Clarens, Philippe. |
| We present a global inventory of transform continental margins, based on both a worldwide comparison of continent-ocean boundary identifications with oceanic fracture zones traces, and a compilation of published regional studies. This inventory increases the number of identified transform margins from 29 to 78. These margins represent 16% of continental margins in cumulative length and 31% of non-convergent margins. We include morphological data, published upper crustal sections, continent to ocean transition locations and published Moho shape data in the new database. This review confirms that continent to ocean transitions are sharper at transform margins than at divergent margins. It also emphasizes the structural diversity of transform margins.... |
| Tipo: Text |
Palavras-chave: Transform margin; Continental margin physiography; Marginal ridge; Marginal plateau. |
| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00343/45372/44868.pdf |
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| Basile, Christophe; Girault, Igor; Paquette, Jean-louis; Agranier, Arnaud; Loncke, Lies; Heuret, Arnauld; Poetisi, Ewald. |
| We report the discovery of 173.4 Ma hotspot-related magmatic rocks in the basement of the Demerara Plateau, offshore French Guiana and Suriname. According to plate reconstructions, a single hotspot may be responsible for the magmatic formation of (1) both the Demerara Plateau (between 180 and 170 Ma) and the Guinea Plateau (circa 165 Ma) during the end of the Jurassic rifting of the Central Atlantic; (2) both Sierra Leone and Ceara Rises (mainly from 76 to 68 Ma) during the upper Cretaceous oceanic spreading of the Equatorial Atlantic ocean; (3) the Bathymetrists seamount chain since the upper Cretaceous. The present-day location of the inferred Sierra Leone hotspot should be 100 km west of the Knipovich Seamount. |
| Tipo: Text |
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| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00628/74034/73363.pdf |
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| Marsac, Francis; Galletti, Florence; Ternon, Jean-francois; Romanov, Evgeny V.; Demarcq, Herve; Corbari, Laure; Bouchet, Philippe; Roest, Walter; Jorry, Stephan; Olu, Karine; Loncke, Lies; Roberts, Michael J.; Ménard, Frédéric. |
| There is a growing interest in the management of seamounts of the South Western Indian Ocean (SWIO) both in waters under national jurisdictions and in the Areas Beyond National Jurisdiction (ABNJ). On the one hand, new scientific knowledge has been gathered through various oceanographic cruises during the past decade and, on the other hand, new agreements are under consideration globally to promote conservation and sustainable use of the biodiversity in the ABNJ, where the deep sea ecosystems associated to seamounts are a growing matter of concern. SWIO seamounts have attracted interests from fishing operators since the 1960s, while mining exploration contracts have been recently granted. Seamounts are known to shelter rich, fragile and poorly resilient... |
| Tipo: Text |
Palavras-chave: International Law of the Sea; Vulnerable Marine Ecosystems; Deep-sea fisheries; Deep-sea mining; Benthic biodiversity; Saya de Malha Bank; South Indian Ocean Fisheries Agreement; Areas Beyond National Jurisdiction; Amended Nairobi Convention; Marine protected areas. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00598/71049/69362.pdf |
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