Structure and evolution of the Demerara Plateau, offshore French Guiana : rifting, tectonic inversion and post-rift tilting at transform-divergent margins intersection

International audienceWe present the structure and evolution of the eastern part of the Demerara plateau, offshore French Guiana, from the analysis of geophysical data collected during GUYAPLAC cruise. This area is located at the intersection of a transform segment and a divergent segment of a continental margin related to the Early Cretaceous opening of the Equatorial Atlantic. The main structures are NNE-SSW to NNW-SSE trending normal faults on the eastern edge of the plateau, and WNW-ESE to NW-SE trending acoustic basement ridges on its northern edge. When replaced in their Albian position, these structures appear to be parallel to the coeval oceanic accretion axis and transform faults, respectively. The most striking structures are related to a post-rift but syn-transform tectonic inversion, producing E-W to WNW-ESE trending folds, sealed by a regional unconformity. This shortening can not be related to ridge push, but is probably related to a plate kinematic change 105 My ago, that modified the deformation in the vicinity of the transform fault. Late post-rift evolution also includes a significant Tertiary oceanward tilt of the edge of the Demerara plateau. The driving mechanism of this late tilt is unclear, but may be related to a lithospheric flexure resulting from the loading of the abyssal plain by the Orinoco and Amazon deep-sea fans

Building of the Amsterdam-Saint Paul plateau: A 10 Myr history of a ridge-hot spot interaction and variations in the strength of the hot spot source

International audienceThe Amsterdam-Saint Paul plateau results from a 10 Myr interaction between the South East Indian Ridge and the Amsterdam-Saint Paul hot spot. During this period of time, the structure of the plateau changed as a consequence of changes in both the ridge-hot spot relative distance and in the strength of the hot spot source. The joint analysis of gravity-derived crust thickness and bathymetry reveals that the plateau started to form at ~10 Ma by an increase of the crustal production at the ridge axis, due to the nearby hot spot. This phase, which lasted 3-4 Myr, corresponds to a period of a strong hot spot source, maybe due to a high temperature or material flux, and decreasing ridge-hot spot distance. A second phase, between ~6 and ~3 Ma, corresponds to a decrease in the ridge crustal production. During this period, the hot spot center was close to the ridge axis and this reduced magmatic activity suggests a weak hot spot source. At ~3 Ma, the ridge was located approximately above the hot spot center. An increase in the hot spot source strength then resulted in the building of the shallower part of the plateau. The variations of the melt production at the ridge axis through time resulted in variations in crustal thickness but also in changes in the ridge morphology. The two periods of increased melt production correspond to smooth ridge morphology, characterized by axial highs, while the intermediate period corresponds to a rougher, rift-valley morphology. These variations reveal changes in axial thermal structure due to higher melting production rates and temperatures

Platelets of patients with chronic kidney disease demonstrate deficient platelet reactivity in vitro

<p>Abstract</p> <p>Background</p> <p>In patients with chronic kidney disease studies focusing on platelet function and properties often are non-conclusive whereas only few studies use functional platelet tests. In this study we evaluated a recently developed functional flow cytometry based assay for the analysis of platelet function in chronic kidney disease.</p> <p>Methods</p> <p>Platelet reactivity was measured using flow cytometric analysis. Platelets in whole blood were triggered with different concentrations of agonists (TRAP, ADP, CRP). Platelet activation was quantified with staining for P-selectin, measuring the mean fluorescence intensity. Area under the curve and the concentration of half-maximal response were determined.</p> <p>Results</p> <p>We studied 23 patients with chronic kidney disease (9 patients with cardiorenal failure and 14 patients with end stage renal disease) and 19 healthy controls. Expression of P-selectin on the platelet surface measured as mean fluorescence intensity was significantly less in chronic kidney disease patients compared to controls after maximal stimulation with TRAP (9.7 (7.9-10.8) vs. 11.4 (9.2-12.2), P = 0.032), ADP (1.6 (1.2-2.1) vs. 2.6 (1.9-3.5), P = 0.002) and CRP (9.2 (8.5-10.8) vs. 11.5 (9.5-12.9), P = 0.004). Also the area under the curve was significantly different. There was no significant difference in half-maximal response between both groups.</p> <p>Conclusion</p> <p>In this study we found that patients with chronic kidney disease show reduced platelet reactivity in response of ADP, TRAP and CRP compared to controls. These results contribute to our understanding of the aberrant platelet function observed in patients with chronic kidney disease and emphasize the significance of using functional whole blood platelet activation assays.</p

Erratum to: 36th International Symposium on Intensive Care and Emergency Medicine

[This corrects the article DOI: 10.1186/s13054-016-1208-6.]

EXTRAPLAC : les enjeux, pour la France, de son plateau continental

The UN’s Law of the Sea Convention, adopted in 1982 and ratified by France in 1996, attributes sovereign rights to nation-states over an exclusive economic zones extending from the coasts out to 200 nautical miles (approximately 370 km). Under article 76 of the Convention, a state may claim an extension of this zone to 350 nautical miles (or even farther under certain conditions) if the continental shelf stretches beyond the 200-limit. It is, of course, necessary to prove that this condition holds. For this purpose, France launched, in 2002, a national program, EXTRAPLAC, for assembling the scientific and technical evidence that demonstrates the validity of such an extension from the coasts of the country and its overseas departments and territories. This program will submit the evidence to, and even defend it before, the UN Commission on the Limits of the Continental Shelf. Through this program, France is addressing important questions about extending its continental shelf, among them : the access to natural resources, protection of the environment, scientific research and the country’s geopolitical strategy. Despite the legal and its diplomatic context, EXTRAPLAC is still, first and foremost, a scientific program.La Convention des Nations Unies sur le droit de la mer, adoptée en 1982 et ratifiée par la France en 1996, attribue aux États côtiers des droits souverains s’étendant en mer jusqu’à 200 milles nautiques (M) des côtes (environ 370 km), c’est la Zone économique exclusive. L’article 76 de la Convention stipule que si le prolongement naturel du territoire terrestre d’un État s’étend au-delà de cette limite, ledit État peut revendiquer une extension de son plateau continental jusqu’à 350 M, voire au-delà dans certaines conditions. Mais encore faut-il être en mesure de prouver que le plateau continental s’étend aussi loin. Pour cela, la France a mis en place, en 2002, le programme national EXTRAPLAC (EXTension RAisonnée du PLAteau Continental), qui est chargé de constituer les dossiers scientifiques et techniques démontrant cette extension au large des territoires de la métropole et des collectivités de l’Outre-mer, et de les soutenir voire de les défendre devant la Commission des limites du plateau continental, auprès de l’ONU (à New York). À travers ce programme, la France répond aux importants enjeux de l’extension de son plateau continental, dont, entre autres, l’accès aux ressources naturelles, la protection de l’environnement, la recherche scientifique et la stratégie géopolitique. Bien que s’inscrivant dans un contexte juridique et diplomatique, la démarche du programme EXTRAPLAC reste avant tout scientifique.La Convención de las Naciones Unidas sobre el Derecho del Mar, adoptada en 1982 y ratificada por Francia en 1996, atribuye a los Estados costeros derechos soberanos sobre el mar hasta 200 millas náuticas (M) de las costas (unos 370 km) ; es lo que se conoce como zona económica exclusiva. El artículo 76 de la Convención estipula que, si la prolongación natural del territorio terrestre de un Estado va más allá de este límite, dicho Estado podrá reclamar una extensión de su zona económica exclusiva hasta 350 M, o incluso más allá en determinadas condiciones. Pero para ello, hay que demostrar que la plataforma continental se extiende hasta dicho punto. Por esta razón, Francia ha puesto en marcha, en 2002, el programa nacional EXTRAPLAC (EXTensión RAzonada de la PLAtaforma Continental), que se encarga de conformar, apoyarlo e incluso defender ante la Comisión de Límites de la plataforma continental de las Naciones Unidas (Nueva York) los expedientes técnicos y científicos que demuestren esta extensión sobre el mar de los territorios costeros continentales y de las regiones de ultramar. A través de este programa, Francia responde a los importantes retos de la extensión de su plataforma continental, entre otras cosas, el acceso a los recursos naturales, la protección del medioambiente, la investigación científica y la estrategia geopolítica. Aunque se inscriba en un marco jurídico y diplomático, el enfoque del programa EXTRAPLAC es ante todo científico

Combining Law of the Sea Continental Shelf Delineation and Scientific Interests: The Case of the Demerara Plateau Offshore French Guiana and Surinam

As an international scholar visiting CCOM for two months at the invitation of Larry Mayer, I would like to use this seminar as an opportunity to present a brief description of my career path and my research and related professional activities. This will allow staff and students to know more about my background and research themes. I encourage all of you to come and visit me in my office at CCOM for exchanges, because these are the whole point of my stay at UNH; my door is always open. Follows a presentation of the French UNCLOS program EXTRAPLAC. During this program some 20 mapping cruises were carried out offshore the French mainland and its overseas territories to characterize the seabed and subsoil. We tried as much as possible to combine scientific interest in these regions, often poorly mapped and understood, with scientific research involving Master and Ph.D. students. In particular, I will discuss the example of the Demerara Plateau, offshore French Guiana and Surinam, where the initial EXTRAPLAC cruise of 2003 has led to academic collaboration and three follow-up cruises, with a fourth cruise planned for 2023. I will conclude by stressing the opportunities for seafloor mapping that UNCLOS has provided, and by expressing some concern on the slow progress made by the Commission on the Limits of the Continental Shelf that has to examine the ECS submissions of coastal States. Presenter Bio Walter Roest obtained a Ph.D. in marine geophysics from the University of Utrecht in the Netherlands. After a 3-year post doc at the Atlantic Geoscience Center (Bedford Institute in Dartmouth, Nova Scotia, Canada), he worked at the Geological Survey of Canada (GSC), in Ottawa, Ontario, primarily on continental magnetic and gravity acquisition and interpretation. Over the years, he also occupied several management positions at the GSC. In 2003, Walter was appointed director of the Marine Geosciences Department of Ifremer, the French Public Institute for Marine Research, in Brest, France. He led the French program for the extended continental shelf (ECS) in the framework of the UN Convention on the Law of the Sea from 2003 to 2012, including many mapping cruises offshore the French overseas territories. He served as a member and one of the vice-presidents of the UN Commission on the Limits of the Continental Shelf from 2012 to 2017. His research interests are in plate tectonics, fracture zones, the evolution of continental margins. He also participated actively in the development of several large-scale open access geophysical data compilations. Walter Roest’s stay at CCOM is sparked by his interest in seafloor mapping, Seabed2030, the Map the Gaps initiative, the GEBCO/Nippon training program, as well as the ECS work in which CCOM is involved. His current research interests include: The formation and evolution of continental margins, and in particular transform margins and associated transform margin plateaus, such as the Demerara Plateau offshore French Guiana and Surinam. Issues related to ECS, including the interpretation of the Convention and application of the relevant provisions of its Article 76. Hazards related to the large double transform fault system in the region of Haiti. He obtained the funding from the French National Fleet for a multidisciplinary research cruise, to be programmed in 2024 or 2025 (seafloor mapping, active and passive seismics and coring combined with onshore paleo seismology work)

I-4. Quels potentiels supplémentaires apporterait une extension du plateau continental juridique ?

1. La ZEE française – Potentiel de l’outre-mer 1.1 Introduction Avec onze millions de kilomètres carrés de Zone Economique Exclusive, la France dispose du deuxième espace maritime mondial, après celui des États-Unis. Cet immense espace maritime, réparti dans tous les océans dote la France d’un potentiel d’une grande richesse en matière du potentiel de ressources dont l'inventaire reste, pour l'essentiel, à réaliser. Ce potentiel porte principalement sur les ressources minérales et la biodiver..

Challenges and Opportunities for the CLCS: Insight from the Insiders

The Commission on the Limits of the Continental Shelf (CLCS) is one of the bodies established under the United Nations Convention on the Law of the Sea (UNCLOS) to evaluate submissions made by coastal States who have ratified UNCLOS as to the limits of their continental shelves beyond 200 M. These limits define the sovereign rights of those States for the exploration and exploitation of natural resources at and below the seafloor, and the limits are defined according to criteria specified in UNCLOS. The CLCS consists of 21 members appointed for a term of 5 years according to a regional allocation, who are experts nominated by States Parties to UNCLOS in the fields of geology, geophysics and hydrography to evaluate these submissions. Three submissions have traditionally been evaluated at any one time by individual subcommissions with 7 members each. The first CLCS was appointed in 1997 and in the subsequent 15 years the Commission has approved 18 of the over 100 submissions that are anticipated. In 2008, the States Parties to UNCLOS made recommendations concerning the operation of the CLCS designed to improve the rapidity of the process. In 2012, 12 new members were elected, while 9 former members were re-elected, to the CLCS and their residency in New York was at least doubled from previous practice to a minimum of 21 weeks per year. Subsequently, it was decided to triple the number of simultaneously working subcommissions to a total of 9, so that each member is now working on three different submissions. Further changes may increase the efficiency and efficacy of the Commission. Three new members from the Western European and Others Group (WEOGs!) are here to share their thoughts about the current operation of, and potential improvements in, the modus operandi of CLCS. Presenter Bio Walter R. Roest has a PhD in marine geophysics from the VeningMeineszLaboratory of the University of Utrecht, the Netherlands. After a 3 year Post-doc at the Atlantic Geoscience Centre of the Bedford Institute of Oceanography in Nova Scotia, Canada, he joined the Geological Survey of Canada in Ottawa and worked mainly in potential field acquisition, processing, compilation and interpretation. During that period, he headed the Crustal Geophysics Subdivision, was acting Chief Geoscientist, and acting director of the Continental Geosciences Division of the GSC, before joining the French marine research institute Ifremer in Brest in 2003, as director of the Marine Geosciences Department. From 2004 to 2013, he headed the French UNCLOS program for the extension of the continental shelf, and led many research cruises off the French overseas territories. He is (co-) author of over 70 peer reviewed papers, dealing with topics ranging from global geodynamics, regional magnetics and tectonics to detailed magnetic interpretation methodology for exploration purposes. Despite his Dutch citizenship, Walter Roest was nominated by France to be a member of the Commission on the limits of the continental shelf, and elected in 2012. Martin V. Heinesen has a Cand.Scient. degree in Geology from Copenhagen University, Denmark (1987). He has ever since worked for the Government of the Faroe Islands – as the head of the Geological Department at the Museum of Natural History (1987-2000); director of the Faroese Petroleum Administration (1993-97); director of the Faroese Geological Survey (2000-03); and since 2003 as the project manager of the Continental Shelf Project of the Kingdom of Denmark, with respect to the Faroe Islands. He is an external lecturer in Geology at the University of the Faroe Islands, and he is member of the Delegation of the Kingdom of Denmark in charge of continental shelf delimitation negotiations between the Faroe Islands and neighboring coastal States, within and beyond 200 M. In 2012 he was elected as member of the Commission on the Limits of the Continental Shelf, nominated by Denmark together with the other Nordic countries. Richard Haworth has an Honours Degree in Physics (with Geology and Mathematics) from Durham University, U.K. and a Ph.D. in Marine Geophysics from the University of Cambridge. Much of his Ph.D. research work was carried out on Canadian research vessels, which is why in 1968 he emigrated to Canada. He spent 15 years as a marine geophysical research scientist working out of the Bedford Institute of Oceanography in Nova Scotia before he thought he needed to seek wider horizons. That took him to the British Geological Survey for 7 years as Chief Geophysicist, before returning home to Canada in 1990. He was a Director General of the Geological Survey of Canada from 1990 until June 2000 when he was appointed Assistant Deputy Minister with Natural Resources Canada. He retired from the public service in 2003, returning to Nova Scotia where as an Adjunct Professor at Dalhousie University he taught Environmental Policy for 6 years before he returned to his previous work on the Law of the Sea by preparing one Submission to the Commission on the Limits of the Continental Shelf and the editing another. In 2012, he was elected to the Commission

Age of the Ocean Floor: A Digital Data Set for the Labrador Sea and Western North Atlantic

A digital grid of ocean floor ages was constructed from a combination of magnetic anomaly identifications and recent plate kinematic models of the North Atlantic and Labrador Sea. Comparing large gridded geophysical data sets with these gridded age values is a powerful means of studying the variation of geophysical parameters with lithospheric age, and the dynamic processes in the Earth. The data set from the western North Atlantic and Labrador Sea shows the dependence on age of bathymetry, depth-to-basement and gravity