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Last name: AUGUSTIN
First name: Adolpho
International audience
The Nile deep-sea fan is the largest Plio-Quaternary depocentre in the Mediterranean Sea, extending over an area of >150,000 km2 within which rapid deposition drives syn-sedimentary collapse tectonics, as well as widespread seafloor venting of mixed thermogenic and biogenic gases. It is thus an ideal setting for the near-seabed accumulation of...
This chapter starts with an introduction of the topic of natural gas hydrates, presenting the main existing types, how they form, the main gases involved in their formation, their economic and environmental (including climate change and as geohazards) importance, in addition to their worldwide natural occurrences. Also included is a brief...
Gas hydrate provinces occur in two sedimentary basins along Brazil's continental margin: (1) The Rio Grande Cone in the southeast, and (2) the Amazon deep-sea fan in the equatorial region. The occurrence of gas hydrates in these depocenters was first detected geophysically and has recently been proven by seafloor sampling of gas vents, detected...
The Nile deep-sea fan is rich in fluid vents, including a Central Province of acoustically reflective patches that correspond at seafloor to fractured carbonate pavements hosting chemosynthetic ecosystems. The backscatter patches (BPs) have been referred to as pockmarks, but several studies have noted positive relief. We examine the BPs by...
Submarine gas hydrate systems are increasingly recognised to be associated with seafloor features recording the venting of gas-rich fluids to the deep ocean. The Amazon deep-sea fan contains a gas hydrate system characterised by a discontinuous bottom simulating reflection (BSR) forming elongate patches that follow the crests of thrust-folds...
Ocean warming related to climate change has been proposed to cause the dissociation of gas hydrate deposits and methane leakage on the seafloor. This process occurs in places where the edge of the gas hydrate stability zone in sediments meets the overlying warmer oceans in upper slope settings. Here we present new evidence based on the analysis...
The Brazilian continental margin contains natural gas hydrate (NGH) provinces known from bottom simulating reflections (BSRs). In the Amazon deep-sea fan, a BSR is recognised on the upper slope (700-2250 m depths), within a thrust-fold belt linked to gravitational collapse of the up to 10 km thick depocenter above detachment surfaces. Recurrent...
The submarine fans of large rivers are important sites of long-term carbon storage, but are also settings in which the rapid deposition of organic-rich sediment drives linked processes of gas and gas hydrate formation, fluid expulsion, mass failure and gravity tectonism. The Ama- zon River culminates in one of the world's largest deep-sea fans,...
The existence of gas hydrate systems along Brazil's vast continental margin has been known since the 1980s, based on observations of bottom simulating reflectors (BSRs) in two large shelf-slope depocenters: (1) the Amazon deep-sea fan in the Foz do Amazonas Basin and (2) Rio Grande Cone in Pelotas Basin. These depocenters are both undergoing...
Deep-sea fans have been proposed to act as carbon sinks, rapid deposition driving shallow methanogenesis to favor net storage within the gas hydrate stability zone (GHSZ). Here, we present new evidence of widespread gas venting from the GHSZ on the upper Amazon deep-sea fan, together with analyses of the first samples of gas hydrates recovered...
Fluid migration strongly influences gas hydrate occurrences, increasing concentrations in proportion to gas supply. An upward flow of gas-rich fluids is also central to models proposed to account for the formation of venting features within the gas hydrate stability zone (GHSZ), and for the presence or absence at its based of bottom simulating...
La campagne SEAGAL est demandée sur la marge nilotique à bord du NO Marion Dufresne par l'UMR Géoazur en collaboration avec des partenaires français (Universités de Nice Sophia Antipolis, UPMC et Université Bordeaux1, Ifremer), Brésiliens (PUCRS-IPR), Allemands (Jacobs University Bremen), Italiens (OGS) et Egyptiens (Université d'Alexandrie)....