KETZER , Marcelo

Large deep-sea fans are useful settings to study gas hydrate systems, the rapid burial of organic-rich sediment driving linked processes of gas generation, fluid expulsion and syn-sedimentary tectonism. The Nile deep-sea fan (100,000 km2) is a collapsing Late Cenozoic depocentre that is both a hydrocarbon province and an area of widespread...

The equatorial Atlantic margin to the north of the Amazon is strongly affected by gravi- tational processes presenting all forms of rupture of submarine slopes, representing a major geological hazard. The potential causal factors of these underwater landslides were studied from the integration of marine geophysical data (sediment sounder) and...

The Amazon deep sea fan is a dynamic setting in which widespread seafloor fluid vents record degassing of a gas hydrate system hosted within an upper slope thrust-fold belt linked to gravitational collapse of the depocentre. This system is to be investigated during the AMARYLLIS-AMAGAS campaign of the R/V Marion Dufresne, to take place in...

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...

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...

A recently acquired multidisciplinary dataset comprising acoustic surveys (high-resolution sub-bottom profiles, multi-beam bathymetry, and broad band mid-water echo sounder), geochemistry (gas chemical and isotopic composition, porewater chemistry), and sedimentology (core lithology and X-ray CT) in the area of the Landsort deep (450 m of...

Fluid migration in sedimentary basins has profound effects on a range of geological processes, including the methane cycle, tectonic and sedimentary geohazards, and microbial communities in the oceans. The Alboran Sea is a tectonically active basin characterized by contourite drifts that host migrating fluids, expressed in places by pockmarks...

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 Amazon River extends from the Andes to the Atlantic continental margin and has the world's highest flux of suspended sediment and terrestrial organic carbon to the ocean, leading to the formation of one of the world's largest deep-sea turbiditic fans, 10 km thick, down to water depths of 4500 m. The fan is undergoing gravitational collapse,...

Le mouvement des fluides dans les bassins sédimentaires est associé à une série de processus géologiques, notamment le cycle du méthane, les géorisques tectoniques et sédimentaires et les communautés microbiennes du sous-sol. La mer d'Alboran, dans la partie occidentale de la Méditerranée, est connue pour être un bassin tectoniquement actif,...

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...

The Alboran Sea (Western Mediterranean) is a relatively small ocean basin connected with the Atlantic that provides a rich archive of tectonic and sedimentary processes at distinct temporal and spatial scales during the Quaternary. Since the collisional boundary of the Eurasia-Nubia plates crosses the Alboran Sea, this basin is also the locus...

In the southern margin of the Alboran Sea, the sedimentary succession over the past 1 Myr contains several submarine landslides. We observe that their geographical distribution does not appear to be related to the active Al Idrissi fault system (AIFS) responsible of the recent earthquakes (i.e. they are located more than 10 km away). The head...