SILVA , Cleverson

Chronostratigraphic scheme illustrating the triggering periods of megaslides on the Amazon fan

SEAGAS is a 3-year initiative to study processes in the deep sea, involving research groups in Brazil and Europe, including in Germany. The project is being coordinated by PUCRS in collaboration with Géoazur in Nice, France. The hosts have complementary strengths in marine geoscience as applied to submarine gas hydrates, consistent with the...

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...

Synthesis of the triggering processes (simple vs multiple failure), the dynamics (fast vs slow) and volumes of megaslides on both the Amazon and Nile fans

The Amazon fan contains a gas hydrate province known from a bottom-simulating reflection (BSR) that lies within an upper slope compressional belt. In this study, the extent and character of the BSR and its relation to thrust-fold structures is examined using a grid of 2D and 3D seismic data. We show the BSR to comprise a series of elongate...

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...

The stability of natural gas hydrate accumulations on continental margins has mainly been considered in terms of changes in seawater pressures and temperatures driven from above by climate. We present evidence from the Amazon deep-sea fan for stability zone changes driven from below by fluid upwelling. A grid of 2D and 3D multichannel seismic...

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,...

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,...

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...