Conférence GM & ED Gaïa :
‘Bottom-up’ gas hydrate dynamics and seafloor fluid venting in collapsing deep-sea fans. Examples from the Amazon and Nile

par Daniel PRAEG

Géoazur, Nice.

à 14h amphi 23.01 campus Triolet – Université de Montpellier

Participer à la conférence Zoom (ID de réunion : 93757873200)

Gas hydrates frozen within deep-sea sediments form the largest reserve of carbon (mainly methane) on Earth. Their stability over time is sensitive to pressure and temperature changes, with strong implications for global methane cycling and continental slope stability. Submarine gas hydrate dynamics are usually seen in relation to ‘top-down’ changes in water column properties (sea level, temperatures), driven from above by climate. However, gas hydrate stability is also influenced from below by fluid migration within sedimentary successions. The Amazon and Nile deep-sea fans are rapidly-deposited depocentres that contain tectonic structures recording their gravitational collapse, as well as gas hydrate provinces associated with seafloor fluid vents. ‘Bottom-up’ changes in fluid expulsion and gas hydrate stability linked to tectonic movements may account for the giant landslides that characterize these and other deep-sea fans. Results are presented from French-Brazilian collaborations involving Géoazur, including initial results from the AMARYLLIS-AMAGAS campaign to the Amazon deep-sea fan in May-June 2023.

Daniel PRAEG is a marine geoscientist with interests in sedimentary and tectonic processes on continental margins in relation to geofluids. Originally a glacial geologist (meltwater drainage), his current focus is on the submarine cryosphere (gas hydrates). He is from Canada, and has lived and worked in the USA, Scotland (PhD 1997), Ireland, Italy, Brazil and France.