9:30 AM - 9:45 AM
[SIT07-03] Seafloor subsidence and mantle dynamics
The variations of the mid-oceanic ridge depths are well recovered by the modeled dynamic topography. The systematic fit of the bathymetry allows the recovery of the subsidence rate, from which we derive the effective thermal conductivity, keff. This parameter ranges between 1 and 7 Wm-1K-1. We show that departures from the keff=3 Wm-1K-1 standard value are systematically related to mantle convection and not to the lithospheric structure. Regions characterized by keff>3 Wm-1K-1 are associated with the uplift of mantle plumes. Regions characterized by keff<3 Wm-1K-1 are related to large scale mantle downwellings such as the Australia-Antarctic Discordance (ADD) or the return flow from the South Pacific Superswell to the East Pacific rise. This demonstrates that the mantle dynamics plays a major role in the shaping of the oceanic seafloor. In particular, the parameters generally considered to quantify the lithosphere structure, such as the thermal conductivity, are not only representative of this structure but also incorporate signals from the mantle convection occurring beneath the lithosphere.