The key to Understand Submarine Canyon Evolution

HR: 1340h
AN: OS23C-1326 [Abstracts]
TI: The key to Understand Submarine Canyon Evolution
AU: * Baztan, J
EM: jbaztan@ifremer.fr
AF: Inst. Univ.Europeen Mer, UMR6538,Domaines OcＢniques, Place Nicolas Copernic, Plouzane, 29280 France
AU: * Baztan, J
EM: jbaztan@ifremer.fr
AF: IFREMER, DRO-GM, BP-70, Plouzane, 29280 France
AU: Berne, S
EM: sberne@ifremer.fr
AF: IFREMER, DRO-GM, BP-70, Plouzane, 29280 France
AU: Olivet, J
EM: Jean.Louis.Olivet@ifremer.fr
AF: IFREMER, DRO-GM, BP-70, Plouzane, 29280 France
AU: Rabineau, M
EM: mrabinea@univ-brest.fr
AF: Inst. Univ.Europeen Mer, UMR6538,Domaines OcＢniques, Place Nicolas Copernic, Plouzane, 29280 France
AU: Rabineau, M
EM: mrabinea@univ-brest.fr
AF: IFREMER, DRO-GM, BP-70, Plouzane, 29280 France
AU: Aslanian, D
EM: Daniel.Aslanian@ifremer.fr
AF: IFREMER, DRO-GM, BP-70, Plouzane, 29280 France
AB: Submarine canyons are the preferential path of sediment transfer from the shelf to the deep sea, they are the key to understand the source-to-sink sedimentation and, in consequence, the shelf, slope and rise evolution. Pioneer works on submarine canyons described and proposed hypothesis to explain the formation and evolution of them. However, submarine canyons remain a matter of speculation. Our work in the Gulf of Lions (Mediterranean Sea) is based on swath bathymetry data together with sub-bottom profiles, high resolution seismic reflection profiles and cores. These data allow a detailed morphologic and stratigraphic study from the shelf to the rise through time, from 2.600.000 yrs to present. We show that two main erosive features, of very different dimensions, constitute the canyons: the axial incision and the canyon's major valley. The axial incision is interpreted as an erosive path related to the passage of hyperpycnal turbidity currents, generated up-slope by river connection. In the Gulf of Lions such currents are most likely to have formed during each Glacial Maxima (with a cyclicity of 100.000 years for the last 900.000 years and 40.000 years between 900.000 and 2.600.000 years) as both proximity of the shoreline (due to the lowstand of sea level) and high detrital sediment supply (due to glacial abrasion upstream) increased the flow of sediments delivered to the canyon heads. The axial incisions observed at the sea floor and fossil incisions observed on seismic lines, are related to equivalent conditions. The axial incision activity has a key influence on canyon evolution, it triggers mass wasting that affect the canyon's major valley (head and flanks) allowing the progressive widening and deepening of the canyon. Consequently the canyon's major valley (typically bounded by flanks of more than 700 meters in height) is the result of the axial incision activity through successive lowering of sea level. In summary: our cross-disciplinary approach (morphology, seismic stratigraphy, sedimentology and glacioeustacy) provides a regional and detailed vision of canyons. This work (i) explains the mechanism that controls the evolution of the submarine canyons and the sediment transfer from the shelf to the rise and (ii) shows the sedimentary evolution of the margin (from source to sink) in relation with sea level changes from 2.600.000 years to present.
DE: 3022 Marine sediments--processes and transport
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting