Direct sediment transfer from land to deep-sea: Insights into shallow multibeam bathymetry at La Réunion Island
|Author(s)||Babonneau Nathalie1, Delacourt Christophe1, Cancouet R.1, Sisavath Emmanuelle2, 3, Bachelery Patrick2, 4, Mazuel Aude1, Jorry Stephan3, Deschamps Anne1, Ammann Jerome1, Villeneuve N.2|
|Affiliation(s)||1 : Univ Brest, Inst Univ Europeen Mer, UBO, UMR CNRS Domaines Ocean 6538, F-29280 Plouzane, France.
2 : Univ Reunion, IPG Paris, UMR CNRS 7154, Lab Geosci Reunion, F-97715 St Denis Messag 9, Reunion, France.
3 : IFREMER, Geosci Marines, Lab Environm Sedimentaires, F-29280 Plouzane, France.
4 : Univ Clermont Ferrand, Observ Phys Globe Clermont Ferrand, UMR CNRS IRD 6524, Lab Magmas & Volcans, F-63038 Clermont Ferrand, France.
|Source||Marine Geology (0025-3227) (Elsevier Science Bv), 2013-12 , Vol. 346 , P. 47-57|
|WOS© Times Cited||43|
|Keyword(s)||submarine canyon, canyon head, turbidity current, hyperpycnal flow, coastal instability|
|Abstract||Submarine canyon heads are key areas for understanding the triggering factors of gravity currents responsible for the transfer of detrital sediment to the deep basins. This contribution offers a detailed picture of canyon heads off La Réunion Island, with high-resolution multibeam bathymetry in the water depth range of 4–220 m. The present feeding of the Cilaos turbidite system, one of the largest modern volcaniclastic systems in the world, is deduced from morphological and sedimentological interpretations of newly acquired data. The study highlights small-scale sedimentary features indicating hydrodynamic and sedimentary processes.A direct connexion between the Saint-Etienne river mouth and submarine canyons is evidenced by the complete incision of the shelf and the presence of canyon heads connected to the modern deltaic bar. This direct connection, supplied by river torrential floods (cyclonic floods every two or three years), suggests the continuity of high-density fluvial flows to submarine gravity flows, forming hyperpycnal flows in the canyon.The initiation of secondary submarine gravity flows by storm waves (large austral waves and cyclonic waves) is also proposed for submarine canyons with large canyon heads developed in the surf zone from a sandy coastal bar. Bedforms in active canyon axis are considered as an indicator of the frequent activity of high-density turbidity currents.Moreover, a morphological record of last glacial and deglacial sea level variations is preserved, and particularly the Last Glacial Maximum sea level with the presence of small vertical cliffs, observed in this bathymetric data, which likely corresponds to a paleo-shoreline or paleo-reefs.|