Éditeur(s) : Elsevier Science Bv
Résumé : Recent oceanographic surveys revealed the existence of five volcaniclastic deep-sea fans off La Reunion Island. The Cilaos fan is a large volcaniclastic submarine fan, connected to rivers that episodically experience torrential floods through a narrow and steep shelf-slope system. New piston cores presented in this study together with echosounder profiles give new insight into the evolution, of this extensive and sand-rich turbidite system. The Cilaos fan extends over 15,000 km(2) on an abyssal plain and is compartmentalized by topographic highs. Located southwest of the island, the sedimentary system consists of a canyon area and a deep sea fan divided into a proximal and a distal fan. The proximal fan is characterized by its wide extent and coarse-grained turbidites. The distal fan is characterized by elongated structures and fine-grained turbidites. A detailed morphological study of the fan which includes the analysis of swath bathymetry, backscatter, echosounder, and piston core data shows that the Cilaos fan is a complex volcaniclastic deep-sea fan, highly influenced by preexisting seafloor irregularities. The canyons and the slope area show a complex and evolving sediment feeding system with a direct sediment input by the river and irregular sediment supply by submarine landslide. Three main construction stages are identified for this system: (1) an old incision phase of the channels forming wide turbidites extending over the entire distal fan; (2) a period of no or low activity characterized by a thick layer of hemipelagic mud; and (3) a local reactivation of the channel in the proximal fan. Each stage seems to be linked to a different sediment source with a progressively increasing contribution of hemipelagic sediment and mud in younger stages. (C) 2011 Elsevier B.V. All rights reserved.
Marine Geology (0025-3227) (Elsevier Science Bv), 2011-10 , Vol. 288 , N. 1-4 , P. 1-17

Droits : 2011 Elsevier B.V. All rights reserved.
http://archimer.ifremer.fr/doc/00056/16704/14203.pdf
DOI:10.1016/j.margeo.2011.06.011
http://archimer.ifremer.fr/doc/00056/16704/

Éditeur(s) : Elsevier Science Bv
Résumé : Volcaniclastic successions are well-described in volcanic arc setting but rare in hotspot environments. The present work proposes a facies model of volcaniclastic sedimentation related to basaltic hotspot volcanoes as exemplified by the Piton de la Fournaise volcano (La Réunion Island). The facies model is based on a multi-scale approach combining high-resolution multibeam and backscatter data, deep-water photographs, side scan imagery and Kullenberg piston cores. Data show that a wide range of gravity flows and erosional features develop in the active volcaniclastic sedimentary system. Coastal and submarine instabilities are the main processes shaping the volcano's submarine morphology. Meanwhile, the evolution and dynamics of the sedimentary system are strongly linked with the morpho-structural evolution of the subaerial part of the volcano. The proposed model is characterized by a cyclic succession of stages: (1) a growing stage during which sedimentary activity is mainly restricted to proximal and mid-slope areas; (2) a collapse stage that entirely reshapes the morphology of the submarine slopes; and (3) an erosional stage related to a slow down of volcanic activity, enabling the development of large deep-sea fans.
Marine Geology (0025-3227) (Elsevier Science Bv), 2013-03 , Vol. 337 , P. 35-52

Droits : 2013 Published by Elsevier B.V. All rights reserved
http://archimer.ifremer.fr/doc/00137/24798/22939.pdf
DOI:10.1016/j.margeo.2013.01.004
http://archimer.ifremer.fr/doc/00137/24798/