Seafloor morphology and sediment transfer in the mixed carbonate-siliciclastic environment of the Lesser Antilles forearc along Barbuda to St. Lucia

Type Article
Date 2020-10
Language English
Author(s) Seibert C.1, Feuillet N.1, Ratzov Gueorgui2, Beck C.3, Cattaneo AntonioORCID4
Affiliation(s) 1 : Université de Paris, Institut de physique du globe de Paris, CNRS, F-75005 Paris, France
2 : Géoazur, Université de Nice Sophia-Antipolis, CNRS, Observatoire de la Côte d'Azur, 250 rue Albert Einstein, 06560 Valbonne, France
3 : CNRS ISTerre, Université Savoie-Mont-Blanc, 73 376 Le Bourget du Lac, France
4 : IFREMER, Géosciences Marines, BP. 70, 29280 Plouzané, France
Source Marine Geology (0025-3227) (Elsevier BV), 2020-10 , Vol. 428 , P. 106242 (29p.)
DOI 10.1016/j.margeo.2020.106242
Keyword(s) Seafloor morphology, Backscatter, Submarine canyons, Landslides, Lesser Antilles arc

The Lesser Antilles arc is a mixed siliciclastic and carbonate active margin made of active volcanic and flat plio-quaternary carbonate islands. It was built as a result of a complex tectonic history at the slowly converging boundary between the American plates and the Caribbean plate. The sedimentary processes as a consequence of external forcing (earthquakes, volcanism, hurricanes) were rarely documented in such environment and are poorly understood. We exploited an exceptional dataset of high-resolution marine seafloor data acquired during the last 20 years in the northern part half of the Lesser Antilles forearc to document the sediment-transport processes. We achieved a detailed morpho-sedimentary study from multi-beam bathymetry, backscattering, and seismic profiles. Two areas could be characterized: 1) the “Rough Area”, along Barbuda to Guadeloupe carbonated islands, characterized by steep (up to 25°) slopes incised by short canyons, and deep basins controlled by major normal faults; 2) the “Channelized Area”, south of Guadeloupe and bordered by active volcanic islands and carbonate platforms, characterized by gentle slopes incised by long canyons. During sea-level high-stands, the sediments seem exported from the carbonate platform by hurricanes or density cascading but appear to settle at the shelf-edge and canyon heads. During sea-level low-stands, a connection may exist between onshore and offshore systems. However, this sediment supply appears not sufficient to generate canyon formation, likely shaped by regressive processes. Shelf breaks of the carbonate banks, platforms and submarine slopes are affected by sediment failures. Some may be associated to voluminous remobilizations and large mass transport deposits. Large earthquakes are likely the main processes in this area to remobilize sediments toward the deep forearc basins by triggering both slope failures and flushing of the canyon head.

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