Large-scale margin collapses along a partly drowned, isolated carbonate platform (Lansdowne Bank, SW Pacific Ocean)
In: ISSN: 0025-3227 ; Marine Geology ; https://hal-insu.archives-ouvertes.fr/insu-03211738 ; Marine Geology, 2021, 436, pp.106477. ⟨10.1016/j.margeo.2021.106477⟩, 2021
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International audience ; The Lansdowne Bank is a partly drowned, isolated carbonate platform of around 4000 km2 located 300 km west of New Caledonia, in the SW Pacific Ocean, in water depths of 20 to 100 m. New multibeam bathymetric data, high resolution seismic reflection profiles and sediment gravity cores have been acquired on the bank top and adjacent slopes. This dataset reveals an almost continuous 4 km wide outer reef rim located in ca. 50 m water depth, surrounding a gently deepening inner platform, reaching up to 100 m water depth. The bank is bordered by very steep slopes showing numerous erosional morphologies such as canyons, channels and gullies. Along with these bypass features, spectacular bank margin collapses and slope failures are evidenced by up to 20 km-wide bank edge and intraslope failure scars, respectively, resulting in a typical “scalloped” geometry of the bank margin. These failure scars can lead to a complete collapse of the outer reef rim and impact subsequent reef development. Bank margin collapses are evidenced by hectometer to kilometer-scale blocks and debris shed on the slope, likely emplaced by rock fall/avalanching processes originating from the brittle failure of early cemented bank edge and upper slope sediments. In turn, failures triggered on the un-cemented mud-prone middle to lower slopes likely generate more cohesive, submarine debris flows that could be at the origin of erosive morphologies within the debris fields. Estimated individual failure volumes can reach up to 3 km3. Quaternary sea-level lowstands, that would have led to platform exposure, fracturing and karstification, and the development of an erosional sea cliff, as well as subsequent rising sea-level are believed to play a significant role in mass wasting event emplacement, yet “bottom up” submarine processes such as the upslope propagation of bypass morphologies by retrogressive headward erosion cannot be ruled out. In terms of geomorphic and stratigraphic constraints, the documented bank margin collapses ...
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Large-scale margin collapses along a partly drowned, isolated carbonate platform (Lansdowne Bank, SW Pacific Ocean)
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Autor/in / Beteiligte Person: | Etienne, Samuel ; Le Roy, Pascal ; Tournadour, Elsa ; Roest, Walter ; Jorry, Stephan ; Collot, Julien ; Patriat, Martin ; Largeau, Maria ; Roger, Jean ; Clerc, Camille ; Dechnick, Belinda ; Sanborn, Kelsey ; Lepareur, Fanny ; Horowitz, Jeremy ; Webster, Jody ; Gaillot, Arnaud ; Geological Survey of New Caledonia ; Department of Industry Mines and Energy ; ADECAL, TECHNOPOLE ; Domaines Océaniques (LDO) ; Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Observatoire des Sciences de l'Univers-Institut d'écologie et environnement-Centre National de la Recherche Scientifique (CNRS) ; Géosciences Marines (GM) ; Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER) ; Institut de Recherche pour le Développement (IRD Nouvelle-Calédonie ) ; Institut de sciences exactes et appliquées (ISEA) ; Université de la Nouvelle-Calédonie (UNC) ; Muséum national d'Histoire naturelle (MNHN) |
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Zeitschrift: | ISSN: 0025-3227 ; Marine Geology ; https://hal-insu.archives-ouvertes.fr/insu-03211738 ; Marine Geology, 2021, 436, pp.106477. ⟨10.1016/j.margeo.2021.106477⟩, 2021 |
Veröffentlichung: | HAL CCSD ; Elsevier, 2021 |
Medientyp: | academicJournal |
DOI: | 10.1016/j.margeo.2021.106477 |
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