SEDLAB
Référence sismer
http://dx.doi.org/10.17600/18000401Informations générales
Chefs de mission
- Etienne Samuel (Leg 1)
- Etienne Samuel (Leg 2)
Date et lieu de départ
Date et lieu d'arrivée
Etape | Date de départ | Date d'arrivée | Départ | Arrivée | Navire |
---|---|---|---|---|---|
Leg 1 | Sat Apr 07 00:00:00 CEST 2018 | Thu Apr 19 00:00:00 CEST 2018 | Nouméa (Nouvelle-Calédonie) | Nouméa (Nouvelle-Calédonie) | Alis |
Leg 2 | Sat Apr 21 00:00:00 CEST 2018 | Sat May 05 00:00:00 CEST 2018 | Nouméa (Nouvelle-Calédonie) | Nouméa (Nouvelle-Calédonie) | Alis |
Objectifs :
Travaux effectués :
Remerciements :
La campagne SEDLAB a été financée par le Ministère de l’Enseignement supérieur et de la recherche, à travers la Commission Nationale de la Flotte Hauturière. Un fond de soutien octroyé par la CNFH et par le Gouvernement de la Nouvelle-Calédonie a aussi permis le déplacement des scientifiques et l’acheminement d’une partie matériel vers et depuis Nouméa.
L’ensemble de l’équipe scientifique remercie le Commandant de l’ALIS, Frédéric RANNOU, son second Loic GOFF, ainsi que tout l’équipage du navire.
Emmanuel de SAINT LEGER, Éric MACE, Lionel FICHEN et la division technique de l’INSU/CNRS sont remerciés pour la mise à disposition du carottier Küllenberg.
Sarah SAMADI (Museum National d’Histoire Naturelle) et Thomas BRIDGE (James Cook University) sont remerciés pour leur intérêt dans la campagne.
Enfin, l’ADECAL Technopole et le Service Géologique de Nouvelle-Calédonie sont remerciés pour leur aide tout au long du projet.
Bibliographie
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Etienne S., Le roy P., Tournadour E., Roest W.R., Jorry S., Collot J., Patriat M., Largeau M.A., Roger J., Clerc C., Dechnick B., Sanborn K.L., Lepareur F., Horowitz J., Webster J.M. & Gaillot A. 2021. Large-scale margin collapses along a partly drowned, isolated carbonate platform (Lansdowne Bank, SW Pacific Ocean). Marine Geology 436: 106477. DOI:10.1016/j.margeo.2021.106477
Résumé [+] [-]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 kmwide 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 affect a terrace located in 70 m water depth around the bank, which, depending on its age and origin, could provide a minimum age for collapse events. Finally, considering the shallow water depth of failure headscarps, the volumes of material involved in the slides as well as their vicinity to the nearby main island of New Caledonia, numerical simulations of the tsunamigenic potential of submarine slides have been performed. They showed that these slides would have been able to produce a meter-scale wave that would reach the northern coast of the island in less than an hour.
Campagnes accessibles citées (1) [+] [-]
Liste des photos
Liste des participants
Par étape :
- Leg 1 (Sat Apr 07 00:00:00 CEST 2018 - Thu Apr 19 00:00:00 CEST 2018) Navire : Alis
- Clerc, Camille (Géologie, Université de la Nouvelle-Calédonie)
- Etienne, Samuel (Sédimentologie, ADECAL Technopole)
- Chef de mission
- Leroy, Pascal (Géophysique, Université de Bretagne-Occidentale)
- Co-chef de mission
- Patriat, Martin (Géologie, Institut français de recherche pour l'exploitation de la mer)
- Roest, Walter (Géophysique, Institut français de recherche pour l'exploitation de la mer)
- Sanborn, Kelsey ( The University of Sydney)
- Leg 2 (Sat Apr 21 00:00:00 CEST 2018 - Sat May 05 00:00:00 CEST 2018) Navire : Alis
- Collot, Julien (Géophysique, Service Géologique de Nouvelle-Calédonie)
- Co-chef de mission
- Dechnik, Belinda (Sédimentologie, The University of Sydney)
- Etienne, Samuel (Sédimentologie, ADECAL Technopole)
- Chef de mission
- Horowitz, Jeremy (Spécialiste des coraux, James Cook University)
- Largeau, Maria (Etudiante, bathymétrie, Intechmer)
- Lepareur, Fanny ( UMS PatriNat (OFB-CNRS-MNHN))
Cartographie des stations de collectes
Liste des stations
Taxons par accès
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