GEOSCAN, résultats de la recherche


TitreEvolution and depositional structure of earthquake-induced mass movements and gravity flows: southern Orphan Basin, Labrador Sea
AuteurTripsanas, E K; Piper, D J W; Campbell, D C
SourceMarine and Petroleum Geology vol. 25, 2008 p. 645-662,
Séries alt.Secteur des sciences de la Terre, Contribution externe 20060350
ÉditeurElsevier BV
Documentpublication en série
Mediapapier; en ligne; numérique
ProvinceRégion extracotière de l'est
Lat/Long OENS-50.0000 -47.0000 49.5000 48.0000
Sujetstalus continental; dépôts de pentes; glissements de pentes; stabilité des pentes; analyses de la stabilité des pentes; caractéristiques sous-marines; canyons sous-marins; turbidites; courants de turbidite; coulées de débris; glissements de terrain; dépôts de glissement de terrain; levés géophysiques; levés sismiques; levés sismiques marins; profils sismiques; levés de reflexion sismiques; gîtes en forme de traînée; milieu sédimentaire; Holocène; Pléistocène; géologie marine; géologie des dépôts meubles/géomorphologie; stratigraphie; géophysique; Cénozoïque; Quaternaire
Illustrationslocation maps; stratigraphic columns; photographs; cross-sections; seismic profiles
ProgrammeLes géosciences à l'appui de la gestion des océans
Résumé(disponible en anglais seulement)
A series of submarine canyons on the southwest slope of Orphan Basin experienced complex failure at 7-8 cal ka that resulted in the formation of a large variety of mass-transport deposits (MTDs) and sediment gravity flows. Ultra high-resolution seismic-reflection profiles and multiple sediment cores indicate that evacuation zones and sediment slides characterize the canyon walls, whereas the canyon floors and inner banks are occupied by cohesive debris-flow deposits, which at the mouths of the canyons on the continental rise form large, coalescing lobes (up to 20 m thick and 50 km long). Erosional channels, extending throughout the length of the study area (< 250 km), are observed on the top of the lobes. Piston cores show that the channels are partially filled by poorly sorted muddy sand and gravel, capped by inversely to normally graded gravel and sand. Such deposits are interpreted to originate from multi-phase gravity flows, consisting of a lower part behaving as a cohesionless debris flow and an upper part that was fully turbulent.

The Holocene age and the widespread synchronous occurrence of these failures indicate a large magnitude earthquake as their possible triggering mechanism. The large debris-flow deposits on the continental rise originated from large failures on the upper continental slope, involving proglacial sediments. Retrogression of these failures led to the eventual failure of marginal sandy till deposits on the upper slope and outer shelf, which due to their low cohesion disintegrated into multi-phase gravity flows. The evacuation zones and slide deposits on the canyon walls were triggered either by the earthquake, or from erosion at the foot of the canyon walls by the downdip flowing debris flows. The available data show that the slides, debris-flows, and multi-phase gravity flows observed in this study are petrographically different, indicating different sediment sources. This indicates that not all failures lead through flow transformation to the production of a multi-phase gravity flow, but only when the sediment source contains ample coarse-grained material. The spatial segregation of the slide, debris-flow, and multi-phase gravity-flow deposits is attributed to the different mobility of each transport process.