GEOSCAN, résultats de la recherche


TitreDimensions and architecture of late Pleistocene submarine lobes off the northern margin of east Corsica
AuteurDeptuck, M E; Piper, D J W; Savoye, B; Gervais, A
SourceSedimentology vol. 55, 2008 p. 869-898, (Accès ouvert)
Séries alt.Secteur des sciences de la Terre, Contribution externe 20070110
Documentpublication en série
Mediapapier; en ligne; numérique
Lat/Long OENS 9.0000 10.5000 43.0000 42.0000
SujetsPléistocène; dorsales sous-marines; caractéristiques sous-marines; hauts-fonds sous-marins; cônes alluviaux; cônes sous-marins; sedimentation; levés sismiques; profils sismiques; profils sismiques marins; turbidites; talus continental; dépôts de pentes; géologie marine; combustibles fossiles; géophysique; stratigraphie; Cénozoïque; Quaternaire
Illustrationslocation maps; seismic profiles; tables; plots; stratigraphic columns; schematic diagrams
ProgrammeLes géosciences à l'appui de la gestion des océans, Aléas géologiques et contraintes à la mise en valeur des ressources extracôtières
Diffusé2008 01 03
Résumé(disponible en anglais seulement)
Sandy lobe deposits on submarine fans are sensitive recorders of the types of sediment gravity flows supplied to a basin and are economically important as hydrocarbon reservoirs. This study investigates the causes of variability in 20 lobes in small late Pleistocene submarine fans off East Corsica. They were imaged using ultra-high resolution boomer seismic profiles (< 1 m vertical resolution) and sediment type was groundtruthed using piston cores published in previous studies. Repeated crossings of the same depositional bodies were used to measure spatial changes in their dimensions, geometry and architecture. Most lobes increase abruptly down-slope to a peak thickness between 8 and 42 m, beyond which they show a progressive, typically more gradual decrease in thickness until they thin to below seismic resolution or pass into draping facies of the basin plain. Lobe areas range from 3 to 70 km2 and total lengths from 2 to 14 km, with the locus of maximum sediment accumulation from 3 to 28 km from the shelf-break.
Based on their location, dimensions, internal architecture, and nature of the feeder channel, the lobes are divided into two end-member types. The first are small depositional bodies located in proximal settings, clustered near the toe-of-slope and fed by short-lived slope gullies or erosive channels lacking or with poorly developed levees. The second are larger, architecturally more complex, depositional bodies deposited in more distal settings, outboard of more stable and longer-lived leveed fan valleys. Hybrid lobe types are also observed. At least three hierarchical levels of compensation stacking are recognised. Individual beds and bed-sets stack to form lobe-elements; lobe-elements stack to form composite lobes; and composite lobes stack to form lobe complexes. The broad-scale differences in lobe dimensions, location, and architectural complexity reflect differences in the properties of submarine sediment gravity flows (volume, duration, concentration, velocity) and their degree of variation through time, combined with the number of flows contributing to the lobe prior to avulsion or abandonment (related to the stability of the feeder conduit and the seafloor morphology outboard the channel mouth). In general, lobes outboard stable fan valleys that are connected to shelf-incised canyons have longer lifespans, are larger and are architecturally more complex.