GEOSCAN, résultats de la recherche


TitreLate glacial fans in the eastern Skagerrak; depositional environment interpreted from swath bathymetry and seismostratigraphy
AuteurLongva, O; Olsen, H A; Piper, D J W; Rise, L; Thorsnes, T
SourceMarine Geology vol. 251, 2008 p. 110-123,
Séries alt.Secteur des sciences de la Terre, Contribution externe 20070107
ÉditeurElsevier BV
Documentpublication en série
Mediapapier; en ligne; numérique
Lat/Long OENS 7.0000 10.5000 59.0000 57.5000
Sujetscônes alluviaux; cônes sous-marins; dépôts glaciaires; tills; coulées de débris; interpretations sismiques; levés sismiques; profils sismiques; levés de reflexion sismiques; levés sismiques marins; bathymétrie; milieu sédimentaire; antecedents de sedimentation; topographie du fond océanique; topographie du fond océanique; géologie marine; géologie des dépôts meubles/géomorphologie; géophysique; stratigraphie; Cénozoïque; Quaternaire
Illustrationsseismic profiles; location maps; tables
ProgrammeLes géosciences à l'appui de la gestion des océans, Aléas géologiques et contraintes à la mise en valeur des ressources extracôtières
Résumé(disponible en anglais seulement)
The origin of acoustically transparent fan deposits overlying glacial till and ice-proximal sediments on the southern margin of the Norwegian Channel has been studied using high-resolution seismic-reflection profiles and multibeam bathymetry. The first deposits overlying glacigenic sediments are a series of stacked, acoustically transparent submarine fans. The lack of glaciomarine sediments below and between individual fans indicates that deposition was rapid and immediately followed the break up of the Late Weichselian ice
cover. The fans are overlain by stratified glaciomarine sediments and Holocene mud. Because of the uniformity of this drape, the upper surface of the fan deposits is mimicked at the present seafloor, and the bathymetric images clearly show the spatial relationship of the fans to bedrock ridges and the presence of braided channellevee systems on the surface of the youngest fans. The acoustically transparent character of the fan deposits indicates that they comprise silt and clay, and their lobate form and lack of internal stratification indicates that they were deposited by debris flows. The channel-levee morphology indicates deposition from more watery hyperconcentrated fluid flows. The fan sediments were either derived from 1) erosion of MidWeichselian lake deposits in southern Skagerrak or 2) from Late glacial ice-margin lake deposits, ponded against the Norwegian Channel ice stream, which collapsed catastrophically when the lateral support was removed as the ice disintegrated. Fans composed almost exclusively of fine-grained sediment need not, therefore, rule out an origin in a deglacial setting relatively close to the former margins of glaciers and ice sheets.