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TitreContinental slope sedimentation adjacent to an ice margin. III. the upper Labrador Slope
AuteurHesse, R; Klauck, I; Khodabakhsh, S; Piper, D
SourceMarine Geology vol. 155, issue 3-4, 1999 p. 249-276,
Séries alt.Commission géologique du Canada, Contributions aux publications extérieures 1997203
ÉditeurElsevier BV
Documentpublication en série
Mediapapier; en ligne; numérique
SNRC3B; 3C; 13I; 13O; 13P; 14A; 14B; 14G; 14H; 14J; 14I; 14O; 14P
Lat/Long OENS -61.0000 -53.0000 62.0000 54.0000
Sujetstalus continental; dépôts glaciomarins; nappes glaciaires; profils sismiques; turbidites; moraines; charge de fond; chenaux d'eau de fonte; coulées de débris; marges glaciaires; hydrogéologie; géologie marine; paléontologie; sédimentologie; géologie des dépôts meubles/géomorphologie
Illustrationslocation maps; seismic reflection profiles; bar graphs; schematic diagrams; pie charts
Résumé(disponible en anglais seulement)
The upper Labrador Slope is the key area for sediment transfer from the northeastern margin of the Pleistocene Laurentide ice sheets (LIS) to the deep basin. It is subdivided from north to south into 8 sectors based on relief differences and echo-character on 750 line-km of continuous sleeve-gun and 3.5 kHz seismic profiles. High- to moderate-relief sectors 2 and 4 and, in part, 6 and 8 are seismically transparent and well stratified with continuous individual high-amplitude reflections and deep penetration; low-relief sectors 1, 3, 5 and 7 show strong bottom reflections and, with the exception of sector 1, low seismic penetration, poor stratification, and low-amplitude, if any, subbottom reflections. The lateral distribution of these alternating high- to moderate- and low-relief sectors reflects fundamental differences in the sediment transfer mechanisms through outlets from the LIS onto the slope. Low-relief slope sectors represent debrite and turbidite slopes and are located in front of ice-outlets on the slope and adjacent regions to the north. They originate from mass wasting on the upper slope of glacial detritus with a significant coarse component originally delivered as englacial or subglacial material and deposited in (end-) moraines or as bedload by subglacial or supraglacial rivers. High- to moderate-relief sectors originate from fall-out of suspended sediment from turbid surface-plumes (TSP) and preferentially occur off the southern half of outlets and south of major outlets, as exemplified by sector 2 south of the Hudson Strait outlet. This asymmetry is caused by the south-flowing Labrador Current, which entrains the buoyantly rising turbid meltwater-plumes at the glacier front. The present high-relief topography, which shows a dendritic pattern of upslope canyon branching, is the result of retrograde, headward canyon erosion by mass-wasting processes of an originally much smoother mud-blanket surface. The sediment is remobilized by slumping and entrained in debris flows and turbidity currents. The occurrence of TSP deposits on the high- to moderate-relief upper-slope sectors requires a summer sea surface not frozen over during major parts of the Pleistocene, including glacial maxima. TPS deposition on the upper slope, ice-rafting, and a plethora of ice-margin depositional phenomena, many of which give rise to mass-wasting and mass-flow phenomena, are the main features that make high-latitude continental slopes adjacent to continental ice-sheets different from their lower-latitude counterparts.