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TitreRole of the bedrock topography in the Quaternary filling of a giant estuarine basin: the Lower St. Lawrence Estuary, Eastern Canada
AuteurDuchesne, M J; Pinet, N; Bédard, K; St-Onge, G; Lajeunesse, P; Campbell, D C; Bolduc, A
SourceBasin Research vol. 22, no. 6, 2010 p. 933-951,
Séries alt.Secteur des sciences de la Terre, Contribution externe 20090103
Documentpublication en série
Mediapapier; en ligne; numérique
Lat/Long OENS-70.0000 -67.0000 49.5000 48.0000
Sujetsbassins; bassins sédimentaires; développement du bassin; géométrie du bassin; dépôts estuairiens; études estuairiennes; estuaires; sédiments marins; sédiments marins; levés sismiques marins; levés sismiques; levés géophysiques; levés de reflexion sismiques; bathymétrie; topographie du fond océanique; topographie du fond océanique; Bassin du bas de l'estuaire du Saint-Laurent; géologie marine; géophysique; géologie des dépôts meubles/géomorphologie; Cénozoïque; Quaternaire
Illustrationslocation maps; profiles; seismic profiles
ProgrammeLes géosciences à l'appui de la gestion des océans
Résumé(disponible en anglais seulement)
The geometry of estuarine and/or incised-valley basins and their protected character compared with open sea basins are favourable for the preservation of sedimentary successions. The Lower St. Lawrence Estuary Basin (LSLEB, eastern Canada) is characterized by a thick (>400 m in certain areas) Quaternary succession. High- and very high-resolution seismic reflection data, multibeam bathymetry coverage completed by core and chronostratigraphic data as well as a 3-D seismic stratigraphic model are used to document the geometrical relationships between the bedrock and the Quaternary units of the LSLEB. The bedrock geometry of LSLEB is characterized by two large troughs that are interpreted as resulting mainly from repeated (?) periods of glacial overdeepening of a pre-Quaternary drainage system. However, other mechanisms with complex feedback effects such as differential glacio-isostatic uplift, erosion, sedimentary supply, and subsidence may have contributed to the formation of bedrock troughs. The two large bedrock troughs are mostly filled by ~200 m thick Wisconsinan (Marine Isotopic Stages 2 - 4) and possibly older sediments. Overlying units recorded the retreat of the Laurentian Ice Sheet during the Late Wisconsinan (Marine Isotopic Stage 2) and estuarine conditions during the Holocene. The strong correlation existing between the bedrock topography and the thickness of the Quaternary succession is indicative of the effectiveness of the LSLEB as a sediment trap.