Stratigraphie et dynamique sédimentaire de la plate-forme infra-littorale de Rivière-du-Loup; estuaire du Saint-Laurent

• Main Author: Lorrain, Stéphane
• Other Authors: d'Anglejan, Bruno (advisor)
• Format: Others
• Language: fr
• Published: McGill University 1992
• Subjects: Geology.
• Online Access: http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=56932

The stratigraphy of the sediments on the Riviere-du-Loup platform consists in a thin layer ( 8 phi), deposited between 5,800 y B.P. and 4,400 y B.P. The underlying pelitic sediments are made out of series of silt and clay microlaminations ($ approx$1 mm), separated by thin layers (2 to 5 mm) of fine sand (2 $<$ $ phi$ $<$ 3) originating either from ice rafted materials or turbid flows along the bottom during the spring thaw. Variations in the size composition of the material entering the estuary or fluctuations in currents during tidal cycles, could explain the formation of the series of microlaminations. === At present, the circulation pattern of the residual current is modulated by the fornightly tidal cycle. During the spring freshet, from mid-May to mid-June, the circulation pattern is altered, and the vector of the residual current is oriented upstream whereas it is usually oriented downstream. The solid discharges of the spring freshet (4,104 t.d$ sp{-1}$), neap tide (1,800 t.d$ sp{-1}$) and spring tide (2,592 t.d$ sp{-1}$), are sufficient to transport in 12 days, 28 days and 19 days respectively, the amount of sediment dredged annually in the riviere-du-Loup harbor (50 * 10$ sp3$ t). === The TSM fluctuations are mainly controlled by the resuspension of sediments deposited during slack tide (2,250 t at neap tide and 3,735 t at spring tide). Advection of TSM from the MTZ explains the variations in turbidity observed on the outer edge of the platform. Downstream of the study area, fluctuations of turbidity are controlled by advection of a turbid plume located at the mouth of the riviere du Loup.