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Following the flood of July 1996, a significant quantity of sediment, coming from the catchment areas contiguous to the Saguenay fjord, was discharged in the Baie des Ha! Ha! and the North Arm. To characterize the mode of deposit and the potential for remobilization of these deposits, a series of cores was taken in the fjord using a box corer and a gravity corer during the summers of 1997 and 1998. These cores have been analyzed by the axial tomodensitometer at the Regional Hospital Center of Rimouski. The use of the tomodensitometer in geology allows a nondestructive study of the sample and a qualitative and quantitative evaluation of the density of the sediments, their mode of deposition, and their compaction. The study of the upper 45 cm of sediments shows the presence, in the uppermost layer, of several facies type characteristics of a gravity deposit. This layer rests on an erosional unconformity cut into the surface of the older deposits, themselves of gravity type. One year after the flood, no trace of reworking could be detected in the upper part of the cores. Nevertheless, cores taken in the summer of 1998 show a significant reworking of the superficial sediments in direct relation with bioturbation. No reworking of hydrodynamic origin was observed.Key words: scanography, flood, turbidity currents, sedimentary structures, compaction, bioturbation.Suite aux crues de juillet 1996, une importante quantité de sédiment provenant des bassins versants contigus au fjord Saguenay s'est déversée dans la baie des Ha! Ha! et dans le bras nord. Afin de caractériser le mode de mise en place et le potentiel de remobilisation de ces dépôts, une série de carottes a été prélevée, dans le fjord, à l'aide d'un carottier-boîte et d'un carottier à gravité durant l'été 1997 et 1998. Ces carottes ont été analysées à l'aide du tomodensitomètre axial du Centre Hospitalier Régional de Rimouski. L'utilisation du scanographe (ou tomodensitomètre) permet une évaluation qualitative et quantitative de la densité des sédiments, de leur mode de mise en place et de leur état de compaction. Les 45 cm supérieurs des dépôts représentent, dans la couche nouvellement déposée, plusieurs types de faciès caractéristiques d'un mode de dépôt gravitaire. La base de cette couche repose en discordance érosionelle sur des dépôts plus anciens de même type. Un an après la crue, aucune structure superficielle de remaniement n'a pu être décelée dans la partie sommitale des carottes. Néanmoins, des carottes prélevées en été 1998 montrent un remaniement important des sédiments de surface en relation directe avec la bioturbation. Aucun remaniement d'origine hydrodynamique n'a été observé.Mots clés : scanographie, crue, turbidites, structures sédimentaires, compaction, bioturbation. [ABSTRACT FROM AUTHOR]

ABSTRACT: Autogenic controls have significant influence on deep-water fans and depositional lobes morphology. In this work, we aim to investigate autogenic controls on the topography and geometry of deep-water fans. The influence of the sediment concentration of turbidity currents on deep-water fans morphology was also investigated. From the repeatability of 3D physical modeling of turbidity currents, two series of ten experiments were made, one of high-density turbidity currents (HDTC) and another of low-density turbidity currents (LDTC). All other input parameters (discharge, sediment volumetric concentration and grain size median) were kept constant. Each deposit was analyzed from qualitative and quantitative approaches and statistical analysis. In each experimental series, the variability of the morphological parameters (length, width, L/W ratio, centroid, area, topography) of the simulated deep-water fans was observed. Depositional evolution of the HDTC fans was more complex, showing four evolutionary steps and characterized by the self-channelizing of the turbidity current, while LDTC fans neither present self-channelizing, nor evolutionary steps. High disparities on the geometrical parameters of the fans, as characterized by the elevated relative standard deviation, suggest that autogenic controls induced a stochastic morphological behaviour on the simulated fans of the two experimental series.