| Summary: | Sediments contained in fjords have a high potential to reconstruct paleoenvironmental changes since these glacial valleys located at the interface of continent and ocean are generally characterized by high sedimentation rates. Fjords are long narrow valleys that were deeply incised during successive glaciations and interglacial periods. They typically contain glacial deposits and landforms that inform on past variations of ice margins. Fjords can also exist in lacustrine environments, such as in alpine area or formerly glaciated regions, where the glacio-isostatic rebound combined with the postglacial marine regression isolated the fjord from the sea. Many fjord-lakes are found in Québec and Labrador, but the evolution of these lacustrine basins since deglaciation is poorly documented, as many worldwide analogues of these type of lakes are still glaciated today, or are located in alpine regions where no marine transgression ever occurred. Hydroacoustic technologies such as multibeam bathymetry and sub-bottom profiles allow visualizing at a high resolution the morpho-stratigraphy of subaquatic basins in order to interpret the major events that modeled their basins and lead to a better understanding of their past and modern sedimentary dynamics. Using such an approach in fjord-lakes located at key locations would also allow refining history of last glaciation in areas where only few paleoenvironmental studies exist. This thesis reports and describes multibeam bathymetry data and sub-bottom profiles collected in eight fjord-lakes of Québec (lakes Mékinac, Jacques-Cartier, Pohénégamook, Témiscouata, Pentecôte, Walker & Pasteur) and Labrador (Grand Lake), as well as Digital Elevation Model (DEM) of their valleys and surrounding areas. The analysis that combine geomorphology and sismo-stratigraphy allow: 1) reconstructing the sequence of deglaciation in Mauricie (Southern Québec) and eastern Labrador; 2) refining the location of the Mars-Batiscan morainic belt as well as the transgression limit of the deglacial ...
|
|---|