Marine records of riverine water and sediment discharge in fjords of Nunatsiavut

This thesis focuses on the understanding of patterns and variability of sediment and fresh water delivery from land to sea, and sediment dispersal in the marine basins of two fjords in Northern Labrador. Multibeam and sub-bottom acoustic data and sediment cores were collected in Nachvak and Saglek fjords. Sediment cores were sub-sampled for X-radiography, grain size, and radiochemical analysis (based on the particle-bound radioisotopes 210Pb and 137Cs,), to study sedimentary structures and determine sediment accumulation rates. Results show that the sediments are generally mottled and fine grained. Sediment accumulation rates are on average 0.21 cm/y in Nachvak fjord and 0.26 cm/y in Saglek Fjord with temporal resolutions ranging from 15 -- 68 years in Nachvak Fjord and 12 -- 49 years in Saglek Fjord. Mass accumulation rate values suggest that the majority of the sediment is accumulating in the center of the basins. Further analyses suggest that: postglacial sedimentation was on average constant in Nachvak Fjord; in Saglek Fjord sediment accumulation was more rapid during the last ∼100 y as compared to post-glacial times; the main sediment source in Saglek fjord is from rivers with extensive catchments that lack glaciers, and in Nachvak fjord from smaller rivers with steep, small and presently glaciated catchments as well as from additional sources such as from the erosion of glaci-marine terraces.