The Pointe-Du-Fort Mass Movement Deposits, Upper Saguenay Fjord, Canada: A Multiphase Build-Up

The Pointe-du-Fort deposits have been previously interpreted as the result of a single sedimentation event triggered by the 1663 Ms ~7 Charlevoix earthquake. It has been proposed that these deposits represent the spread of a failed mass coming from the south fjord wall. This paper presents multibeam, seismic and CAT-scan imagery evidences revealing that the Pointe-du-Fort deposits are the result of a multiphase build-up which includes many episodes of erosion and sedimentation by debris flows. These processes were induced by bottom slope erosion caused by the passage of a major debris flow coming upstream from the surveyed area, which was previously triggered by the 1663 Ms ~7 earthquake.