Abstract The Laurentian Fan is one of the largest submarine fans on the western margin of the North Atlantic. Recently acquired high-resolution multibeam bathymetric data (60 m horizontal resolution) reveal a major mass-transport deposit (MTD) on the Western Levee of Western Valley (WLWV), covering >14 000 km 2 in water depths from 3900 to >5000 m. Typical submarine landslide features are observed such as headscarps that in places reach the crest of the levee, crown cracks, extensional ridges, blocky debris and flow lineations. Multiple headwalls are observed on 3.5 kHz sub-bottom profiles, indicating that the landslide retrogressed upslope. While the upper parts of the MTD consist of intact blocks that were displaced downslope as ridges and troughs, the lower parts exhibit a c. 30 m thick incoherent to transparent acoustic facies, typical of debris flows. Landslide geomorphology therefore suggests that it was generated as a retrogressive spread and that slide blocks disintegrated downslope to become a blocky landslide with a surficial debris flow. The blocky landslide/debris flow extends downslope c. 90 km and partially fills a submarine channel. The superposition of the MTD filling the channel and its location at the top of the stratigraphic succession in the levee suggests that it is late Quaternary in age, possibly Holocene. Deeper seismic reflection data also show that this is a rare event during the Quaternary; it is the largest MTD observed in the upper c. 375 m of the levee succession and among the largest and deepest in the western North Atlantic.

Abstract A surge of exploration activity along the continental slopes offshore of Nova Scotia and Newfoundland has generated significant advances in the understanding of the salt tectonics beneath these regions. Although well control beyond the shelf break is still sparse, extensive coverage by modern 2D seismic data permits definition of five tectono-stratigraphic subprovinces, each with a distinctive salt deformation style related to regional basement morphology and first-order differences in sedimentation. The deformation styles range from halokinetic growth of passive diapirs sourced from a primary salt basin to extensive development of allochthonous canopies seaward of rapid progradation. Thin-skinned extensional and contractional structures are evident throughout the study area.