Channels and gullies on the continental slope seaward of a cross-shelf trough, Labrador margin, eastern Canada

Abstract

The Labrador Shelf is characterized by several cross-shelf troughs separated by intervening shallower banks. The troughs were probably occupied by fast-flowing ice streams in the Late Pleistocene. Hopedale Saddle trough has a long Quaternary history of till progradation at the shelf edge, and the modern continental slope developed over a major 0.3 Ma shelf-edge failure complex. The upper slope exhibits a series of relatively narrow and deep gullies, whereas the mid-slope contains wider and shallower channels that are locally anastomosing (Fig. 1a). The erosional submarine landforms on the slope are likely to be linked to the delivery of dense sediment-rich meltwater to the shelf edge from a full-glacial ice stream (Piper et al. 2012). Fig. 1. Multibeam bathymetry and seismic profile of gullies and channels on the continental slope in the central Hopedale Saddle region, offshore of Labrador. ( a ) Swath-bathymetric image. Examples of areas of convergent (C) and divergent (D) channel sections are labelled. IL, inner levee; T, incised-thalweg channel. White arrows indicate examples of artefacts. Acquisition system Kongsberg EM300. Frequency 30 kHz. Grid-cell size 10 m. ( b ) Location of study area (red box; map from GEBCO_08). ( c ) Seismic-reflection profile x–x′ across several channels along the mid-slope (located in (a)). VE×17. Acquisition system Sleeve-gun. Frequency 120–850 Hz. MIS, Marine Isotope Stage; GFD, glacigenic debris-flow; H, Heinrich Layer. ( d ) Enlarged oblique …