Deglacial landform assemblage records fast-flow and retreat, Inner Hebrides, Scotland

High-resolution bathymetric data have been central to recent
advances in the understanding of past dynamics of the former
British–Irish Ice Sheet (BIIS). As approximately two-thirds of
the former BIIS was probably marine-based during the Last Glacial
Maximum (LGM) (c. 29–23 ka), geomorphic observations
of the seabed are required increasingly to understand the extent,
pattern and timing of past glaciation. Until recently, glacial reconstructions
for the Inner Hebrides, offshore of western Scotland,
have been based primarily on terrestrial observations. Previous
workers have proposed generalized reconstructions in which the
Inner Hebrides are located within a significant former ice-sheet
flow pathway that drained the western Scottish sector of the BIIS,
feeding the Barra Fan during the LGM and earlier glaciations
(Fig. 1). Results from numerical ice-sheet modelling suggest that
former ice-flow velocities within the region were on the order of
hundreds to thousands of metres per year, but yield further insight
by demonstrating how dynamic binge/purge cycles may have
affected ice-sheet mass balance over time (Hubbard et al. 2009).
Following the LGM, ice-sheet retreat through the area is estimated
to have been in the order of 20 m per year (Clark et al. 2012). Here
we present swath-bathymetric data from the Inner Hebrides that
provide in situ constraints on ice-sheet flow and subsequent retreat
dynamics from within this important sector of the BIIS.