Preface The expedition ARK XIX/3 with the German icebreaking RV ...

A. 4.3 Sedimentary and hydrodynamic processes and interactions in the "Belgica Mound"
province, Porcupine Seabight
Wheeler, A., Foubert, A., Dorschel, B., Gault, J., Kozachenko, M., Thomsen, L.,
Unnithan, V.
A. 4.3.1 Introduction to the "Belgica Mound" setting
Foubert, A.
The "Belgica mound" province is characterised by conical mounds asymmetrically buried
along the eastern continental margin in the Porcupine Seabight (De Mol et al., 2002; Van
Rooij et al., 2003). Multibeam imagery (Beyer et al., 2003) revealed that this part of the
basin is dominated by surface mounds and some buried mounds, with a north-south
orientation at depths of 500-1000 m. These mounds can rise up to 300 m above the
seabed and can measure up to a few km across. Some mounds are characterised by
depressions at the steep downslope side of the mounds that are probably the result of
strong bottom currents around the mounds (Van Rooij et al., 2003).
De Mol et al. (2002) and Van Rooij et al. (2003) attributed the net south-north alignment
of the coral banks to the presence of eroded ridges of an acoustically transparent unit of
probable Miocene origin. Since corals grow preferentially in elevated locations
(Frederiksen et al., 1992; Freiwald, 2002), the local morphological characteristics make
this site attractive for deep-sea coral settling and growth. In the vicinity of these large
coral mounds, small mounds (the "Moira mounds") exist (Wheeler et al., subm).
As well as these mound structures, a multitude of channels are also observed in the area.
A large, along-slope, north-south to northeast-southwest channel forms the western limit
of the Belgica Mound province. Shallow south-west trending downslope gullies feed into
the north-south channel (Van Rooij et al., 2003). Contourite drift systems dominate the
sedimentological processes in the Belgica Mound area, shaped by the presence of giant
carbonate mounds and channels (Van Rooij et al., 2003). Moreover, high resolution sidescan
sonar imagery in inter-mound areas revealed the presence of extensive sand sheets
with numerous bedforms (sediment waves, barchan dunes, gravel ridges, seabed
striations) indicative of high benthic current strengths and active sediment transport
(Wheeler et al.; 2000; Huvenne et al., 2002).
During this cruise, focus was placed on mound formation processes, mound dynamics
and sediment interactions and biodiversity differences between mounds in the "Belgica
Mound" province. Two dives were carried out with the ROV “Victor 6000” (Fig. A4.3.1-1):
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