aus dem MARUM und dem Fachbereich Geowissenschaften der ...

MARIA S. MERIAN-Berichte, Cruise 20, Leg 4, Bridgetown – Freeport, 15.3.2012 – 7.4.2012
6.5.3 Great Bahama Bank Bathymetry and Sub-Seafloor Structures
(Gregor Eberli, Paul Wintersteller, Dierk Hebbeln)
The Great Bahama Bank working area is located about 100 km south of the Bimini Slope area
and includes "AUV Site 1" introduced by Correa et al. (2011). The mound structures in this area
are located on and in between a series of low relief ridges that have a divergent pattern (Fig.
6.25). The mounds are highly variable in size and orientation. The ridges end up slope (to the
east) at a 50 m high step in the slope that can be followed over 10s of kilometres. In contrast to
the Bimini slope area, this working area often exhibits a soft sediment cover (Fig. 6.27).
Fig. 6.27 PARASOUND profile in the upslope position of the Bimini slope working area displaying the dual
system of layered fine-grained sediment partly covering the steep mounds and the hard surface with
solitary individual mounds that are transparent and have diffraction hyperbolas.
As a result many of the mounds in this area have a moat at their base. Nevertheless the
distribution of the mounds is reminiscent of a boulder field that is partly buried by finer-grained
sediment. The depressions in between have a striation perpendicular to the up slope scare while
the sediments are aligned in a N-S direction. This indicates a decoupled depositional process of
the coarse and fine sediments. The coarse fraction is clearly related to down slope mass gravity
flows, while the fine-grained portion is deposited as a contourite.
6.5.4 Great Bahama Bank ROV Observations
(André Freiwald, Lydia Beuck, Claudia Wienberg, Dierk Hebbeln, Nico Nowald,
Götz Ruhland)
Groundtruthing along the slope west of the Great Bahama Bank was performed with six ROV
dives (Fig. 6.25), most of them in the deeper mound area between 700-600 m (GeoB 16366,
16373, 16374, 16381). Two dives surveyed the shallower ridge apron closer to the escarpment,
where an isolated mound pierces out (GeoB 16387, 16388). The emphasis was on deciphering
43