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Poseidon P342

The research cruise P-342 GALIOMAR with the German research vessel POSEIDON was run from August 19 to September 6, 2006. We have exercised extended sediment-acoustic profiling and have taken 43 sediment cores by vibrocorer and gravity corer.

Return to the cruise-related Project C6.

GALIOMAR (Galicia Ocean Margin Expedition)


Continental shelves are complex and individual sedimentary systems. The understanding of their evolution and their role in sediment filtering, storage and release is of major importance since all land-derived sediments have essentially to cross the continental shelf zone as part of the global sedimentary cycle. The cruise P-342 GALIOMAR to the NW-Iberian shelf was performed to supply an existing RCOM-project with scientific material.

Shallow-acoustic profiling shows surficial mud-belt deposits along the inner shelf and abundant surficial sediment sheets, lenses, patches on its outer parts. These young deposits are separated from each other either by rocky outcrops or by areas of non-deposition, although the outcrops also often cause sediment trapping. Internal stratification of these young depocenters suggests a multi-story depositional history, an observation which is corroborated by the fact that these depocenters do not fully correspond to seafloor mapping of modern mud distribution pattern. Deeper-penetration seismic profiling has elucidated the interplay of massive sediment accumulation units due to high terrigenous sediment supply and tectonic activity plus erosion over longer time periods.

Due to perfect weather condition over major parts of the cruise, we obtained 43 spectacular sediment cores in dense coverage of the study area. This success was made possible by the utilization of a 5-m vibrocorer with a 200-m long electrical cable and by a core-location selection strategy on the basis of Boomer profiles. The retrieved sediment cores show a highly variable inventory of sedimentary facies. Mentioned as some examples, homogeneous mud is related to local depocenters along current-driven sediment pathways. Well-sorted shell gravel horizons indicate the wide occurrence of paleo-coastal remnants, whilst abundant distinct beds of chaotic texture have probably been formed by frequent storm events. These findings evidence a complex depositional shelf history with strong influences through forcing sea-level changes, persistent oceanographic material separation processes and intensive storm modification.

Sedimentological, (organo-) geochemical and geophysical analyses together with a robust stratigraphic control will lead to a reconstruction of the sedimentary history which then will be used to focus on the transport and deposition pattern of individual sediment components.