Scientific questions

Back to SD2

Certain shelves can be regarded as ‘end member’ systems controlled by a reduced number of external factors; In such settings, sediment budgeting is facilitated.
An accurate balance of clastic shelf sediment volumes is far from trivial because of (1) the open character of such a system in terms of its sediment fluxes and (2) high local variability of the driving oceanographic and sedimentary parameters. However, their calculation should be possible where a limited number of parameters dominate the sedimentary processes in such a system. The three selected study areas chosen represent characteristic end-member shelf types. To get an estimate of how much material is retained or released by an individual shelf system we will combine information provided by the internal architecture (shallow-acoustics and coring) and by the most continuous archives available (in mudbelts, at the upper slope, in canyon systems). Dimensions of depositional units will be characterized by their geometry in concert with a robust age control, and their composition by granulometric, element/geochemical and mineralogical fingerprinting.


Self-organisation of classical siliciclastic shelves can be caused to a considerable extent by the activity and the products of carbonate-secreting organisms.
Most former studies on siliciclastic shelf systems concentrated on the material fluxes from the hinterland and their passage to areas of deposition. However, in-situ carbonate production can modify the sediment dynamics also on siliciclastic shelves by trapping and baffling of sediment, by creating bioherms and by changing grain size spectra. Loci and type of production depend on ecosystems and biological players, and potentially alter the sedimentary profile and architecture. This influence of carbonate components on siliciclastic shelves is far from being fully understood. This project will test the hypothesis that biological activity influences the architecture of clastic shelves, including the locus of breaks and drop-offs in the depositional profile, and the spacing and morphology of sediment transport channels, by feed-back mecha¬nisms between physical and biological processes. This will be achieved by quantifying the extent of areas influenced by carbonate secreting communities on the selected siliciclastic shelves by geophysical methods and by sedimentological examination of surface and core samples.


Aspects of self-organization steer the production, (re-)distribution and consolidation of shelf sediments at shorter scales and influence long-term influx-output budgets.
Although external forces determine general shelf architecture, internal processes should contribute strongly to sedimentation patterns. Production, transport, preservation and remobilization processes interact in controlling sediment fluxes within clastic shelf systems and should be significant for smaller-scale variability. Every sediment deposition modifies shelf topography and currents which in turn locally affects accumulation conditions and patterns. In addition, early diagenetic carbonate dissolution and authigenic clay and iron mineral formation have influence on the long-term influx-output budget of clastic shelves. To assess their vertical and horizontal signatures and effects, we will combine sedimentological, (organo-)geochemical and rock magnetic analyses of box core sections with sub-meter resolution benthic profiling using sonographic methods and our multi-sensor platform GEM Shark.


Methodological strategy
•Subbottom acoustic profiling of sedimentary units and calibration with sediment samples
•Densely-spaced coring on shelf and slope to assess lateral and temporal variability
•Volume estimation from a combination of seismoacoustic and core-based stratigraphy
•Mapping of modern sediment export routes by EM, MS and CTD benthic profiling.
•Sediment-based study of carbonate producers, ecosystems, fluxes and grain-sizes
•Geochemical, physical properties and rock magnetic studies of early diagenetic processes


Project-embedded cruises
Meteor 78-3a (Uruguay/Argentine June 2009)
MSMerian PHAETON (Mauritania Nov 2010)
Poseidon GALIOMAR III (NW-Iberia, June 2011)