The overall objective is to determine how sediment is transported from continental and island margins to the deep-sea, including the frequency, magnitude and causes of downslope mass wasting. The study area lies in the eastern North Atlantic from Portugal to south of the Canary Islands, and includes the following distinct continental margin types:
1) a broad passive margin with a gentle continental slope; 2) oceanic islands with very steep slopes and periodic volcanic activity; and
3) a margin with a steep continental slope dissected by large canyons. This third area also contains an oceanic plate boundary characterised by large earthquakes.
Our plan is to make seafloor sediment maps using GLORIA sidescan sonar, improve on detail in small areas with TOBI (high resolution sidescan), integrate these data with subseabed seismic profiles and then sample selected targets to "groundtruth" our geophysical interpretations. In the laboratory, precise dates will be determined for the major events, flow characteristics will be calculated from sedimentary parameters, and mineralogy will be used to tie flow deposits to source areas. In situ pore pressure measurements will determine the current stability of potential future sediment failures. Specific objectives include:
- Mapping of sediment facies throughout the study area and interpretation of the reasons for the distribution of each facies type.
- Assessment of the contributions of mass-wasting, along-slope (contour-current) sediment transport and pelagic sedimentation to overall continental margin evolution. Calculation of the total budget for material transported from the shelf to deep sea and an assessment of its variation through the late Quaternary.
- Determination of the relative importance of debris flows and megaturbidites in mass wasting events on the margin and the relationship between these two transport mechanisms.
- Assessment of the triggering mechanisms of mass wasting including the contributions of sealevel change, seismic activity and volcanic activity on oceanic islands.
- Determination of the role of submarine canyons in sediment transport on continental margins and analysis of the sandy fan-like bodies at the mouths of the canyons.
- Determination of the stability of sediment bodies in different slope environments and identification of areas likely to fail in the future.
- Development of conceptual models to explain sediment erosion, transport and accumulation throughout the study area.
Funding SchemeCSC - Cost-sharing contracts
2000 AD Haarlem
CF1 3YE Cardiff