Professor Nicky White

Vertical Motions, River Drainage and Mantle Convection

It is generally accepted that convective currents within the Earth's mantle drive plate motion. However, despite theoretical and observational advances, our understanding of the spatial and temporal evolution of these currents remains fragmentary. The Earth's stratigraphic record is a potentially rich source of information about this process since convective upwelling and downwelling should produce measurable vertical displacements at the surface. These displacements should influence drainage patterns and the redistribution of sediment: the challenge is to extract useful and accurate constraints. To date, we have concentrated on the fringes of the North Atlantic Ocean whose stratigraphic evolution has been moderated by convective upwelling beneath Iceland over the last 60 million years. Our results allow us to map the planform of upwelling through time. We have also begun to analyze Africa where many significant geological features are thought to be maintained by the convective pattern. Africa is drained by a small number of large rivers whose long-term sedimentary fluxes are primarily controlled by catchment size and relief. Changing flux patterns may help to measure temporal and spatial changes in upwelling and downwelling. The geometry of coastal shelves is particularly sensitive to modest displacements. Measurements of denudation along the West African shelf have been used to reconstruct Neogene vertical motions. These results have commercial application and we have close and fruitful links with the hydrocarbon industry.

Current research projects:

• Constraining uplift and denudation at continental margins by joint inverse modelling
• The relationship between the solid flux at river mouths and catchment and river slope evolution
• The evolution of the Iceland Plume and its oceanographic and stratigraphic consequences
• The structure of the mantle under the British Isles from teleseismic receiver functions
• Quantifying the strain rate evolution and thermal risk at deep-water continental margins.