HR: 1340h
AN: T23B-0586    [Abstracts]
TI: Vertical Motions and Drainage Evolution in the Congo River Catchment
AU: * Rogers, E P
EM: elrogers@tcd.ie
AF: Trinity Collge Dublin, Department of Geology, Dublin, 2 Ireland
AU: White, N J
EM: nwhite@esc.cam.ac.uk
AF: University of Cambridge, Department of Earth Science, Bullard Laboratories, Cambridge, CB3 0EZ United Kingdom
AU: Jones, S M
EM: stephen.jones@tcd.ie
AF: Trinity Collge Dublin, Department of Geology, Dublin, 2 Ireland
AB: Africa's large-scale physiographical features are thought to be dynamically supported by mantle convection. The resultant "basin and swell" topography correlates closely with long wavelength free-air gravity anomalies, which can be used as a proxy for the convective pattern. In addition, seismic tomographic studies reveal a region of slow seismic velocity beneath sub-equatorial Africa. This region broadly correlates with a zone of anomalously high elevation, known as the "African Superswell" that stretches from the South Atlantic Ocean across Africa to Afar. Recently, dynamical modelling has been used to predict dynamic topography and uplift rates from the convective pattern inferred by seismic tomography. In this study, high resolution topographic data are used to further constrain spatial and temporal variation of vertical motions in Africa. The Congo Basin is of particular interest as its uplifted southern margin makes up a significant proportion of the catchment. Digital elevation models are used to construct detailed profiles of the rivers that drain Congo basin. River profiles to the north-east of the Congo Basin are concave upwards and appear to have reached equilibrium. In contrast, the elevated region of the southern Congo Basin shows convex upwards river profiles and major knickpoints, indicating that the rivers in this region have not yet reached equilibrium. These knickpoints do not generally correlate with geological boundaries and are more likely the result of a recent change in base level related to mantle convection. By gaining an understanding of the relationship between uplift and surface processes in this region, geomorphology can be used as a further test of uplift rates predicted from seismic tomographic data.
DE: 9305 Africa
DE: 8121 Dynamics, convection currents and mantle plumes
DE: 1815 Erosion and sedimentation
DE: 1625 Geomorphology and weathering (1824, 1886)
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting