The Lake Albert Rift (Uganda) - Sediment Budget, Deformation, Basin and Relief Evolution Since 17 Ma

The measurement of deposited volumes of sediments is based on the basin infilling study which consists on both subsurface data and outcrops analysis. The main objectives were (1) to obtain an age model based on onshore mammals biozones and (2) to reconstruct the 3D architecture of the rift using sequence stratigraphy correlations and seismic data interpretation. Deformation evolution of the rift through times is characterized according to seismic interpretation and to the distribution and quantification of the accommodation for several time intervals. Two major unconformities were identified and dated at 6.2 Ma (Uppermost Miocene) and 2.7 Ma (Pliocene-Pleistocene boundary), coeval with major subsidence and climatic changes.

The landforms analysis is based on the characterization, relative dating and 3D mapping of Ugandan landforms which consist of stepped planation surfaces and incised valleys.

The sediment budget is successful with, between 17 and 2.5 Ma, an excess of 16 % of upstream eroded material compared to the sediment volume deposited that can be explained by the chemical erosion prevailing at this period in Central Africa. The significant (60%) opposite difference between 2.7 and 0 Ma may be the consequence of a high sediment supply resulting from the erosion of the uplifted Ruwenzori Mountains.