Chapter 2. Tectonics, Climate and Sedimentation in the Albertine Rift

Abstract

The tectonically active early continental Albertine Rift basins are dynamic entities, constantly evolving through time. Periods of crustal extension cause rift valley floor subsidence to create accommodation space and accumulate sediment in basinal depositional centres (‘depocentres’). Periods when stress fields change across a rift can move the maximum rupture along main rift bounding faults to shift depocentre locations over time, often producing a series of syn-rift phases in basin development. In the Albertine Rift, the Lake Edward basin displays superb structural geomorphology that, in this study, could be mapped across the whole width of the rift valley. Often cited in the literature as a classic asymmetric half-graben, it is now clear that this basin is undergoing a change in rift phase, developing into an extremely asymmetric graben with a faulted eastern flexural arch. Tectonics does not operate alone, but forms a coupled dynamo with climate, that together drive and control the sedimentary fill of an early continental rift basin. The theoretical effects of this are modelled for Lake Edward to indicate basinal deposition when tectonics and climate are in, and out, of phase. Finally, the ‘sedimentary geodynamic elements’ that might be expected to characterise early continental rift basins are outlined.