A multichannel seismic survey was conducted on Lake Turkana, a rift lake occupying a portion of the Eastern Branch of the East African Rift System. This survey revealed the presence of a significant rift structure beneath the lake, the extent and structural details of which had been previously unknown. The lake is underlain by a series of half-graben basins which alternate in polarity along the axis of the lake, and are linked end to end by zones of structural high. These half-graben often have Quaternary volcanic centers located near their latitudinal midpoints. Half-graben basins beneath Turkana deepen progressively to the north, attaining thicknesses of up to 4 km. A deep seismic reflector has been identified, and is believed to correspond to the top of a thick series of Mio-Pliocene flood volcanics. Overlying reflectors are thought to correspond to fluvial, lacustrine and volcano-clastic sediments that are Plio-Pleistocene to Recent in age. The style of rifting beneath Lake Turkana is similar to that observed beneath Lake Tanganyika, which occupies a portion of the Western Branch of the East African Rift System. The most noticeable differences are the abundant volcanism and smaller half-graben size associated with Lake Turkana. These differences may be attributed to the warmer, thinner lithosphere underlying the Eastern Branch as compared to that underlying the Western Branch.
ASJC Scopus subject areas
- Earth-Surface Processes