The structural and stratigraphic evolution of Lake Tanganyika: A case study of continental rifting

Abstract Seismic data from Lake Tanganyika indicate a complex tectonic, structural, and stratigraphic history. The Lake Tanganyika rift consists of half-grabens which tend to alternate dip-direction along the strike of the rift. Adjacent half-grabens are separated by distinct ‘accommodation zones’ of strike-slip or scissor motion. These are areas of relatively high basement, and are classified into two distinct forms which depend on the map-view geometry of the border faults on either side of the accommodation zone. One type is the high-relief accommodation zone which is a fault-bounded area of high basement with little subsidence or sediment accumulation. These high-relief areas probably formed very early in the rifting process. The second type is the low-relief accommodation zone which is a large, faulted anticlinal warp with considerable rift sediment accumulated over its axis. These low-relief features continue to develop as rifting progresses. This structural configuration profoundly influences depositional processes in Lake Tanganyika. Not only does structure dictate where discrete basins and depocenters can exist, it also controls the distribution of sedimentary facies within basins, both in space and time. This is because rift shoulder topography controls regional drainage patterns and sediment access into the lake. Large fluvial and deltaic systems tend to enter the rift from the up-dip side of half-grabens or along the rift axis, while fans tend to enter from the border fault side.