Lake Tanganyika Blocks

Location

The Tanganyika Graben is part of the grabens of the West Branch of the East African Rift. It is shared between Burundi, the Democratic Republic of Congo, Tanzania and Zambia.

As a whole, the Tanganyika Graben as a sedimentary basin, covers an area of ​​approximately 35,000 km² including 32,500 km² offshore and 2,500 km² onshore (the Ruzizi plain in the North). The area of ​​the Congolese part of Tanganyika Graben is approximately 16,500 km² (~15,500 km² offshore and ~1,000 km² onshore).

Lake Tanganyika, 650 km long, 50 to 80 km wide and having a depth of about 1470 km, is the second African lake by its surface after Lake Victoria. It is fed by two main rivers, the Ruzizi and the Malagarasi. Its waters join the Congo Basin, via the Lukuga River, then the Atlantic Ocean.

Geological and Structural Context

The Lake Tanganyika sedimentary basin has a syn-rift series of at least 6,000 m thickness comprising three sedimentary sequences:

• A Miocene fill consisting of lacustrine clays, turbiditic sands and conglomeratic fans whose thickness is ±5,000m;

• Fluvio-lacustrine sand and silt formations from 500 to 2,000m

• Deltaic sediments with coal and lacustrine clays (300-2000m) from the Permian;

The Karoo formations observable on the surface in the Luama Trough would dip into Lake Tanganyika in the centre.

2D multi-track reflection seismic data show that the geomorphology of the Tanganyika Graben is characterized by a mosaic of 7 asymmetrical sub-basins, rectangular in piano key shape, oriented NNE-SSW to NW-SE.

Structurally, these sub-basins are depocenters grouped into 2 distinct main sections separated by the Kalemie Shoal (Figure 47), (Tiercelin and Mondeguer, 1991):

• North Section consisting of the Bujumbura, Rumonge, Kigoma and Ruzizi Sub-Basins which in turn is separated from the North Section by the Ubwari Shoal;

• Southern Section consisting of the Kalemie, East-Marungu and Moba Sub-Basins.