Paper No. 9
Presentation Time: 11:00 AM
THE ROLE OF PRE-EXISTING STRUCTURES IN THE EVOLUTION OF THE ALBERTINE AND RHINO GRABENS IN UGANDA AND CONGO
Pre-existing structures play an important role in the evolution of rift systems at local and regional scale by controlling strain localization, transfer, rift segmentation, and termination. The NE-trending Albertine and Rhino grabens in Uganda and Congo represent the northern segment of the Western Branch of the East African Rift System (EARS). It is confined to the Precambrian Kibaran orogenic belt extending between the Tanzanian craton in the east and the Congo craton to the west. Recently acquired high resolution aeromagnetic data from the northern part of the Albertine and Rhino grabens in Uganda was analyzed together with Shuttle Radar Topography Mission (SRTM) Digital Elevation Models (DEM) and Full Tensor Gravity Gradiometry (FTG). The study was aimed at understanding the role of the Precambrian structures in the evolution of the Albertine and Rhino grabens. Our study suggests the following: (1) The NE-extent of the Albertine full-graben is controlled by NE-trending Precambrian fabric and a series of NW-SE faults. The Albertine graben terminates at its northeast-end when it encountered NW-trending Precambrian structures. (2) The transfer zone between the Albertine and Rhino grabens is controlled by NE-trending Precambrian structures which might have facilitated the development of relay ramp faults. (3) Strain localization within the better developed southeast border fault of the Rhino half-graben is facilitated by northeast trending Precambrian structures present in the SE part of the basin compared to its NW part. (4) The Rhino graben is segmented into a narrower ENE-trending half-graben with a better developed NW border fault. This coincides with NNW-trending Precambrian structures oblique to the graben. (5) The Rhino graben terminates to the NE against the Precambrian NW-trending Aswa Shear Zone. Airborne geophysical data together with SRTM remotely provide a growing body of evidence that shows the role of pre-existing structures in controlling strain localization, transfer, segmentation and termination especially in the northern end of the western branch of the EARS.