REMOTE SENSING BASED STRUCTURAL MAPPING OF THE SOUTHWESTWARD DIVERTED EXTENSION OF THE WESTERN BRANCH OF THE EAST AFRICAN RIFT SYSTEM

This work uses remote sensing and geophysical analyses to characterize the crustal structures of the extensional depressions that divert from the Western Branch of the East African Rift System (EARS) and advance southwestward into the Precambrian Bangweulu cratonic block, the Lufilian arc (fold and thrust belt in the southwest and foreland basin to the northeast), and the Kibaran orogenic belt. It focuses on characterizing the spatial relationship between the complex array of Mesozoic-Cenozoic grabens and the underlying Precambrian structures. To delineate these structures, Shuttle Radar Topography Mission-Digital Elevation Model (SRTM-DEM) was enhanced by applying different filters that allowed for the creation of structural maps and geological cross-sections. Additionally, the World Gravity Model 2012 (WGM 2012) has been used to image the Moho depth. Results of this work revealed that the Southwestern Branch of the EARS extends as dominantly asymmetrical grabens and half-grabens into the Precambrian terranes. These segments include from northwest to southeast the NE-trending Upemba graben, the triangular-shaped Kundelungu depression, the NNE-trending Mweru graben, and the triangular-shaped Mweru-Wantipa graben system. The Upemba graben extends within the Kibaran orogenic belt whereas the Mweru graben is confined to the eastern part of the Lufilian foreland basin on the western side of the Bangweulu Block. The Kundelungu depression is bordered by the Kundelungu plateau in the east, the Lufilian fold and thrust belt in the southwest, and the Kibaran orogenic belt to the northwest. The Mweru-Wantipa graben system extends into the Bangweulu cratonic block as a series of SW-trending asymmetrical grabens and half-grabens. This suggests that at least one segment of the Southwestern Branch extends within a cratonic lithosphere. The Moho map shows that the crust is thicker beneath the Bangweulu cratonic block reaching up to 40 km and it is relatively thinner beneath the Lufilian arc and the Kibaran orogenic belt reaching 30 km. This work supports the notion that rifts generally extend within orogenic belts. It also shows that some can extend into the margins of cratons. Therefore, it is possible that the Mweru-Wantipa graben system is propagating within a zone of lithospheric weakness within the Bangweulu cratonic block.