Geomorphic Landforms and Tectonism Along the Eastern Margin of the Okavango Rift Zone, North Western Botswana as Deduced from Geophysical Data in the Area

Abstract

The location, orientation, and evolution of normal faults that form during continental rifting exert a strong influence on the development of regional features (geomorphology, drainage patterns, basin location, stratigraphy, location of magmatism, and if the process of continental rifting is successful, the geometry of the passive margin) of the rift. Understanding the factors which control the growth and propagation of normal faults at the earliest stages of continental rifting will lead to a better overall understanding of the processes which control the development of continental rifts – an essential component of the plate tectonics paradigm. There are only a few examples of young continental rifts which are suitable for the investigation of the process of border fault development and evolution. The Okavango Rift Zone (ORZ), in northwestern part of Botswana (Fig. 1) is one example of a zone of incipient continental rifting (Scholz et al., 1976; Modisi et al., 2000). Recent studies suggest that faults associated with this rift are still in a juvenile stage (Kinabo et al., 2007), therefore the ORZ provides us with a unique opportunity to investigate the earliest developmental stages of continental rifts such as fault growth and propagation. In areas where the faults are mostly buried beneath large accumulations of sediment, have subdued surface relief, and or where access and travel is limited, as is the case in the ORZ (Kinabo et al., 2007; Modisi et al., 2000), it is difficult to accomplish structural mapping of such areas. For these areas, important structural information regarding rift processes can be obtained from magnetic data (Modisi et al. 2000; Grauch, 2000). Other studies including Chen and Lee (1982); Kervyn et al., (2006) have also shown the utility of Digital Elevation Models (DEM) to map rift fault morphology. In this study, high resolution aeromagnetic (HRAM) data (which provide information about the faulting within the basement) has been used together with SRTM DEM data (which provide surface morphological expression of the faults) to provide a clear perspective of faults and fault patterns associated with ORZ. The information from these sources (HRAM and SRTM DEM) is used to examine stages of fault growth, linkage, and propagation within the ORZ.