Geophysical investigations of faults in the Makgadikgadi Basin, northern Botswana

Abstract

The juxtaposition of the Makgadikgadi Basin against the nearby Okavango Delta in northern Botswana has intrigued researchers for decades. The Makgadikgadi Basin forms a vast wasteland marked by two major saltpans that extend over 37,000 km2. These two pans, collectively called the Ntwetwe and Sua, are relics of a giant paleo-Lake Makgadikgadi (PLM) that has been subjected to extensive faulting. While the Okavango Delta has been largely studied, little information exists on the nearby Makgadikgadi Basin. Past studies have speculated that the northeast trending surface faults and active seismicity in the area are linked to the southwest propagation of the East African Rift System (EARS). However, to our knowledge no geophysical/tectonic studies to date confirm this proposition that rifting is occurring in this area. Our Shuttle Radar Topography Mission (SRTM) data combined with our aeromagnetic data indicates that the surface faults do extend into the basement and provide evidence for an extensional setting. Furthermore, we found that the fault-length relationships are quite inconsistent with previous models, and are very young in age as they displace the youngest topographic features dated in the area, the Alab sand dunes (~200,000 B.P.).