Fault system at the southeastern boundary of the Okavango Rift, Botswana

Abstract

The seismically active Okavango Rift in northwestern Botswana is probably the southern extension of the East Africa Rift System. Relief is low and many of the geomorphic features of the incipient rift are subtle. The northeast-southwest trending Kunyere and Thamalakane Faults form the southeastern boundary of the rift. Proterozoic structural fabrics of similar trend, belonging to the Ghanzi-Chobe Belt, control the regional trend of the primary Cenozoic fault set of the rift. Geophysical evidence indicates that these are dominantly normal faults forming boundaries to northeast-southwest trending strips of horsts, grabens and half grabens. Two other major sets trend northwest-southeast and north-south. The northwest-southeast set occurs within the interfault strips of the major northeast-southwest trending faults. The latter act as local transfer faults forming boundaries to stress domains within which the secondary northwest-southeast trending faults are produced. Remote sensing imagery shows a weakly developed north-south set that is spatially associated with, and truncated by the northwest-southeast set. The whole fault system probably produces predominantly dip-slip displacements on multiple fault sets responding to a subcontinental east- west extension.