Tectonostratigraphy of the northern Okavango Delta and Rift Zone, Botswana

Abstract

The Okavango Rift Zone (ORZ) and Okavango Delta in Northwest Botswana are Earth's youngest continental rift system and largest inland delta. The delta and its underlying sediments record the effects of incipient rifting on the geomorphology and stratigraphy within the (incipient) southwestern arm of the East African Rift System in Botswana. Three open questions that we use river-borne seismic-reflection profile analyses to answer are (1) whether the Gumare fault extends across the delta, (2) whether the Gumare fault zone is a part of the ORZ, and (3) how wide is the ORZ. Our results suggest that the Gumare fault extends across the delta and is a part of the ORZ. Integration of our and pre-existing geophysical data also suggests that the southern section of the ORZ is more active than the northern section that we imaged, and at least 150 km of fault-related extension has occurred within the Okavango Rift Zone. These findings provide constraints on the present-day structural and stratigraphic configuration of the ORZ and OD, which is a fundamental first step towards reconstructing sedimentation and extensional patterns during the earliest stages of continental rifting.