Assessing the potential of syn-rift sediments for geochronological dating and its implications for the development of Makanjira-Shire basin in south Malawi Rift

Abstract

The Upper Shire River basin, located within the zone of progressive interaction and linkage between the southern Malawi Rift and Shire Rift Zone, East Africa, presents an early-stage rift setting where rapid denudation processes take place and have profound influence on the geomorphological evolution of the region. The basin is key to the understanding of mechanisms involved in propagation and growthin young rifts. Although the tectonics in the region are well studied, lack of age constraints due to well-dated strata poses challenges in the understanding of the timing and mechanisms of rift evolution in this section of the south Malawi Rift. We used syn-rift sediments deposited from the rift shoulders to test the applicability of OSL and radiocarbon dating techniques in a poorly dated data-constrained region of the Malawi Rift. Our results suggest that proper sampling strategy is paramount in using the OSL technique for dating in areas of high dosage such as the one under consideration. However, the technique offers potential for use in these areas. Furthermore, we conclude from these findings that the evolution of the Upper Shire basin was triggered by tectonic movements along the Makongwa scrap that were responsible for redirecting the Likwenu River into the in the Zomba Graben through the Upper Shire at least during the Upper Pleistocene.