Uplift, faulting, seismicity, thermal spring and possible incipient volcanic activity in the Lesotho‐Natal Region, SE Africa: The Quathlamba Hotspot Hypothesis

Abstract

Various features of the Lesotho‐Natal region of south‐eastern Africa, namely, its anomalously high topographic elevation, the occurrence of numerous thermal springs, a few enigmatic CO2 gas exhalation sites, and a significant level of current seismicity in certain zones, suggest that there is some neotectonic activity here. In 1983, there were also media reports of a small volcanic eruption in Lesotho. It has been suggested that a process of continental margin‐parallel warping was in operation during the Plio‐Pleistocene period to produce the apparent uplift and seaward tilting of older geomorphological land‐surfaces, but the fundamental geophysical cause of this process remained unclear. This “cymatogeny” or anorogenic plateau uplift has recently been related to absolute motion of the African continent over the former position of an oceanic spreading ridge but the hotspot reference frame was not used in the absolute motion modelling. As an alternative hypothesis for the Lesotho‐Natal phenomena, the existence of a mantle hotspot near 30°S, 29°E is invoked, its Cenozoic track is modelled, and the ages of a chain of volcanic seamounts in the Mozambique Basin are predicted. The results appear to confirm the self‐consistency of the hotspot frame as a preferred reference system for lithospheric absolute motion.