A journey through geological time in Namibia (lecture)

Dr Jim MacDonald, University of Glasgow

Namibia, the second largest country in Southern Africa, has a population of only about 2¼ million. Half the land is desert, the Namib Desert on the coast and inland the Kalahari which stretches to the east into Botswana. Much of the rest of the country is scrub punctuated by rocky outcrops – a great place for the study of Geology. This 2,500 km long trek documents episodes in the geological history of Namibia from Mesoproterozoic times to the present day. We will visit the Fish River Canyon, second deepest on Earth, where the metamorphosed rocks of the Namaqualand Complex are succeeded unconformably by the Namibian succession ranging in age from 1000 Ma to Cambrian by which time the supercontinent of Gondwanaland had been assembled. Travelling northwards a landscape dominated by the Great Escarpment bears witness to the dominance of terrestrial erosion throughout much of the Phanerozoic Eon. At the Giant’s Playground huge residual boulders represent what remains of a once more widespread cover of Karoo dolerite. We will climb the largest sand dunes in the world in the Namibian Desert on our way to Walvis Bay on the west coast. Farther north in Damaraland, Brandberg Mountain forms the remains of a huge central volcano active at about 130 Ma at the end of the activity of the Etendeka flood basalts that marked the opening of the South Atlantic and the beginning of the separation of Africa and South America. Much of Damaraland is dominated by the deposition of sedimentary rocks during the Tertiary. These have been subjected to episodes of desert conditions alternating with intense fluvial erosion to produce a landscape resembling that of the American Southwest. Here the culture of the local Damara tribe is preserved in rock art and in a living museum hidden among spectacular outcrops of syenite. Finally we reach the Etosha National Park on the northern margin of the Etosha Pan, a vast expanse of evaporites margined on its southern edge by a series of water holes that sustain an impressive fauna including great herds of zebra, antelopes, ostriches and elephants, prides of lions and many other species.