1-54 McCarthy_105-108 van Dijk copy 2013/09/12 10:53 AM Page 1 1 30th Alex L. du Toit Memorial Lecture THE OKAVANGO DELTA AND ITS PLACE IN THE GEOMORPHOLOGICAL EVOLUTION OF SOUTHERN AFRICA T.S. McCARTHY Island vegetation shows a distinct zonation: the outer fringes are characterized by evergreen trees, followed inwards by deciduous trees, ivory palms, shrubs and grass and finally barren soil. The swamp surrounding the island is densely vegetated with sedges and grasses. SOUTH AFRICAN JOURNAL OF GEOLOGY, 2013, VOLUME 116.1 PAGE 1-54 doi:10.2113/gssajg.116.1.1 1-54 McCarthy_105-108 van Dijk copy 2013/09/12 10:53 AM Page 2 30th Alex L. du Toit Memorial Lecture Alex du Toit in the field with his first wife and only son in the early 1900s. Picture by kind courtesy M.C.J. de Wit, E.O. Köstlin and R.S. Liddle Photo: Gevers SOUTH AFRICAN JOURNAL OF GEOLOGY 1-54 McCarthy_105-108 van Dijk copy 2013/09/12 10:53 AM Page 3 T.S. McCARTHY 3 THE OKAVANGO DELTA AND ITS PLACE IN THE GEOMORPHOLOGICAL EVOLUTION OF SOUTHERN AFRICA T.S. McCARTHY School of Geosciences, University of the Witwatersrand, P.O.Box 3, WITS 2050, Johannesburg, South Africa e-mail:
[email protected] © 2013 June Geological Society of South Africa ABSTRACT The Okavango Delta is southern Africa’s largest wetland ecosystem and probably the most pristine large wetland ecosystem in the world. Alex du Toit was the first to recognize the role of faulting in the origin of the Delta, proposing that the Delta lies within a graben structure related to the East African Rift Valley system.