The southern African Plateau is a unique and particularly intriguing example of a continental plateau, a large elevated interior region of a continent. The causes of plateau elevation gain, both of the southern African plateau and of continental plateaus generally, are not well understood. In this project, recent advances in apatite (U-Th)/He and 4He/3He thermochronometry are used to investigate the erosional history of the southern African plateau. These methods resolve the cooling history of rocks as they move through the upper few kilometers of the Earth's crust, and allow insight into denudation and topographic evolution at the Earth's surface. Erosion, or denudation, is the transport of rock materials at the Earth's surface by a mobile agent, such as water, wind or ice.
There are two major gaps in our knowledge of the erosional history of the southern African Plateau: the denudation history of the elevated plateau itself is poorly constrained, and the post-65 Ma denudation history of both plateau and coastal passive margins is not well known. No apatite (U-Th)/He data has been published for any location in South Africa. The research strategy is specifically designed to capitalize on new methodological advances that broaden the utility of the apatite (U-Th)/He and 4He/3He techniques. Four research questions motivate and will be addressed by the present study: 1) What is the erosional history of the elevated interior of the southern African plateau, and what are its implications for elevation gain of the plateau? 2) Is there a spatial heterogeneity of denudation that mimics the spatial sweep of magmatism, diamondiferous pipe emplacement, and regional heating across the region? 3) Is regional erosion instead attributable to the evolution of river systems in the plateau interior? 4) Is there a phase of accelerated erosion after 65 Ma that could be attributable to a phase of plateau surface uplift?
A comprehensive education component is being carried out. Project personnel are collaborating with the African Earth Observatory Network to run a short course on (U-Th)/He thermochronometry in South Africa as part of African Earth Observatory Network's Africa-wide network plans. There is no (U-Th)/He facility anywhere in Africa. An African student associated with African Earth Observatory Network will be involved in the project and travel to the U.S. to gain hands-on experience with cutting-edge analytical methods. The principal investigator is also participating in the University of Colorado's Science Education Initiative through development, implementation, and evaluation of a modular approach to teaching critical thinking in Earth Science. The research motivations for the proposed South African project will be developed into one of these modules. The effectiveness of the new materials will be assessed at the module and course level with help from a Science Teaching Fellow affiliated with the Colorado's Science Education Initiative.
This project is supported by the Tectonics and Education and Human Resources Programs in the Earth Sciences Division and the Africa, Near East & South Asia Program in NSF's Office of International Science and Engineering.
