A collaborative team of U.S. and African scientists are acquiring well-constrained paleomagnetic poles from two of the major building blocks of the African continent, the Congo and Kalahari cratons in central and southern Africa (Namibia and Tanzania). Both study areas contain a variety of igneous rocks emplaced 850-700 million years ago, which is a critical time frame in Earth history. During this interval, the ancient supercontinent of Rodinia was beginning to break apart, setting the stage for subsequent rearrangement of continental land masses to form the younger Gondwana supercontinent. The team is carrying out paleomagnetic studies on an extensive suite of samples from selected rock units in the Kalahari and Congo cratons in order to constrain the original relative positions of the two cratons during breakup of Rodinia and prior to assembly of Gondwana. This work is coupled with a detailed program of isotopic dating, designed to produce rigorous constraints on the age of magnetization in the rocks and to determine whether the primary magnetization has been disturbed by subsequent thermal events. The Congo and Kalahari cratons formed the keystone of central Gondwana, which was assembled about 550 million years ago as different parts of the present-day southern continents collided. Acquisition of well-dated poles from both cratons will allow testing of competing models for Gondwana assembly: were the Congo and Kalahari cratons separated by a wide ocean basin before formation of Gondwana or were the two cratons already in roughly their present-day relative positions. The latter scenario would imply that the central part of Gondwana was inherited from the earlier Rodinia supercontinent, about which little is known. The project is collaborative in nature and involves workers at Texas Christian University, Massachusetts Institute of Technology, and the University of Texas at Austin in the US, and at the University of Cape Town in South Africa, the Geological Survey of Namibia, and the University of Dar es Salaam in Tanzania. Students from both the US and Africa are involved in the field and laboratory work.
