New Palaeoproterozoic palaeomagnetic data from the Kaapvaal Craton, South Africa
Shawn Letts, Trond H. Torsvik, Susan J. Webb, Lewis D. Ashwal, 2011. "New Palaeoproterozoic palaeomagnetic data from the Kaapvaal Craton, South Africa", The Formation and Evolution of Africa: A Synopsis of 3.8 Ga of Earth History, D. J. J. Van Hinsbergen, S. J. H. Buiter, T. H. Torsvik, C. Gaina, S. J. Webb
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Palaeomagnetic data from the well-dated 2060.6±0.5 Ma Phalaborwa Complex in South Africa (Kaapvaal Craton) are of excellent quality. High unblocking components are carried by magnetite and single polarity remanence directions (mean declination 5.0°, inclination 57.3°, α95 = 5.2°) yield a palaeomagnetic pole (latitude 27.7°N, longitude 35.8°E, A95 = 6.6°) that overlaps with existing poles from the near coeval 2054.4±1.3 Ma Bushveld Complex. The Phalaborwa and Bushveld complex poles, along with poles from the well-dated Vredefort impact (2023±4 Ma) and Post-Waterberg Dolerites (1874.6±3.9 Ma), define the most reliable poles for the Kaapvaal Craton during this time interval (c. 2060–1875 Ma) and witness low rates of Mid-Palaeoproterozoic apparent polar wander. Poorly dated NE–NNE-trending dyke swarms that intrude the Phalaborwa and Bushveld complexes both yield dual-polarity remanence components that share a common mean at the 95% confidence level. Primary palaeomagnetic poles (Phalaborwa dykes pole latitude 7.6°, longitude 12.1°, A95 = 11.8°; Bushveld dykes pole latitude 12.6°, longitude 24.1°, A95 = 10.8°) suggest that they are of the same age as the Post-Waterberg dolerites (c. 1875 Ma). They could also be as old as the Phalaborwa and Bushveld Complexes, however; high-precision geochronology is required to resolve this issue and to enlarge the number of Palaeoproterozoic key poles for the Kaapvaal Craton.
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The African continent preserves a long geological record that covers almost 75% of Earth’s history. The Pan-Africanorogeny (c.600–500—Ma) brought together old continental kernels (West Africa, Congo, Kalahari and Tanzania) to form Gondwana and subsequently the supercontinent Pangaea by the late Palaeozoic. The break-up of Pangaea since the Jurassic and Cretaceous, primarily through opening of the Central Atlantic, Indian, and South Atlantic oceans, in combination with the complicated subduction history to the north, gradually shaped the African continent.
This volume contains 18 contributions that discuss the geology of Africa from the Archaean to the present day. It celebrates African geology in two ways: first, it highlights multidisciplinary Earth science research by viewing the formation and evolution of Africa from 18 different angles; second, it celebrates the work of Kevin Burke and Lewis Ashwal and portrays the wide range of interests and research angles that have characterized these two scientists throughout their careers, working in Africa, and studying African geology.