Rodinia and the Precambrian

7.4.1 Rodinia

Geological similarities between the late Proterozoic margins of western North America and eastern Australia (Bell and Jefferson, 1987) led to the hypothesis of the existence of a late Proterozoic supercontinent (Moores, 1991; Dalziel, 1991; Hoffman, 1991b). The proposed reconstruction of this supercontinent is based on geological evidence linking truncated Grenville-aged mobile belts (-1.3-1.1 Ga) on the margins of Laurentia, East Gondwana, Amazonia, and Baltica. The western margin of Laurentia faces East Antarctica in the so-called SWEAT (southwest U.S.A.-East Antarctica) connection (Moores, 1991). This supercontinent has been named Rodinia (McMenamin and McMenamin, 1990) from the Russian word "rodit" meaning "to beget" or "to grow". Rodinia begat all subsequent continents and the continental shelves were the cradle of the earliest shelled animals.

Fig. 7.20. Reconstruction of the Neoproterozoic supercontinent of Rodinia. Grenville-age (-1.3-1.1 Ga) mobile belts are shaded. KA, Kalahari craton, MA, Madagascar. Reproduced with permission from Hoffman (1991b). © American Association for the Advancement of Science.

Over the past decade the reconstruction, evolution, and breakup of Rodinia have become major topics in global tectonics and paleomagnetic data will clearly play a major role in their resolution. The original reconstruction of Hoffman (1991b) also includes Siberia and the separated Kalahari, Congo, and West Africa cratons (Fig. 7.20), although these links are poorly constrained. Based on stratigraphic correlations and tectonic analysis, Li et al. (1995) proposed, in a reconstruction of Rodinia, that the Yangtze block of South China could have been a continental fragment caught between the northeast part of the Australian craton and the northwest part of Laurentia.

The assembly of Rodinia is assumed to have been of Grenville age (-1300-1100 Ma). The timing of its breakup is not known with certainty, but it is generally thought to have been in existence for at least 300 Myr. Therefore, any paleomagnetic test of possible reconstructions of Rodinia involves an analysis of paleomagnetic data in the time range 1100-700 Ma.

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