Gondwana in Early Cambrian times (Groenewald et al., 1991, 1995; Grunow et al., 1996), as is discussed in §7.4.3. Four displaced terranes are recognized as the Antarctic Peninsula, the Ellsworth Mountains-Whitmore Mountains terrane, the Marie Byrd Land terrane and the Thurston Island-Eights Coast terrane. Extensive measurements have been made on the Ferrar dolerites of Middle Jurassic age, first reported by Turnbull (1959) and Bull et al. (1962). Unfortunately these widespread intrusions have remagnetized most of the underlying Mesozoic and late Paleozoic rocks. Despite several attempts to obtain data from this time interval, there has been no success. Therefore, there is a large gap between data from the Jurassic and those from several early Paleozoic rock units (see also Embleton, 1981) as indicated by the dashed line in the APWP shown in Fig. 24a. Phanerozoic paleomagnetic data for East Antarctica are summarized as mean pole positions in Table 6.15.
The Indian subcontinent comprises the main India craton as shown in Fig. 6.22c. North of the Himalayas are two displaced terranes named the Lhasa terrane and the Qiangtang terrane. These terranes accreted to Asia during the Tertiary prior to the arrival of India, as will be discussed further in §7.3.5. The first paleomagnetic measurements from India were reported by Irving (1956) on a few samples of the widespread Deccan Traps of age 67 Ma. It was at once
realized that India must have drifted north a considerable distance during the Tertiary. Many measurements have been made on the Deccan Traps with successive reviews given by McElhinny (1968), Wensink (1973), and Vandamme et al. (1991). The other widely studied formation is the Rajmahal Traps of eastern India of age 116 Ma, results from which were first reported by Clegg et al. (1958). Unfortunately, all the rocks of age between the Cambrian and Late Carboniferous that have been sampled are from the Himalayan region and there is the strong possibility that these rocks have suffered tectonic displacements associated with the collision of India with Asia. Klootwijk and Radhakrishnamurty (1981) reviewed all the data from the Indian subcontinent and included these data in a complex APWP. Following Van der Voo (1993), the more conservative approach is followed here and the data from the Himalayas have been omitted. The mean paleomagnetic pole positions during the Phanerozoic are given in Table 6.16 and the corresponding APWP is illustrated in Fig. 6.24b.
The data from each of the Gondwana continents have strengths and weaknesses, and most of the APWPs are incomplete in some respect or another. These data will be considered again in the context of the reconstruction of Gondwana in §7.2.3, in which a composite APWP is presented based on all the data.
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