"Symbols and method of averaging are as given in Table 6.5.

"Symbols and method of averaging are as given in Table 6.5.

the separation of Australia from Antarctica and its northward drift to the present position. For many years it was thought that the pole position had remained essentially fixed through the Mesozoic (McElhinny, 1973a), but more detailed studies have shown that there is fine structure (Schmidt, 1977; Embleton, 1981).

There is rapid polar movement with respect to Australia during the Carboniferous, followed by distinctive movement during the Devonian, which has been carefully delineated by Chen et al. (1995). A large polar shift of about 90° occurs between the Late Ordovician/Silurian and Early Devonian. However, each of these poles is based on a single result and so the shift is not well constrained. This part of the APWP is therefore shown as a dashed line in Fig. 6.23. Although three mean pole positions have been calculated through the Cambrian, the associated errors in the case of the Early and Middle Cambrian means are large. Many of these data are more than 25 years old and the dating of the rocks is often not known as well as authors have suggested.

Antarctica consists of the main East Antarctica craton, whose extent is mostly inferred from coastal exposures (Fig. 6.22b). However, the Coats Land-Maudheim-Grunehogna (CMG) Province in the western part of this craton was formerly an eastern part of the Kalahari craton of Africa prior to the formation of

Was this article helpful?

0 0

Post a comment