Palaeomagnetic constraints on the palaeogeography of China: Implications for Gondwanaland∗

The Appendix [indicated by an asterix (∗) in the text] is a Supplementary Paper lodged with the National Library of Australia (manuscript section); copies may be obtained from the Business Manager, Geological Society of Australia.

Published palaeomagnetic results for China unequivocally show that the three major blocks of China—North and South China Blocks and Tarim—were at or near equatorial latitudes in the Early and Middle Palaeozoic, although they certainly did not have their present relative configuration during that time. These Chinese blocks may have been an ancient equatorial archipelago lying between a northerly Siberia continent and a southerly Gondwanaland continent throughout the Palaeozoic. Palaeomagnetic evidence from Chinese blocks appear not to be consistent in detail with various speculations on rapid true polar wander during Early and Middle Palaeozoic. Late Palaeozoic palaeomagnetic data suggest that the various blocks of China were too far north to have attached to Gondwanaland and suggest that they rifted from Gondwanaland during the Late Devonian and Carboniferous. Studies of Late Permian palaeomagnetic data for the major blocks of China demonstrate major diachronous closures between the Chinese blocks themselves and with Eurasia. They contradict the widely held view that the Central Asian Fold Belt, which runs across North China just north of the 40°N, is the zone where China was sutured to Siberia in Permian time, and suggest a composite Mongolia‐North China plate that became sutured to Siberia in Mesozoic time by anticlockwise relative rotation about a point of initial collision (50°N, 75°E) near the western end of the South Siberian Fold Belt. The westward disappearance of Jurassic marine sediments on the northern margin of the Mongolia‐North China plate indicates that suturing and rotation were essentially complete by the end of the Jurassic. The amalgamation of North and South China appears to have taken place over a similar time span and by a similar but antithetic mechanism, with collision first occurring near the eastern end of the Qinling Fold Belt in the Permo‐Triassic, and suturing progressing westward due to clockwise rotation of South China relative to North China. The accretion of the North and South China Blocks probably was finished in Middle Jurassic, a little earlier than their final suturing with Eurasia. A left‐lateral strike‐slip displacement of 1400 km for Tarim, parallel to the southeast boundary of the Kazakhstan Block, can account for the discrepancy in Early Triassic poles for Tarim and Siberia and there is an indication that Tarim may have moved northeastward with respect to Eurasia even after the Cretaceous as a result of the India‐Eurasia collision. This event appears to have affected a region much larger than the Tibetan plateau, perhaps reaching as far north as the Altai fold belt in Central Asia.

Key words:

• Australia
• China
• Gondwanaland
• palaeogeography
• palaeomagnetism
• Palaeozoic
• Tarim
• tectonics

Notes

The Appendix [indicated by an asterix (∗) in the text] is a Supplementary Paper lodged with the National Library of Australia (manuscript section); copies may be obtained from the Business Manager, Geological Society of Australia.