Paleomagnetism of cretaceous continental redbed formations from Indochina and South China, their Cenozoic tectonic implications: a review

Abstract

Available paleomagnetic data of Cretaceous redbed formations from Indochina and South China blocks are compiled and their tectonic significance is reviewed in a common reference frame of the Eurasian coeval paleopoles. The important factors that play a vital role in determining the tectonic significance of a paleomagnetic result have been taken into consideration and discussed. Review of the Cretaceous paleomagnetic data from the South China block further confirms the conclusion of the previous researchers that the present geographic position of the South China block has been relatively stable with respect to Eurasia since Cretaceous time and shows that the paleomagnetically detected motion of a coherent lithospheric block must be based on the representative data obtained from different places across the block; so the local tectonic movements can be distinguished. Cretaceous paleomagnetic data from the Indochina - Shan Thai block reveal complex intra-plate deformations that have been occurred due to the India - Eurasia collision. Paleomagnetically detected motions from the block-margin areas are mainly reflecting the displacement of upper crustal blocks due to folding and faulting processes, thus a rigid lithospheric block rotation and translation cannot be assumed. The paleomagnetic results from the areas located next to the south of the Red River fault suggest that the fault does not demarcate non-rotated and significantly rotated regions. Accordingly, given the difficulty in separating true lithospheric plate motions from those of superficial crustal blocks, we advocate extreme caution in interpreting the paleomagnetic record in regions such as Indochina where block interaction and strong deformation are known to have occurred.