Abstract
We report paleomagnetic results from the Zhepure Shan Formation and the Youxia Formation of the Tingri section (28°42′N/86°43′E) and the Longjiang section (28°27′N/86°40′E) in southern Tibet. A lower coercive component demagnetized below 30 mT and a higher coercive component demagnetized between 30 mT and 100 mT were separated. Rockmagnetic analyses reveal magnetite as the remanence carrier. The differences in coercivity are probably due to a wider grain size spectrum and therefore different domain states. Remanence directions of the low-coercive component are highly scattered and were not considered for further analysis. Directions of the high coercive component of Members A–C of the Zhepure Shan Fm are fairly well grouped within sites (k > 8 for most sites) whereas those of Member D and the overlying Youxia Fm are highly dispersed. Applied fold tests indicate a postfolding remanence for Members A–C. The latest possible time for remanence acquisition of Members A–C is constrained to a mean of 48 Ma by comparing the determined paleolatitudes to the curve of expected paleolatitudes versus age, calculated from the APWP of India. Deformation of the rocks is likely related to India–Asia collision and therefore the remanence age yields a constraint on the latest possible age of the India–Asia collision. In consideration of an extended pre-collisional northern Indian margin (Greater India) the determined values of 48 Ma (mean) and 37 Ma (youngest possible age within 95% confidence limits) underestimate the age of the continental collision.
Published Version
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