Permo-Triassic magnetostratigraphy in China: the type section near Taiyuan, Shanxi Province, North China

Abstract

SUMMARY A palaeomagnetic study has been made of samples collected from the Permo-Triassic type section near Taiyuan, Shanxi Province in the North China Block. No results were obtained from the Upper Carboniferous Shanxi and Taiyuan Formations. Results from the Permian Lower and Upper Shihezi and Shiqianfeng Formations and from the Lower Triassic Liujiagou Formation were restricted mainly to the red shale and red mudstone horizons that were preferentially sampled for this study. After thermal demagnetization, the following pole positions were obtained: Lower Permian (Lower Shihezi Formation, N = 11 samples) 20.9N, 1.4E with dp = 6.1 and dm = 12.2; Upper Permian (combined Upper Shihezi and Shiqianfeng Formations, N = 89 samples) 47.8N, 357.4E with dp = 2.3 and dm = 4.3; Lower Triassic (Liujiagou Formation, N = 25 samples) 50.0°N, 351.OE with dp = 3.7 and dm = 7.0. The sequence crosses the younger boundary of the Permo-Carboniferous reversed (Kiaman) superchron, and the polarity sequence observed suggests that this superchron ended in mid-Ufimian times. A minimum of 13 polarity zones (seven normal and six reverse) then follow before the Permo-Triassic boundary. This is in excellent agreement with currently available observations worldwide.