In order to detect a possible clockwise rotation of the Korean Peninsula with respect to the North China Block, Early Triassic rocks in the Ryeongnam Block, Korean Peninsula have been restudied. Sandstones in the Nogam Formation were collected at four sites for palaeomagnetic study. A high-temperature magnetization component with an unblocking temperature of 690 °C is isolated from all sites and yields a positive fold test at the 95 per cent confidence level. This high-temperature component is interpreted to be of primary origin because folding is Middle Triassic in age. The primary directions together with previously reported ones give a new Early Triassic mean direction (D = 347.4°, I = 23.8°, α95 = 5.1°) and corresponding palaeomagnetic pole (62.6°N, 336.1°E, A95 = 4.2°) for the Ryeongnam Block. This improved Early Triassic pole for the Ryeongnam Block is located to the west of the coeval poles for the North China Block. It is therefore concluded that the Ryeongnam Block underwent clockwise rotation of 10° - 15° with respect to the North China Block. Because the amount of rotation observed in the present study is comparable with rotations observed in Cretaceous results from the Ryeongnam Block and in the Triassic-Cretaceous results from other blocks in the Korean Peninsula, the whole of the Korean Peninsula appears to have been subjected to clockwise rotation in Tertiary times.
ASJC Scopus subject areas
- Geochemistry and Petrology