Clockwise rotations recorded in Early Cretaceous rocks of South Korea: implications for tectonic affinity between the Korean Peninsula and North China

Abstract

Recent interest has focused on whether South Korea may have undergone variable tectonic rotations since the Cretaceous. In an effort to contribute to the answer to this question, we have completed a palaeomagnetic reconnaissance study of Early Cretaceous sedimentary and igneous rocks from the Kyongsang basin in southeast Korea. Stepwise thermal demagnetization isolated well-defined characteristic magnetization in all samples. The palaeomagnetic directions reveal patterns of increasing amounts of clockwise (CW) rotation with increasing age for Aptian rock units. Palaeomagnetic declinations indicate clockwise vertical-axis rotations of R=34.3°±6.9°for the early Aptian rock unit, R=24.9°±10.6°for the middle Aptian, and R=−0.9°±11.8°for the late Aptian relative to eastern Asia. The new Cretaceous palaeomagnetic data from this study are consistent with the hypothesis that Korea and other major parts of eastern Asia occupied the same relative positions in terms of palaeolatitudes in the Cretaceous. An analysis of and comparison with previously reported palaeomagnetic data corroborates this hypothesis and suggests that much of Korea may have been connected to the North China Block since the early Palaeozoic. A plausible cause of the rotation is the westward subduction of the Kula plate underneath the Asian continent, which is inferred to have occurred during the Cretaceous according to several geological and tectonic analyses.

Paleomagnetism and U-Pb geochronology of the late Cretaceous Chisulryoung Volcanic Formation, Korea: tectonic evolution of the Korean Peninsula

“…A third probable contributor would be far-field expressions of the India-Asia collision (Acton and Gordon 1989;Besse and Courtillot 1991;Vandamme et al 1991;Leech et al 2005). As initially proposed by Zhao et al (1999), the Kula-Eurasia collision may influence the vertical rotations of the Korean Peninsula.…”

“…However, earlier paleomagnetic studies on Mesozoic to Tertiary rocks from the Korean Peninsula showed vertical rotations with respect to China (e.g., Lee et al 1987;Kim and Van der Voo 1990;Doh and Piper 1994;Zhao et al 1994Zhao et al , 1999Doh et al 1999Doh et al , 2002Lee et al 1999;Zhao et al 1999;Uno 2000;Park et al 2003Park et al , 2005Park et al , 2007Kim et al 2009). Then, viable solutions to explain the various degrees of vertical rotations observed in previous paleomagnetic investigations required that individual geologic terranes of the Korean Peninsula formed in Mesozoic to Tertiary experienced different degrees of vertical rotations.…”

“…A robust reconstruction of Laurasia is possible only when Mesozoic paleogeography of the Korean Peninsula is well established, bridging the two sides of the Chinese cratons (e.g., Lee et al 1987;Kim and Van der Voo 1990;Zhao et al 1994Zhao et al , 1999Doh et al 1999Doh et al , 2002Park et al 2003Park et al , 2005Park et al , 2007Kim et al 2009). The primary goal of paleomagnetism is to uncover information about the history of deformation and vertical rotations in geologic units.…”

Paleomagnetic results of the Late Permian Gobangsan Formation, Korean Peninsula: Remagnetization in the southeastern periphery of the Bagjisan Syncline

“…• ; Zhao et al, 1999) is statistically indistinguishable from the remagnetized direction of Cretaceous age (D = 58.8…”

“…On the other hand, the same experiment was newly performed on a sample of primary magnetization from the Doh and Piper, 1994;Doh et al, 1997;Lee et al, 1999;Zhao et al, 1999). Nogam Formation in the central part of the Bagjisan Syncline (Uno, 1999).…”