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

Abstract

Late Cretaceous Chisulryoung Volcanic Formation (CVF) in southeastern Korea contains four ash-flow ignimbrite units (A1, A2, A3, and A4) and three intervening volcano-sedimentary layers (S1, S2, and S3). Reliable U-Pb ages obtained for zircons from the base and top of the CVF were 72.8 ± 1.7 Ma and 67.7 ± 2.1 Ma, respectively. Paleomagnetic analysis on pyroclastic units yielded mean magnetic directions and virtual geomagnetic poles (VGPs) Our best estimates of the paleopoles for A1, A3, and A4 are in remarkable agreement with the reference apparent polar wander path of China in late Cretaceous to early Paleogene, confirming that Korea has been rigidly attached to China (by implication to Eurasia) at least since the Cretaceous. The compiled paleomagnetic data of the Korean Peninsula suggest that the mode of clockwise rotations weakened since the mid-Jurassic. Such interesting variation of vertical rotations in the Korean Peninsula might result from the strike-slip motions of major faults developed in East Asia (the Tancheng-Lujiang fault to the northwest and the Korea-Taiwan strait fault to the southeast), near-field tectonic forcing of the subducting Pacific Plate beneath the Eurasian Plate, and far-field expressions of the India-Asia collision.

Special issue on “Recent advances in environmental magnetism and paleomagnetism”

“…Based on a paleomagnetic study on Miocene sediments from the Oidawara Formation, eastern southwest Japan, Hoshi et al (2015) revealed that clockwise rotation of southwest Japan occurred mainly between 17.5 and 15.8 Ma, at a rotation rate of ~23°/Myr. Furthermore, Jeong et al (2015) presented the tectonic evolution of the Korean Peninsula based on the paleomagnetism and U-Pb geochronology of the late Cretaceous Chisulryoung Volcanic Formation. The weighted mean ages obtained by U-Pb zircon dating from the base and top of the formation are 72.8 ± 1.7 and 67.7 ± 2.1 Ma, respectively.…”

Magnetic Fabrics and Source Implications of Chisulryoung Ignimbrites, South Korea

“…A detailed paleomagnetic analysis of the CVF was reported elsewhere (Jeong et al, 2015), hence, only a new rock magnetic investigation is described here. For sample 27A, the alternatingfield (AF) decays of natural remanent magnetization (NRM) were relatively hard, with median destructive field (MDF) of ∼30 mT ( Figure 4A).…”

“…Member Description Intrusion Gadaeri granite intrusion K/Ar biotite age: 63.9 ± 1.8 Ma (Reedman et al, 1989) 2nd eruptive cycle A4 Welded lithic-rich tuff U/Pb zircon age: 67.7 ± 2.1 Ma (Jeong et al, 2015) Intrusion Cheokwari granodiorite intrusion K/Ar hornblende age: 76.3 ± 11.7 Ma (Reedman et al, 1989) 1st eruptive cycle S3 Tuffaceous sediments…”

“…Welded lapilli tuff U/Pb zircon age: 72.8 ± 1.7 Ma (Jeong et al, 2015) Country rocks S0 Sedimentary rocks (mudstones and sandstones)…”

“…The A4 member is a product of the second eruptive cycle and S3 represents sedimentations during the interval between the two major eruptive cycles (Reedman et al, 1989;Park, 1990). The U/Pb zircon ages of A1 and A4 members are 72.8 ± 1.7 Ma and 67.7 ± 2.1 Ma, respectively (Jeong et al, 2015). The A4 member was intruded by the Gadaeri granite (biotite K/Ar age of 63.9 ± 1.8 Ma; Reedman et al, 1989; Table 1).…”