Palaeolatitude and Relative Position of South-West Japan and Korea in the Cretaceous

Abstract

All the palaeomagnetic results in south-west Japan were classified into three age groupings, namely, Cretaceous, Palaeogene-Miocene and Pliocene-Pleistocene, and an attempt was made to calculate the mean virtual pole position for each age group. From the pole position thus obtained the palaeolatitude at about the centre of south-west Japan was estimated for each age to be 41", 36" and 30" north.On the other hand, the mean virtual pole position for the Cretaceous was also calculated from palaeomagnetic results from Korea, and the palaeolatitude of Korea in the Cretaceous was estimated to be 37 degree north at about the centre of the Korean sampling sites. This value is almost 4 degrees less than the Cretaceous latitude at the centre of south-west Japan.Comparing the difference between the Cretaceous latitude and the present one at the centre of south-west Japan and that at the centre of Korean sampling sites, it can be concluded that south-west Japan has possibly drifted southward and, as the result of this drift, the Japan Sea has been expanded.

Strike–slip fault tectonics and basin formation during the Cretaceous in the Korean Peninsula

“…Lee et al (1987) and Filatova (1990) suggest that the Korean Peninsula, including the Katasiatic plate (continental microplates and blocks within oceanic plates), occupied its modern position during Late Jurassic–Early Cretaceous time. Paleogeographic and environmental reconstruction suggests that the paleolatitude of the Korean Peninsula has been fixed since the Cretaceous (Yaskawa 1975; Smith & Briden 1977), and that the Korean Peninsula was located at 40°N where semi‐arid or arid climatic zones were formed (Woo et al 1991, 1992; Paik & Lee 1994, 1995).…”

Timing of Rotational Motion of Southwest Japan Inferred from Paleomagnetism of the Setouchi Miocene Series

“…The past paleomagnetic studies done before 1970's have already revealed that remanent magnetization of the Cretaceous and Paleogene rocks in Southwest Japan shows significant declination shift relative to those in Northeast Japan (KAWAI et al, 1961;1971), and to those in the Korean Peninsula (YASKAWA, 1975). The pioneer workers suggested that the declination shift was caused by a clockwise rotation of Southwest Japan.…”

Paleomagnetism of the Akiyoshi limestone. Evidence for secondary magnetization.

“…The coincident directions are also identical with the well-known paleomagnetic direction for Southwest Japan before about 15 Ma rather than after about 15 Ma, when This correspondence suggests that the remagnetization occurred before about 15 Ma. YASKAWA (1975) and ITO and TOKIEDA (1986) compiled many paleomagnetic results in Southwest Japan from several authors. Although both compilations contain the results of rocks distributed in the vicinity of the Akiyoshi Plateau, there are no available data to further define the timing of remagnetization.…”