The Lower Cretaceous reference pole for North China, and its tectonic implications

Abstract

Summary A palaeomagnetic study of Lower Cretaceous continental sediments from the south‐southwestern part of the Ordos basin, North China block (NCB), has been carried out. Stepwise thermal demagnetization was used to isolate magnetic components. The low‐temperature component is generally removed between 200 °C and 350 °C and corresponds to the Earth's present field direction. A high‐temperature component of magnetization, with two polarities, was defined from 10 sites with D = 16.4°, I = 50.5° (K= 50.8, α95= 6.8°). The corresponding pole position is located at 75.8°N, 208.7°E (dp= 6.1°, dm= 9.1°). This Lower Cretaceous pole compares well with the hairpin loop of the Eurasian synthetic APW path (Besse & Courtillot 1991) that is inferred from the North American, Eurasian, African and Indian plates. The available late Mesozoic palaeomagnetic data from the NCB and adjacent South China block (SCB) are reviewed. Comparison of these data suggests important intraplate deformation: the area to the east of the Tancheng‐Lujiang fault may have undergone local clockwise post‐Cretaceous rotations of 10‐29° relative to the stable western craton of the NCB. The data also indicate that no palaeomagnetically significant eastward movement of the SCB with respect to the NCB and Eurasia occurred after the Cretaceous.

Paleomagnetism indicates no Neogene vertical axis rotations of the northeastern Tibetan Plateau

“…On a more regional scale, concordant paleomagnetic directions are observed in Early Cretaceous rocks of the Ordos Basin [ Sun et al , 2001] and in the North China blocks [ Ma et al , 1993; Chen et al , 2002b]. Early Cretaceous paleomagnetic directions from the Tarim Basin are concordant with results from the Hexi corridor [see Dupont‐Nivet et al , 2002b] and paleomagnetic results from Tertiary red beds in the Qaidam Basin indicate no vertical axis rotation since Oligocene time [ Dupont‐Nivet et al , 2002a].…”

Late Cretaceous palaeomagnetic results from Sikhote Alin, far eastern Russia: tectonic implications for the eastern margin of the Mongolia Block

“…While counterclockwise rotation occurred in the eastern part of the Mongolia Block, the eastern part of the NCB including the Korean peninsula was subjected to clockwise rotation during the Cretaceous (Ma et al 1993; Uchimura et al 1996) (Fig. 7).…”

“…The many blocks comprising Sakhalin experienced a domino style deformation during the subduction of the Pacific Plate (Takeuchi et al 1999). The Korean peninsula and environs have been subjected to clockwise rotational motion with respect to the interior of the Asian continent since the Cretaceous (Ma et al 1993; Zhao et al 1999; Uno 2000). A large northward movement of the eastern part of Asia is implied by palaeomagnetic data from Korea and Japan (Lee et al 1987; Otofuji 1996).…”

Geometric model of conjugate faulting in the Gyeongsang Basin, southeast Korea

“… Doh and Piper [1994] reported 30° post‐Cretaceous clockwise rotation of the Baekunsan syncline outside the northern Gyeongsang Basin, but Kang and Kim [2000a] suggested that this clockwise rotation could be correct if it ended before emplacement of the Bulguksa granitic rocks. Recent paleomagnetic studies report that clockwise rotation of the Korean Peninsula may be associated with post‐Cretaceous clockwise rotation of the eastern block of the Tan‐Lu fault with respected to the North China block [ Ma et al , 1993; Uchimura et al , 1996; Zhao et al , 1999; Uno , 2002; Itoh et al , 2006]; the rotation event seems to have affected the entire Korean Peninsula [ Uno and Chang , 2000; Uno , 2000]. Therefore, our model is not only able to interpret clearly the complexity of geological phenomena in the Gyeongsang Basin but also contributes to constrain the tectonic evolution of East Asia quantitatively.…”