Paleomagnetism and tectonics of the Southern Tarim Basin, northwestern China

Abstract

We report Late Carboniferous, Permian, and early Tertiary paleomagnetic data from the southern Tarim basin. Prefolding magnetizations were isolated in each case. The Late Carboniferous–Permian and early Tertiary poles lie at 64.6°N, 166.5°E, A95 = 6.3° and 58.1°N, 202.0°E, A95 = 12.7°, respectively. The Late Jurassic to early Tertiary (J3–E1) paleolatitudes of Tarim and several basins throughout central Asia are similar, yet significantly (10° to 20°) shallower than those predicted by the Eurasian apparent polar wander path. Resolving this discrepancy remains a major problem in Asian paleomagnetism. Discordance of the late Paleozoic poles from Tarim and Siberia suggest that Tarim has rotated about 30° counterclockwise with respect to Siberia since the Permian. Where paleomagnetic samples of both Late Carboniferous to Early Triassic (C3–T1) and J3–E1 ages were collected from the same area of Tarim, a great circle passes through the means of the poles and the sampling locality. This suggests that (1) only a difference in inclination (and not declination) distinguishes the two data sets, and (2) vertical axis block rotations of the C3–E1 strata occurred after E1. Although based on data of lesser quality, the mean Early to Middle Jurassic (J1–2) pole from Tarim differs significantly from the Eurasian reference pole, requiring radical tectonic solutions to resolve them. The Tarim J1–2 pole is indistinguishable from both the mean J3–E1 and C3–T1 poles. The similarity of all the poles and the analogous tectonic setting of present‐day central Asia to that of the late Paleozoic in eastern North America raises the question whether all the data from Tarim are overprinted.

Collision of the Kronotskiy arc at the NE Eurasia margin and structural evolution of the Kamchatka–Aleutian junction

“…This contradicts paleomagnetic data, which indicate a location of the arc some 1,300-1,500 km south of Kamchatka in the Bartonian and Lutetian (Levashova et al 2000a, b). Similar discrepancies between geological and paleomagnetic data in Tertiary formations were documented in many regions over the world, as magnetic inclinations both in sedimentary and volcanic rocks are found up to 20°s hallower than can be expected (Westphal et al 1986(Westphal et al , 1993Gilder et al 1996;Cogne et al 1999). Undetected intra-plate movements, poorly constrained reference poles, a nonaxial magnetic field, and a non-dipolar magnetic field were discussed as possible explanations of this phenomenon, but its nature still remains rather unclear (Westphal 1993).…”

Paleomagnetic constraints on neotectonic deformation in the Kashi depression of the western Tarim Basin, NW China

“…The different tectonic units comprising Tarim also appear to have undergone little or no relative motions during the neotectonic era. In contrast, local rotations of Cenozoic rocks are observed from both the southern and northern margins of Tarim (Gilder et al 1996;Charreau et al 2006;Huang et al 2006b) and are also suggested from study of the Mazatagh Range in central Tarim (Dupont-Nivet et al 2002).…”

“…N number of sites or paleomagnetic poles, k, u latitude and longitude for the paleomagnetic pole, A 95 radius of circle of 95% confidence limit about paleomagnetic pole, R E , R N , R T indicate vertical-axis rotation (?/-counterclockwise/clockwise) with respect to Eurasia, North China, and Tarim-Turfan, respectively (Gilder et al 1996), from Mazatagh in central Tarim (DupontNivet et al 2002), and from the Tuoyun Basin within the Tian Shan close to the TFF (Fig. 1b, Huang et al 2005a).…”

“…Counterclockwise (CCW) rotation of Tarim in the late Paleozoic and ensuing collision between the Altaids and Tarim seem to have played an important role in the formation of a continuous marginal arc south of Tarim (the Silk Road Arc) by terrane emplacement (Natal'in and Sengör 2005;Van der Voo et al 2006). Following collision with the Altaids, the Tarim Block seems to have behaved as a quasistationary paleogeographic unit during most of the Mesozoic and Cenozoic since post-Permo-Carboniferous to Jurassic paleomagnetic poles identify little or no apparent polar wander (APW) (Gilder et al 1996(Gilder et al , 2008. The latter authors attribute the quasi-static behavior of Tarim to compensation of northward motion by an episode of true polar wander identified by Besse and Courtillot (2002) with similar magnitude but opposite direction.…”

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

“…between NCB and SCB was completed by the middle Jurassic as their paleopoles are overlapping each other (Huang and Opdyke 1991;Gilder et al 1996;Gilder and Courtillot 1997). If the Korean Peninsula was exposed to constant tectonic forcing rather than episodic tectonic processes since the Jurassic, then a linear variation of vertical rotation is expected.…”