The configuration of Asia prior to the collision of India: Cretaceous paleomagnetic constraints

Abstract

Paleomagnetic data from Central Asia show that 1700±610 km of shortening of southern Asia since Cretaceous time have been absorbed by distributed deformation between southern Tibet and the Siberia craton. This result is based on a compilation of Cretaceous poles from the Junggar, Tarim, Tibet, Indochina, South China, North China, and Mongolia blocks, complementing the recent compilation of Enkin et al. (1992a). We propose a paleogeographic reconstruction of Asia in the Cretaceous, in which the position of Siberia is derived from the synthetic apparent polar wander path of Besse and Courtillot (1991). The resulting map, which likely represents Asia as it remained throughout the Cretaceous until the collision with India began, features an “unbent” Tibet, with an east‐west trending Andean margin at tropical latitudes and a rather continuous belt of continental red bed basins extending from Sichuan to Tarim through Tibet. The map allows one to estimate continental shortening and rotations between the blocks, which are attributed to the collision. Despite large uncertainties, these have amounts and senses which are in all cases compatible with some recent kinematic models such as that of Avouac (1991). Appendix is available with entire paper on microfiche. Order from American Geophysical Union, 2000 Florida Avenue, N.W.,Washington, DC 20009. Document B93‐007; $2.50. Payment must accompany order.

Late Paleozoic paleogeographic reconstruction of Western Central Asia based upon paleomagnetic data and its geodynamic implications

“…The new estimate of the Late Carboniferous to Early Permian displacement along the Irtysch Fault is significantly different from that of 620km ± 320 km predicted by Wang et al, (2007), because Junggar was considered as a rigid block and an averaged pole from West and South Jungar was used to calculate the displacement along this fault in Wang et al (2007). The consistence of the Cretaceous poles of Mongolia, South Junggar and Siberia (Chen et al, 1993;Hankard et al, 2005) suggests that the bulk of relative motion mentioned above was completed before Cretaceous and possibly Middle Triassic time (Lyons et al, 2002), although Jurassic motions are also described (Allen et al, 1995). Further studies on Triassic rocks around the Junggar Basin will probably provide better age constraints on these events.…”

“…However, the paleomagnetic studies on Mesozoic (especially Cretaceous) rocks show that the relative motions (rotation and latitudinal displacement) are often statistically insignificant (i.e. the mean difference is less than error bar; Chen et al, 1993), implying that the amount of intracontinental deformation remains weak compared to the Paleozoic period.…”

“…However, recent studies have suggested that the displacement between Late Carboniferous and Late Permian interval can reach several hundreds of kilometers in the Chinese North Tian Shan and more than one thousand kilometers in Altai . Wang et al (2007) also considered that the present geometric framework was principally acquired in the Late Permian with only limited Mesozoic motions and a Cenozoic reactivation due to the Indian Collision (Avouac et al, 1993;Chen et al, 1993).…”

Equatorial convergence of India and early Cenozoic climate trends

“…We applied an apparent polar wander synthesis (25) and paleomagnetic data for the Asian blocks (mainly Tibet) (27), in conjunction with a plate kinematic model (28,29), to reconstruct the paleogeographic evolution of India and surrounding continents over the Mesozoic-Cenozoic. India resided in the southern hemisphere for much of the Mesozoic era as part of the Gondwana supercontinent (30), which began to disperse with the opening of the Somali basin during the middle Jurassic (31) and the separation of East Gondwana (which included India, Mada-gascar, Antarctica, and Australia) from West Gondwana (Africa and South America).…”

“…Significantly, the southern margin of Tibet (Eurasia) maintained relatively stable northern hemisphere paleolatitudes all this time, from Ϸ10°N in the Cretaceous (27,37) to Ϸ13°N in the early Cenozoic (37), implying that sediments (4), where peak at Ϸ50 Ma is thought to reflect enhanced chemical weathering during EECO. (C) Changes in paleolatitude of the N-S extent of eventual (light shading) and erupted Deccan Traps (darker shading) as India drifted northward.…”