THE CONFIGURATION OF ASIA PRIOR TO THE COLLISION OF INDIA - CRETACEOUS PALEOMAGNETIC CONSTRAINTS

Paleomagnetic data from Central Asia show that 1700+/-610 km of shorte ning of southern Asia since Cretaceous time have been absorbed by dist ributed deformation between southern Tibet and the Siberia craton. Thi s result is based on a compilation of Cretaceous poles from the Jungga r, Tarim, Tibet, Indochina, South China, North China, and Mongoha bloc ks, complementing the recent compilation of Enkin et al. (1992a). We p ropose a paleogeographic reconstruction of Asia in the Cretaceous, in which the position of Siberia is derived from the synthetic apparent p olar wander path of Besse and Courtillot (1991). The resulting map, wh ich likely represents Asia as it remained throughout the Cretaceous un til the collision with India began, features an ''unbent'' Tibet, with an east-west trending Andean margin at tropical latitudes and a rathe r continuous belt of continental Ted bed basins extending from Sichuan to Tarim through Tibet. The map allows one to estimate continental sh ortening 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 s uch as that of Avouac (1991).