CENOZOIC TECTONICS OF ASIA: GEOLOGICAL OBSERVATIONS AND MODELS

Cenozoic deformation of Asia is dominated by the formation of the India–Asia and Arabia–Asia collision zones and the development of the 4000-km long eastern continental margin. Despite their different onset ages, the two collisional orogens share a similar path of deformation by first experiencing widespread crustal shortening followed by strike-slip and/or normal faulting. Extension along the eastern margin began in the earliest Tertiary, broadly coeval with the onset of the India-Asia collision. Distributed extension there at 65-35 Ma was replaced by localized back-arc spreading at 32–17 Ma. Since 17-15 Ma the eastern margin has been under east–west contraction synchronous with east–west extension in the continental interior across Siberia, North China and Tibet. Continental-margin extension in western Asia started later at 25–20 Ma during a rapid southward retreat of the Hellenic arc. Although the past research has treated the India–Asia and Arabia–Asia collision zones separately, their interactions may have controlled the creation of a 1500-km long zone of northwest-striking right-slip faults and the initiation of the Tian Shan and Altai Shan as Cenozoic intra-continental mountain belts. Cenozoic intra-plate igneous activity correlates in space with Jurassic–Cretaceous magmatic arcs suggesting a causal relationship between the two. The existing geodynamic models on Asia have focused on the driving mechanism of continent-continent collision, the causal relationship between the opening of marginal seas and continental indentation, and the role of thermal evolution in the mantle in controlling stress patterns and thus intra-continental deformation history.