Abstract

The Tien Shan in Central Asia are the pre-eminent example of intraplate mountain building, and are typically considered an indirect result of the India-Eurasia collision, via the northward indentation of the relatively strong Precambrian lithosphere of the Tarim plate into the relatively weak Paleozoic lithosphere of the Tien Shan region. This hypothesis fails to fully explain the concentration of Tien Shan mountain building along a Tibet-parallel axis, located 500–700 km from Tibet, and also fails to explain the close synchronization of Tien Shan mountain-building events with mountain building in Tibet. I suggest that bending stresses from lithospheric flexure in Central Asia exerted a critical influence on the locus and evolution of the Tien Shan. Models of Paleogene to Middle Miocene flexure indicate that the growth of northeast Tibet may have superimposed a strong bending stress field on the regional stress field. The resultant stress field is characterized by strong topography-normal tensile stress in the Tarim Basin, and an ∼15% increase in compressive stress in the vicinity of the Tien Shan. This stress field severely reduces the likelihood of mountain building south of the Tien Shan, and increases the likelihood of mountain building within the Tien Shan. This result suggests that the generation of bending stresses from lithospheric flexure is a viable and important mechanism for the propagation of stress, and hence deformation, into continental interiors.

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