Active faulting and cenozoic tectonics of the Tien Shan, Mongolia, and Baykal Regions

TLDR

Central Asian tectonics feature reverse faulting in the Tien Shan, conjugate strike‑slip systems in the Altai and southern Mongolia, normal faulting in the Baykal rift, and northeast rifting driven by stress analogous to secondary tension in indented plastic materials. The study investigates the active tectonics of central Asia. It interprets Landsat imagery and supplements it with published field observations and seismic data. The authors interpret the observed faulting patterns as resulting from lateral crustal displacements driven by the Indian subcontinent’s penetration, with a smooth transition from thrust to normal faulting reflecting a gradual stress change, and argue that Asia’s intracontinental deformation is better described by continuum deformation than by rigid block motion.

Abstract

We present a study of the active tectonics of central Asia based on an interpretation of Landsat imagery and supplemented with published field observations and seismic data. Reverse faulting dominates the tectonics of the Tien Shan but is associated with prominent northwest trending right lateral strike slip fault systems. Both types of faulting imply approximately north‐south maximum compressive stress. The active tectonics of the Altai and of southern Mongolia are controlled by largescale conjugate strike slip faulting; left lateral on east‐west planes and right lateral on north‐northwest planes. This implies that the maximum compressive stress is oriented approximately northeast‐southwest. Farther north, strike slip faulting gives way to predominantly normal faulting in the Baykal rift system. We interpret all of the active faulting to be a consequence of lateral displacements of the crust caused by the penetration of the Indian subcontinent of Eurasia. We also interpret the gradual change from thrust faulting and high altitudes in the south and west to normal faulting and lower mean elevations in the north and east to reflect a smooth change in the average state of stress. This suggests that the details of the complex intracontinental deformation in Asia are better described by the deformation of a continuum than by the relative motion of a small number of rigid blocks. Intracontinental rifting in the northeast, in particular, may result from a state of stress analogous to the secondary tension that commonly arises within bounded plastic materials indented by a rigid die.