Seismotectonic range-front segmentation and mountain-belt growth in the Pamir-Alai region, Kyrgyzstan (India-Eurasia collision zone)

The Trans Alai Range along the northern perimeter of the amir region of Kyr gyzstan is at the northern edge of the India-Eurasia collision zone. The ra nge defines a section of Main Pamir thrust, which is divided into eastern, central, and western segments that record differential absorption of plate convergence. The 50-km-long, east-west-striking, central fault segment of t he Main Pamir thrust has dip-slip thrust fault offsets (with a minimum Holo cene dip-slip rate of similar to 6 mm/yr) and is linked to the other segmen ts via northwest-striking dextral transfer. The western transfer faults are well characterized geomorphically, and the westernmost records the predomi nant transition to north-vergent thrusting along the western segment via no rth-vergent, low-angle thrust faults rooted in a steeply south-dipping dext ral shear zone. In contrast, the eastern segment deformation is widely dist ributed and geomorphicalIy less evident, but the transfer also takes place in a structurally complex zone, Asymmetric offset of a regionally correlate d terrace, geomorphic zonation, and the distribution of historic earthquake s suggest that the central segment is mechanically linked with the western segment, but not aith the eastern segment, The progressive closure of the A lai Valley by the northward advance of thrusting exemplifies the annihilati on of an intramontane basin, If the high surface uplift rates implied by th ese geologic observations have been maintained for the last few million yea rs, they attest to the high level of tectonic activity and the recency of c onstruction of the Trans Alai Range.