Late-Cenozoic tectonic versus glacial control on the topographic evolution of the Terskey Range, Kyrgyz Tian Shan

The relative influence of tectonics and climate on topography and surface processes remains poorly constrained in many mountainous regions. The effect of late-Cenozoic glaciations on global erosion rates and relief is particularly disputed. The Terskey Range, in the Kyrgyz Tian Shan, can provide key insights to these questions due to its well-documented late-Cenozoic tectonic activity and substantial Quaternary glacier cover. To address these questions, we investigated two valleys within the Terskey Range, separated by 40 km: the glacial Barskoon Valley and the mostly fluvial Kyzyl Suu Valley. We present new apatite (U-Th-Sm)/He (AHe) thermochronology data from valley-bottom samples in the Barskoon Valley and re-analyzed published low-temperature thermochronology data for both valleys. Inverse 3-D thermal-kinematic modeling indicates a shared tectonic history for both valleys, including accelerated thrusting starting at 10−8 Ma. In contrast to the Kyzyl Suu Valley, the Barskoon Valley additionally records a 22% increase in relief over the past ∼2 m.y., suggesting rapid valley deepening following the initiation of glaciation in the Terskey Range. These results imply that the impact of Quaternary climate change on erosion rates is highly spatially variable.