What happened during the newer stage of mountain building that began about 25 million years ago?

The newer stage of mountain building in the Tien Shan, which began approximately 25 million years ago and continues today, is characterized by sudden movements of the Earth’s crust.1

This period of development has involved several significant geological processes:

• Sedimentation: Loose rock fragments have accumulated in valleys, with deposits in the Fergana Valley reaching thicknesses of nearly 5 miles (8 km). In many valleys, shallow lakes formed and subsequently evaporated, leaving behind salty deposits.1
• Glacial and Surface Activity: Glaciers produced moraines consisting of boulder-rich sediments, while gravel and loess accumulated in the valleys.1
• Faulting and Tectonics: Zones of faulting typically occur along the boundaries between ridges and valleys. Large-scale horizontal movements have taken place along the Talas-Fergana Fault, and deep faults in the region are associated with catastrophic earthquakes.1

Geologically, this current elevation is considered a consequence of the Indian subcontinent's penetration into Asia, which caused intracontinental crustal shortening in the Tien Shan, despite the range's great distance from India.2