Assessing geologic inheritance and strain partitionning in an intraplate block corner junction area. Insights from high-resolution topographic data and multiple Quaternary dating methods in the Arpa Basin.

In the central Tien Shan, the largest intracontinental strike-slip fault is the northwest-trending Karatau-Talas-Fergana Fault (TFF), the southern extent of which remains debated. It is proposed that the TFF terminates in the Atushi Basin or continues southwards into the Tarim Basin.

We investigated the Arpa Basin, where the southernmost TFF segment intersects the South Tien Shan suture (STSs). High-resolution topographic data (derived from photogrammetry using SPOT 6/7 and drone images) reveal clear evidence of recent faulting along two parallel, reverse segments running at the toe of the mountain range and within the basin. Detailed mapping also revealed offsets in moraines and uplifted, abandoned alluvial surfaces. The combination of multiple dating methods (¹⁰Be, ²⁶Al, ³⁶Cl, OSL and ¹⁴C) at four sites across the Arpa Basin allows us to constrain late Quaternary slip rates for the last 100 ka.

In addition, the contradiction between the southwards TFF’s geological trace, which is easily observed on satellite images, and the absence of Quaternary surface ruptures associated with recent faulting leads us to propose that the two fault segments in the Arpa Basin reactivated the STSs and presently mark the southern termination of the active TFF in a horsetail thrust fault system.