Active tectonics in the upper reaches of the Yellow River from Lagan Gorge to Liujia Gorge, northwestern China: Insights from geomorphic indices

Abstract

The drainage basin of the upper reaches of the Yellow River from Lagan Gorge to Liujia Gorge, which spans Gonghe, Guide, Jianzha, Xunhua and Linxia basins, is located in the transition zone between the Qinghai–Tibet Plateau and the Loess Plateau, northwestern China. Its evolution is controlled by the northeastward growth and uplift of the Qinghai–Tibet Plateau. To characterize and quantify the response of surface processes to deep geological mechanisms and to investigate the types of Late Cenozoic tectonic deformation in the study area and the relationship with large geological hazards, we analysed various geomorphological indicators, combined with field observations and the estimated incision rates and established a reasonable tectonic deformation model. The results demonstrate that the variations in the geomorphic indices are highly consistent with active tectonics. Higher hypsometric integral (HI), higher normalized stream length‐gradient index (SLK), higher basin asymmetry factor (AF), higher drainage basin shape (BS) and lower ratios of valley floor width to valley height (VF) indicate higher tectonic uplift rate in the Jianzha‐Xunhua basins compared to other basins where there are many giant landslides. These giant landslides occurring there can probably be correlated with the vigorous tectonic activity, thus generating a great significance in geological hazard prevention and control along the upper Yellow River.