Hui Xu's research while affiliated with China University of Geosciences (Beijing) and other places

Based on field investigation, optically stimulated luminescence (OSL) dating and sedimentary analyses, this research shows that the Yinduba paleolandslide-dammed lake (PDL) was formed by a catastrophic rock avalanche damming Jinsha River before 74 ka ago. According to the blocked ancient riverbed, the lake depth was determined about 110 m and the corresponding lake length was about 22 km when the lake level reached the peak. Geomorphologic features of lacustrine terraces at Yinduba and river terraces on the residual dam body and OSL dating results indicate that Yinduba PDL is a dammed lake with multi-stage outbursts. Following the peak, due to the multi-stage breaching of the dam body, the lake level experienced two major drops until the dam breached entirely after 36 ka. The large dam size, special sedimentary structure, and semi-arid climate contribute to the long life of Yinduba PDL, which existed for approximately 38,000 years from its formation to its extinction. This study supports the possibility of a large landslide-dammed lake having the life span of up to tens of millennia, and provides new evidence regarding the evolutionary history of a dammed lake.

The Walai rock avalanche (H/L ratio = 0.32), which was laterally and frontally confined occurred in the high mountainous areas of the eastern Tibetan Plateau. According to the field investigation and optically stimulated dating, the initial rock slope failure was determined to be a wedge failure controlled by bedding and two joint sets at approximately 38 ka ago. Based on the topography reconstruction, the deposited volume of this rock avalanche was estimated at 5.2 × 10⁷m³, which was 1.24 times the mass detached from the source area. We observed and mapped trimlines, longitudinal ridges, arched ridges, and lateral ridges associated with the rock avalanche. We also observed well-developed sedimentary features, including carapace facies, body facies, stratified structures, jigsaw fractures, directional arrangements, shear-damaged rock clasts, and interior folds. Measured grain size distributions indicated that the Walai rock avalanche fragmented within a relatively short travel distance after detachment from the source area, with no progressive reduction of grain sizes during the subsequent movement. Based on the morphological and sedimentary features, the emplacement process of the Walai rock avalanche was determined to be controlled by the local terrain and could be divided into four stages: an initiation stage (detachment), an accelerating stage (fragmentation), a longitudinal compression stage (momentum transfer), and a spreading stage (shearing).

Landslide events causing rivers to become dammed are common natural disasters in mountainous area. Based on the sedimentary facies analysis of 44 sections between proximal and distal parts of a dammed lake, this study reveals the sedimentary facies distribution of the Diexi Ancient Dammed Lake located in the upper Minjiang River, on the southeastern margin of the Tibet Plateau. Fluvial gravels and sand were deposited in the proximal part of the dammed lake. Rhythmically bedded silt and horizontally laminated silt to clay were deposited in the distal part of lake due to the deep and steady water conditions. After progradation of the fluvial system, flood sediments were deposited in the middle part of the lake. The flood carried a large amount of sediments into the lake, and the decelerating flow generated successively alternating layers of gravels and sand, followed by alternating layers of silt with low-angle cross-stratification, parallel bedding, and climbing ripples downstream. Gravel layers formed by four fluvial progradations were found based on the distribution of sedimentary facies in 44 sections. After the first fluvial progradation, lacustrine sediments at the highest point emerged from the water surface. The interval between the second and third fluvial progradation is relatively short, and only a terrace was formed, namely terrace VI. After the fourth fluvial progradation, terrace IV was formed. Although gravel layers formed by fluvial progradations corresponding to terraces II, III and V were not found, it can be determined that a terrace level does not necessarily correspond to a period of fluvial progradation. Therefore, the analysis of sedimentary facies upstream of landslide dams can be used as a supplementary method for inferring the evolution of the dammed lake.