A Late Pleistocene landslide damming event and its implications for the evolution of river valley landforms in the upper Jinsha River, southeastern Tibetan Plateau

Abstract

Numerous damming landslides have occurred at the southeastern margin of the Tibetan Plateau due to intense tectonic activities, strong river erosion, and extreme climate change. A Late Pleistocene paleo-landslide damming event has been detected in the Induba area in the upstream reaches of the Jinsha River, preserving various river-blocking phenomena, such as landslide dammed deposits and fluvial and paleo-dammed lacustrine sediments. Based on remote sensing and field investigations, we determined that the damming landslide originated from the inclined counter rock mass and experienced intense fragmentation, forming rock avalanches, which were possibly triggered by paleo-earthquakes or a combination of paleo-earthquakes and rainfall. To better understand the evolution of dam breaching and river valley landforms, optically stimulated luminescence (OSL) dating of lacustrine sediments was attempted. The results show that the landslide damming occurred ∼79.30 ka ago and formed a dammed lake upstream, which existed at least ∼20.86 ka before the dam breaching. The horizontal fluvial layers adhered to relict landslide deposits on the left bank, indicating that the process of dam breaching was conducted under the multiple circulations of lake water overtopping, fluvial deposition, and river undercutting. This study enriches our understanding of the formation of old dammed landslides and the evolution of river valley landforms in this region.