A Late Pleistocene river-damming landslide, Minjiang River, China

Abstract

An ancient, large-scale, river-damming landslide in Koushan Village, Wenchuan County, Sichuan Province, located in the upstream of the Minjiang River, had a large influence on the valley evolution of the Minjiang River. Our investigation estimated that the landslide volume was 1.5 billion m 3 . The elevation of the scarp is 2700 m, 1000 m above the present accumulation of the landslide. The residual dam is comparatively complete, with calcium cementation. The highest point of the dam is 221 m higher than the Minjiang River. The dammed lake extends for 38 km and reaches as far as Maoxian County. The investigation results indicate that an earthquake was probably the main cause of the landslide. The damming mechanism was associated with rock avalanches. These rock avalanches subsequently blocked the Minjiang River. The dam exhibits multi-stage breaching, which can be divided into overflow erosion and rapid cutting stages. The 14 C dating results indicate that the landslide occurred at least 22,000 years ago and that the dam was breached at least 11,700 years ago.