Nature and timing of large landslides within an active orogen, eastern Pamir, China

Large-scale landsliding (involving >> 10(6) m(3) in volume) is important in landscape development in high mountains. To assess the importance of large landslides in high mountains, four large landslides (Bulunkou, Muztagh, Taheman, and Yimake) were mapped in the NE Chinese Pamir at the westernmost end of the Himalayan-Tibetan orogen and dated using Be-10 terrestrial cosmogenic nuclides. The Bulunkou landslide at the southernmost end of Muji Valley is composed of similar to 1.7 x 10(7) m(3) of landslide debris and has an age of 2.0 +/- 0.1 ka. The Muztagh landslide, located on the SW side of the massif Muztagh Ata, is composed of similar to 4.7 x 10(8) m(3) of debris, and has an age of 14.3 +/- 0.8 ka. The Taheman landslide, located south of Muztagh Ata, is composed of similar to 2.6 x 10(8) m(3) of landslide debris and has an age of 6.8 +/- 0.2 ka. The Yimake landslide, on the northern frontal range of the Pamir at the southwestern end of the Tarim basin, is composed of similar to 1.4 x 10(9) m(3) of landslide debris and has an age of 7.1 +/- 0.6 ka. Two other large landslides are present in the region, the Aerpa Aigezi (on a tributary of the Gez River) and the Bile Jiyi (on the Yarkand River) landslides, and are composed of similar to 1.6 x 10(7) m(3) and similar to 5.2 x 10(6) m(3) of landslide debris, respectively. However, the Aerpa Aigezi and Bile Jiyi landslides were not studied in as much detail or dated because of their inaccessibility. Given the tectonically active nature of this region, with numerous active faults, and the morphology of the landslides, these landslides were likely triggered by earthquakes. However, other causes - including long-term increased precipitation and geologic bedrock structure - could be important contributing factors in their formation. (C) 2012 Elsevier B.V. All rights reserved.