style="MARGIN: 0cm 0cm 0pt" class=MsoNormal>///The Quaternary debris-flow accumulations can provide rich information for geomorphic evolution,style="mso-spacerun: yes"> tectonic movement and climate change. The Waka debris flows is one of the major debris flows in the river segment and has successive series in the exposed sections. Detailed granularity,style="mso-spacerun: yes"> pollen,style="mso-spacerun: yes"> geochemical and textural studies reveal the formation processes of Waka debris flows. The age estimates of optically stimulated luminescence (OSL) using SAR protocol show that the occurrence of major debris flows started at around 12.6 ka B. P. style="mso-spacerun: yes"> and weakened until 4.5 ka B. P. style="mso-spacerun: yes"> in the upper space prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" /><st1:place w:st="on"><st1:PlaceName w:st="on">Jinshast1:PlaceName> <st1:PlaceType w:st="on">Riverst1:PlaceType>st1:place> valley. The age estimates of optically stimulated luminescence show that the occurrence of major debris flows corresponded to the obvious strengthened phase of the summer monsoons in the region. The formation characteristics and ages of the debris-flow deposits in the upper Jinsha River indicates that the occurrence of a mass of debris flows were a response to the intensified southwest monsoon in the southeast margin of the Tibetan Plateau since Early Holocene.