VARIATION OF PRECIPITATION IN NAM CO,TIBET,SINCE THE LATE PLEISTOCENE AND ITSENVIRONMENTAL RESPONSE

Field surveys of the Nam Co-a large lake with the biggest area (1940 km²) and highest elevation above sea level (4718 m) in Tibet show that there are extensive lacustrine sediment around the Nam Co.Uranium-series and ¹⁴C dating indicate that the lacustrine sediments along the shores of the Nam Co are late Pleistocene and Holocene in age.The lake evolution was studied according to the change in distribution of lacustrine sediments of different ages around the Nam Co and the paleo-precipitation in the Nam Co drainage area was calculated.The study indicates that the climate in the study area turned from wet to dry since the late Pleistocene and that the precipitation has had a tendency of decrease since the Holocene.