云南三江一河典型地区河谷第四系发育特征

三江一河（金沙江、怒江、澜沧江、红河是流经云南境内的４条主体水系，将上述４条河流河谷第四系的野外观察加以总结得出；金沙江河谷局部发育早一中更新世的湖相层和河湖相层，常形成晚期阶地的基座，晚更新世至全新世冲积层构成四级阶地；怒江河谷第四系发育较差，在六库的上游河谷中冲积层极不发育，只有局部地方有少量的河漫滩砂砾层（全新世），在六库至过街河段中，尤其是过街盆地，发育有中更新世至全新世的冲积层和洪积层，前者构成五级阶地，后者形成巨大的洪积扇分布在河流右岸的谷底或苍坡上；澜沧江除景洪、勐罕（橄榄坝）盆地外，其它河段主要为峡谷，第四系很少，在景洪盆地中发育有第二、第一级阶地和河漫滩冲积层；红河的第四系有中更新世至全新世的冲积层，并构成五级阶地。基于上述第四系特点，简要地讨论了这４条河流的形成时代。

ON VALLEY QUATERNARY IN THE JINSHA RIVER,NUJIANG RIVER, LANCANG RIVER AND YUANJIANG RIVER, YUNNAN PROVINCE

he four rivers in Yunnan Province, which are Jinsha River, Nujiang River, Lancang River and Yuanjiang River (also named Honghe River), form the main drainage and control the drainage network in the whole province. Their Quaternary deposits represent the characteristics of the valley Quaternary strata Df Yunnan. In the Jinsha River, locating at the upper reaches of the Yangtze River, the Early to Middle Pleistocene strata mainly consist of the lacustrine beds, and occur at the several places, for example, Jinjiangjie, Dukou etc.Late Pleistocene to Holocene alluviums widespreadly scatter along the valley. In the Nujiang River, Quaternary sediments poorly developed. In the upper reaches to Liuku city locating on the bank of the Nujiang River, the only alluvial deposits are few sandy gravel beds (river bed, Holocene). In the valley from Liuku to Daojie basin,especially in the Daojie basin, alluviums and proluviums completely developed, and may be divided into the Middle Pleistocene, Late Pleistonene and Holocene in age. It is worth pointing out that the proluvial deposits are almost distributed at the bottom and on the wall of the valley to the west of the Nujiang River. The valley of Lancang River, except for Jinghong basin and Ganlan basin, all is canyon, therefore Quaternary sediments are few. In the Jinghong basin and Ganlan basin, there are the second and first terrace and river bed alluviums that may be Late Pleistocene and Holocene in age. The Quaternary of Yuanjiang River in the genetic type and age are similar to those of the Nujiang River,and are made up of the Middle Pleistocene to Holocene alluviums that are divided into the five terraces. Finally, the four river developed historis are briefly discussed in the paper.