摘要
越来越多的勘探资料显示中国西部主要的江河均不同程度地发育深厚覆盖层。覆盖层剖面从下往上可以分为三层。下部为冲积和冰水漂卵砾石层；中部为多成因的块（漂）卵（碎）石层，往往夹有粉细砂层或砂层透镜体；上部为冲积卵砾石层。年龄测定资料显示，谷底堆积物年龄一般在20-25ka，中部堆积物的年龄在16-19ka，均老于沿河分布的二级阶地。这说明，在距今25ka前，现今存在的河床基覆界面就巳形成，谷底25ka前切割如此之深应是河流强烈侵蚀的结果，这一侵蚀期正好与末次冰期内部的问冰段对应。
In the recent years, more and more exploration data show that deep overburdens are well developed in the west of China. According to the composition, three layers can be divided upward： alluvial and glacial fluvial boulders and pebbles gravel layer in the lower part; multi-genetic block （boulder） pebble （granule） layer in the middle part, generally intercalated with silt fine sand bed and sand lens; alluvial pebbles gravel layer in the upper part. Dating shows that the age of the lower part is about 20-25 ka, and that of the middle part is 16-19 ka. They are older than that of the second terrace along the river. These imply that the rock surface of the valley bottom was formed 25 ka ago by an intensive erosion event. This event is related with the second interglacial era of Würm.
出处
《成都理工大学学报（自然科学版）》
CAS
CSCD
北大核心
2006年第1期73-76,共4页
Journal of Chengdu University of Technology: Science & Technology Edition
基金
国家自然科学基金资助项目(40472143/D021490102002/D0214)
关键词
末次冰期
强烈侵蚀
深厚覆盖层
中国西部
last glaciation
intensive erosion
deep overburden of river bed
west of China
