永定河上游晚更新世晚期以来的堆积阶地年代测定

TERRACE DATING OF UPPER YONGDING RIVER DRAINAGE BASIN SINCE LATE PLEISTOCENE

应用1 4 C测年法和热释光方法对采自永定河上游晚更新世晚期以来形成的堆积阶地样品进行了年代测定。研究结果表明 ,永定河上游三条一级支流的低阶地形成时代具有一定的同时性 ,第三级阶地的下切时间大约在 30 0 0 0aB .P .;第二级阶地的下切时间大约在 10 0 0 0aB .P .;第一级阶地的下切时间大约在 4 0 0 0aB .P .。气候变暖对第二级阶地形成起主导作用 。

There are three levels of alluvial terrace in the upper Yongding River drainage basin since late Pleistocene. We obtained the timescale of terraces by radiocarbon dating method and luminescence dating method. It shows that the degradational episodes of these terraces occurred at the same period and the climate is the primary control factor and plays a greater role on formation of the terrace. The T 3, T 2 and T 1 began to degrade about 30ka B.P., 10 ka B.P., 4ka B.P., respectively.