Age Of Xiaoshagou Along The Yellow River Terrace In Lanzhou Basin

Terraces of the Yellow River in Lanzhou region are the most typical terrace sequences of China which are known as "Lanzhou Style Terraces". After many years of study, the Lanzhou Yellow River terrace sequence is constantly complemented and completed, the result of its dating is basically recognized and becomes the standard of regional comparison and the most detailed record of stepwise uplift of Qinghai-Tibetan Plateau since 1.6 Ma is also got from here. So the Lanzhou Yellow River terrace is thought to be the one of the most important evidences for the uplift of Qinghai-Tibetan Plateau and global climatic changes.The recent research of Lanzhou River terraces shows that 9 terraces are discovered in Lanzhou region. Xiaoshagou terrace is one of the two newly discovered terraces between the WuYishan terrace and the DunWashan terrace which were discovered originally. The dating of Xiaoshagou terrace is based on the Aeolian loess sequence-stratigraphic division and the relations of terraces, but it hasn't been measuring its absolute age. According to the study of magnetism stratum of the terrace alluvial flat and combining with paleosol sequence orbit to tune the age, we confirm that the age of the fifth Yellow River terrace in Lanzhou is 0.96Ma B.P., which really leads Lanzhou Yellow River terrace to get a complete age sequence and complements the Lanzhou Yellow River terrace research.The Kunlun-Yellow River Tectonic Movement is an intense tectonic movement which happened at a turn in the course of Early Pleistocene to Middle Pleistocene and has a scientific significance in the study of Qinghai-Tibetan Plateau. According to the result that it doesn't exist 0.6 Ma B.P.Yellow River terrace in Lanzhou Basin and by analyzing the result of high-resolution magnetism stratum in Kunlun Pass Basin, we know that the three stages of Kunlun-Yellow River Tectonic Movement aren't appeared in Lanzhou Basin. Based on the evidences of geology and geomorphology from 1.2 Ma B.P. to 0.78 Ma B.P., it can be inferred that Qinghai-Tibet Plateau and its surrounding areas like Qilian mountain, Sichuan-Yunnan region, Tianshan mountain and front of the Kunlun Mountain are directly affected by Kunlun-Yellow River Tectonic Movement.