SEQUENCES AND AGES OF RIVER TERRACES IN THE MIDDLE REACHES OF THE YELLOW RIVER

Based on the large amount of existing data,we worked out a uniform sequence with more accurate age for the terraces along the middle reaches of the Yellow River through comparison of the dating methods,the position of the dating samples and other factors.The drainage system of the middle reaches of the Yellow River can be divided into seven parts,i.e the Yellow River in Lanzhou,the Yellow River in Jin-Shaan gorge,the Yellow River in Yumenkou to Mengjin of Henan,the Weihe river,the Jinghe river,and the Luohe river.In order to establish the sequence and its chronological framework,we tried a variety of dating techniques in addition to the correlation of the terraces upstream and downstream.The age data of the Yellow River terraces in Lanzhou and along the lower reaches of Weihe River are relatively reliable,but those in the Jin-shaan gorge remain controversal.Further study is required as to the ages at the upstream terraces of the Wei River,Fen River,Jing River and Luo River.