THE FORMATION OF RIVER TERRACES AND EVOLUTIONOF DRAINAGE SYSTEM IN THE MIDDLE YELLOW RIVER
黄河中游河流阶地的形成与水系演化

: In the past many scientists had, from distinct data, estimated the birthday of the Yellow River at the Pliocene, the Early Pleistocene, the Middle Pleistocene, or the Late Pleistocene. In this article the author is the first to propose a new position: the Yellow River and its main tributaries were formed in 1670-1450 ka B. P., i.e. early-middle Pleistocene, and after that 6 terraces and 2 valley flays have developed. The ages (ka B. P.) are as follows: TG, 1670--850, T5, 850-470, T4, 470-100, T3,100-10, T2, 10-0.7, T1, 0.7-0.3, high valley flay 0.3-0.15, lower valley flay 0.15-0. The periods of hydrographic evolution may be di- vided into 4 main stages and 9 substages since the Pliocene. These new conclusions are obtairied on the basis of a host of field investigations along the Yellow River and its tributaries, and according to the principle of "paleosol-dating method" suggested by the author.