关键词: 河流沉积剖面, 古洪水, 渭河高陵段

Abstract:

Two high resolution profiles of fluvial sediments of Weihe River were found at Baijiaziu and Mafangtan in Gaoling county of Shaanxi province. After analyzing the grain size composition for 147 samples from Baijiaziu and Mafangtan profiles and the chronology material recorded by historical books, we studied the flood depth, flood level distribution and climatic change between 1 500— 1 100 a BP. The grain-size parameters（Mz, Md, σ, Sk, Kg）shows that the fluvial sediments of Weihe River between 1 500—1 100 a BP, which is 3.4 m in thickness, consists of at least nine fluctuations of grain-size, which clearly indicates 9 stages of large scale flood. The flood depth recorded by Baijiaziu and Mafangtan profiles was obviously more than 2 m, which was much deeper than that of the present. The first, the third, the fifth, the seventh and the ninth stages of flood scale was much smaller than the second, the fourth, the sixth and the eighth flood. The second, the fourth, the sixth and the eighth flood were caused by the distinct increasing of rainfall, when the average annual rainfall might be 800~900 mm. The first, the third, the fifth, the seventh and the ninth flood were basically due to the concentricity of rainfall or the certain increasing of rainfall.

Key words: fluvial sediment profile, paleoflood, Weihe river in Gaoling