THE CHARACTERISTICS OF RIVER TERRACES AND ACTIVITY OF THE FAULTS IN THE OUTLET OF HEISHAN GORGE OF THE YELLOW RIVER, THE NORTHEAST TIBETAN PLATEAU

River terraces were developed and preserved well in the outlet of Heishan Gorge of the Yellow River, Northeast margin of the Tibetan Plateau. The terraces not only documented the uplift history of northeast part of the Tibetan Plateau since Quaternary, but its characteristics and distribution also reflect the active features of F 8(7)and F 201 faults. Detailed studies show that there are seven terraces preserved to the south of F 8(7) fault but only five terraces preserved to the north of F 8(7) fault and to the north of F 201 fault. All the terraces are pedestal terrace. The frontier lines of the TerraceⅠ,Ⅱ and Ⅲ is continuous, but the width of Terrace Ⅲ increase sharply across the F 8(7) and sinistral displacement of the frontier line of Terrace Ⅳ and,Ⅴ amounts to 150 meter. The width of TerraceⅡ changes from 200 meter to 710 meter across F 201, and the frontier line of the terrace Ⅲ, Ⅳ andⅤ displaced to 400 meter across F 201. Those changes of width and displacement of the terraces documented F 201 and F 8(7) fault activity since Pleistocene, which provide us with important data for evaluation of fault activity.