通过天山北缘白杨河及玛纳斯河现代辫状河沉积作用为主的洪积扇的研究，认为此类洪积扇以活动的辫流带和洪水 期才发生沉积的漫洪带为特征。扇面上不能全区同时发生沉积，而是选择扇面低势能区发生沉积。辫状河道呈条带状分 布，与常规砾质辫状河沉积特征类似，并向扇缘散开，沉积的砾石条带物性好。洪积扇的发育受构造、气候、水系的共同 控制，这些条件决定了洪积扇的沉积特征及发育规模。准噶尔盆地西北缘三叠系古代洪积扇以辫状河道沉积作用为主，是 发育在盆地边缘低坡度洪积扇，更倾向于辫状河沉积特征。

This study was based on field study on Baiyanghe and Manas alluvial fans in North Tianshan Mountain. Braided belt is the main sedimentary area on the surface of arid braided alluvial fan. Sediments were unloaded in low potential area and sedimentary area laterally migrated along with the low potential area migrated. Braided channels show as string on the surface of alluvial fan and distributed in a wider area in the margin of fan. Gravel sediments in the braided belt have good porosity and permeability. Sedimentary characteristics and scale of alluvial fans are controlled by tectonic activities, climatic conditions, provenance supplies and river system. Braided alluvial fans are main ancient alluvial fans types in the northwest Junggar Basin and they occurred in the basin margin, showing more sedimentary characteristics of braided river.