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从古代河流沉积体系中识别出了河型随时间演化的 6种模式 :辫状体系→曲流体系 ,曲流体系→辫状体系 ,辫状体系→网状体系 ,网状体系→辫状体系 ,网状体系→曲流体系 ,曲流体系→网状体系。依据具体实例讨论了 3类河型的 6种转化模式的特点及其成因 ,分析了对应于各演化模式的古河型可能的空间分布特征。系统总结了古代冲积河型演化的一些主要影响因素 :①河道比降 ;②河岸及河漫滩物质组成 ;③植被覆盖度 ;④流域来沙量大小及来沙组成 ;⑤流量变率 ;⑥气候因素 ;⑦构造因素 ;⑧海平面变化。认为这些因素对河型的控制往往彼此相关 ,但在不同时期、不同地点其影响作用的相对大小有所不同。与现代冲积河型空间转化的影响因素相比 ,地质构造作用和古气候变化是古代河型演化的主要控制因素。
Six patterns of evolution of river patterns with time have been identified from ancient river sedimentary systems: braided systems → meandering systems, meandering systems → braided systems, braided systems → reticular systems, reticular systems → braided systems , Mesh system → Meander system, Meander system → Mesh system. Based on the concrete examples, the characteristics and causes of six transformation modes of three types of river types are discussed. The possible spatial distribution characteristics of ancient river types corresponding to each evolution mode are analyzed. Some main influencing factors of the evolution of ancient alluvial rivers are summarized as follows: (1) the ratio of river channel; (2) the composition of river bank and floodplain; (3) the vegetation coverage; (4) the size and composition of sediment in the basin; (5) the flow rate variability; (6) ; ⑦ structural factors; ⑧ sea level changes. It is considered that the river-type control of these factors is often related to each other, but the relative sizes of their influence are different at different periods and locations. Compared with the influencing factors of spatial transformation of modern alluvial rivers, the geological structure and paleoclimate change are the main controlling factors for the evolution of ancient river systems.