分支河流体系分类初探

Based on the research progress of distributive fluvial system（DFS），the geomorphic characteristics and main types of DFS were summarized，and the controlling factors of the formation and development of DFS were discussed. The results show that：（1）DFS is not a new or special river channel type，but a regular collection of multiple river channels. The geomorphic characteristics are shown as follows：the river network is radially distributed from one-point，various types of rivers develop together，the geometric shape of the river channel changes greatly，the sedimentary environment includes river channel and interchannel，and the sedimentary system is complex. The main types include alluvial fan，fluvial fan and megafan.（2）Based on DFS radius，area and their surface slope，DFS can be divided into three types as microDFS，macroDFS and megaDFS. The micro DFS，i.e.，alluvial fan，with a radius of less than 30 km，an area of less than 100 km² and a slope of greater than 1.0°. The macroDFS is called fluvial fan，with radius greater than 30 km but less than 100 km，their area is greater than 100 km² but less than 1000 km²，and slope is less than 1.0°. The megaDFS is megafan，which has a radius of greater than 100 km，an area of greater than 1 000 km² and a slope of less than 0.5°. The distribution ranges of the three types have certain overlap and repetition. It is also necessary to distinguish them by combining the hydrodynamic process and sedimentary characteristics of DFS.（3）Tectonic and climate are the most fundamental factors controlling the formation and distribution of DFS. Basin area and provenance may influence the total sediment supply and sediments composition of the depositional system. As an indirect factor，DFS slope may control the channel morphology and the bifurcation and crevasse of the channel together with channel flow and velocity，thus control the sedimentary environment and depositional facies distribution of the DFS.