Development Of Fluvial Terraces In The Middle Reaches Of The Yuanjiang River And Its Response To Climate And-Neotectonic Movement

Fluvial terraces can reflect changes in paleoclimatic changes,neotectonics,and elevations of river erosion datums,thus deepening people's understanding of the process of regional geomorphology.The Yuanjiang River is an important water system flowing into the Dongting Lake in Hunan Province.It is an important tributary of the Dongting Lake water system in the middle reaches of the Yangtze River.It is an ideal area for studying the geomorphological evolution of the Yangtze River tributary and the response of the Neotectonic movement.The paper combines field investigation and indoor comprehensive analysis to identify the developmental characteristics of the fluvial terraces in the middle reaches of the Yuanjiang River.Combined with regional comparison,the development of fluvial terraces in the middle reaches of the Yuanjiang River and its response to climate and neotectonic movements are discussed,and the understanding of the evolution process of the Yuanjiang River basin is deepened.The paper has the following main conclusions:1.The development characteristics of the fluvial terraces in the middle reaches of the Yuanjiang River were ascertained.It was found that the terrace types of the study area were dominated by pedestal terraces and stacked terraces.The main stream of the mainstream was three to four river terraces,the tributary of the puddles is the highest in the five-level fluvial terraces..Combined with the dating data,it is determined that the chronological grid of fluvial terraces is from the mid-Pleistocene to the Holocene.2.The relationship between fluvial terrace development and climate change is analyzed.It is believed that the development of the main stream and tributary terraces in the middle reaches of the Yuanjiang River corresponds to the even phase of deep sea oxygen isotope.It indicates that the accumulation of fluvial terraces mainly occurs in the cold period,and climate change plays an important role in the formation of fluvial terraces in the middle reaches of the Yuanjiang River.3.The underground cutting rate of the river block in the study area was found to be 0.10-0.20m/ka,which revealed that the new tectonic movement in the study area is small,and the undercut rate of the main stream and the tributary river are basically the same,and there is a tendency to gradually strengthen.4.The regional comparative analysis shows that the formation age and the undercut rate of the study area are basically consistent with the Three Gorges section and the Lishui River Basin.The research results of the river topography in the middle reaches of the Yuanjiang River can provide a basis for the comprehensive study of regional geomorphology evolution.