Sedimentary Characteristics and Environmental Implications of the Terrces along Longtan River in Yichang

River terraces can record climate change information of river basins. The terraces of Longtan River in Yichang was selected as the research object and there are four typical river cross-sections, using the methods of sedimentology and environmental geochemical to study the sedimentary characteristics and environmental directives. The terrace sediments was tested by X-ray fluorescence spectrometry(XRF) in order to analysis the characteristics of material composition. Four indexes including CIA, ba, SiO₂/Al₂O₃and SiO₂/(Al₂O₃+Fe₂O₃) were selected to analyze the environmental evolution process in Longtan River, and the analysis results were explained by multivariate statistical method. In addition, using multivariable statistics to make further analyze. The results show that there are four level terraces distributing widely along Longtan River in Yichang. East bank developed erosion terraces, however, pedestal terraces are widely distributed in west bank. According to the correlation among chemical composition, it can be seen that the character and composition of the sediment are similar, which are rich in iron, aluminum, and stronger chemical corrosion. It conforms to warm wet chemical weathering environment in Longtan River. The test reasults and the multivariable statistics'conclusions can reflect that the degree of hot and humid environment in Longtan River tend to be weakened since the quaternary period. In addition, it enrichs the basic data of river terraces in Yichang, which reflects the natural geographical conditions and palaeoclimatic characteristics of sediments in Longtan River in a certain degree.