根据对长江三峡阶地堆积物进行的野外调查与室内分析发现三峡阶地的成因具有以下特点:构成阶地上部的河漫滩相堆积、中部的冲积砾石层与作为阶地基座的基岩平台是在不同时期形成的;阶地上部河漫滩相堆积是在中全新世气候温暖、长江三峡高水位条件下形成的。因此,长江三峡阶地是在构造上升的基础上由于气候及长江三峡流量及水位变化而形成的,并非一定是间歇性构造上升的标志。

In the past, many investigators considered that the alluvial terraces in mountain areas are generally produced by the intermittent crustal uplift movement; or, it might result from a change to a more arid climate; or, from the greatly increased load derived from melting glaciers in the upstream region so that a valley floor is filled with alluvium by an aggrading stream.However, based on the field survey and the analyses of the chemical composition, mineral assemblage, pollen analysis and deposits on the alluvial iterraces distributed along the Three-Gorges course of the Changjiang River, the genetic mechanism is somewhat different from the above-mentioned sayings.(1)The three parts which constitute a terrace:the upper floodplain deposit, the middle alluvial gravel and the lower rock bench as base of terrace, were formed i n different periods.The rock bench of terrace as former river bed had been formed much earlier than the flood plain deposit.The middle gravel had been eroded before it Was covered by the floodplain deposit.(2)The upper floodplain deposit on terraces was formed under the condition of in-terglacial climate and high water level in Late Holocene.