冲积-河流相层序地层学研究

STUDY ON ALLUVIAL-FLUVIAL FACIES SEQUENCE STRATIGRAPHY

运用沉积学及层序地层学原理 ,分析了河流类型及其形成发育特征 ,借鉴国内外有关冲积河流环境下的层序地层模式 ,特别是近海冲积环境下层序地层模式 ,并以济阳坳陷新近系为例 ,建立了更具普遍意义的冲积河流相层序地层模式 ,探讨了不同体系域的特征及其与河流类型之间的关系。研究结果表明 ,冲积河流相地层的体系域划分具有 4分性特征 ,即主要发育有低水位体系域、扩张体系域、高水位体系域 ,当基准面缓慢下降时 ,还可发育收缩体系域。根据济阳坳陷新近系沉积特征 ,指出了各体系域对应的沉积体系及相类型。其中 ,低水位体系域时期以侵蚀下切、冲积扇辫状河沉积为主 ;扩张体系域时期是由辫状河向曲流河过渡 ;高水位体系域时期以曲流河为主 ;收缩体系域时期是由曲流河向辫状河过渡。

The principles of sedimentology and sequence stratigraphy were used to research the mode of sequence stratum of coastal alluvial environment. An universal mode for sequence stratum of alluvial-fluvial facies was established. The relationship between system tract and sedimentary facices was discussed on the analysis of river types of the Neogene in Jiyang Depression. The results show that there are four types of system tracts in alluvial-fluvial facies including low system tract, extension system tract, high system tract, contracting system tract. According to the sedimentary characteristics of the Neogene in Jiyang Depression, the types of sediment system and facies corresponding to the different system tracts were given. There were alluvial-braided river facies in low system tract. The braided river was transited to meandering river in extension system tract. There was meandering river in the high system tract, and the meandering river was transited to braided river in the contracting system tract.