济阳坳陷新近系层序地层及沉积体系

对济阳坳陷新近系层序类型、体系域类型等研究表明，冲积—河流相地层的体系域划分具有四分性特征。印主要发育低位体系域、扩张体系域和高位体系域，当基准面缓慢下降时，还可发育收缩体系域。冲积—河流环境下．准层序组边界主要依据较大规模河流底冲刷及厚层粗碎屑沉积、相对稳定的泥岩及古土壤、岩性组合及其测井响应等识别；有时，准层序组的边界与层序边界相一致，据此可将新近系分为10个准层序组。济阳坳陷新近系的沉积相类型及其演化研究表明，济阳坳陷新近纪由早至晚经历了冲积扇—辫状河沉积体系、辫状河—低弯度曲流河过渡体系和高弯度曲流河—泛滥平原沉积体系3个阶段，主要相类型有冲积扇相、辫状河及曲流河。

Sequence stratigraphy and sedimentary system of Neogene strata in Jiyang Depression

Types of sequence and system tracts of the Neogene strata in Jiyang Depression are studied. There are 4 types of system tracts in alluvial-fluvial facies: lowstand system tract, extension system tract, highstand system tract and even contraction system tract formed when base level declined slowly. Under the alluvial -fluvial environment,the boundary of subsequence sets can be distinguished with big scale bottom eroding of river and thick coarse clastic deposit, relatively stable mudstone and pal-eosol, lithological combination and its log responses, etc. The boundary of subsequence sets may be the boundary of the sequence. In view of the above, Neogene strata may be subdivided into 10 subsequence sets. Then the sedimentary facies types and their evolution are researched in Jiyang Depression. From early stage to late stage of the Neogene,the evolution of sediment environments went through three phases-alluviation fan-braided river system, braideded river-low-curvature meandering river system, and high-curvature meandering river-flood plain system. The main types of facies include alluvial fan, braided river and meander river.