天文旋回约束下的湖相泥页岩沉积作用：以济阳坳陷始新统为例

Our knowledge on mudrock is definitely poor in comparison to any other sedimentary rocks, though it makes up ca. 2/3 in sedimentary record. Cases have demonstrated that astrocycle controlled lacustrine deposition through studying littoral carbonates, but its influences on lacustrine organic-rich mudrock still need identification. Here we identify it using data from the lacustrine Eocene mudrocks of Jiyang Depression. The influence of each astrocyclic parameter (e.g., sunspot, precession, obliquity, eccentricity; cycle period from 10s’ to millions’ years) on mudrock deposition is studied by the correlation between astrocyclic parameters and the evolution of mineralogical composition. The mechanisms and effects of each astrocyclic parameter on mudrock deposition are thus defined, establishing the integrated distribution law from millimeter’ to dozens of meters’ scale. Combined with the above distribution law and a high-resolution cyclostratigraphy frame, the potential shale oil/gas reservoir is determined. This proposal tries to study mudrock deposition in a new perspective (astrocycle), providing a way for the development of “fine-grained sedimentology”.

泥页岩约占沉积岩的三分之二，然而对其成因的认识却比其它任何类型沉积岩都薄弱。已有研究表明天文旋回能够控制湖泊的沉积作用，但是对其过程机理的研究不够系统化，同时研究对象集中于湖盆碳酸盐岩，缺乏对大套富有机质深湖泥页岩的研究工作。本申请项目拟以济阳坳陷始新统湖相泥页岩为对象，根据天文旋回参数的周期性变化与泥页岩的物质组分、沉积机制演化的相关性，分析各参数（太阳黑子、岁差、斜率、偏心率等，周期从十余年到百万年级别）对泥页岩沉积的作用机制和影响过程，揭示天文旋回多参数综合作用下泥页岩从小尺度（厚度毫米、厘米级）一直到大尺度（可厚达数十米）的沉积演化规律。在此基础上，通过高精度等时旋回地层对比，明确有利页岩油气储层的分布特征和规律。本项研究将从一个全新的视角（天文旋回）揭示泥页岩的沉积作用，为细粒沉积学的发展提供了一个方向。

本项目以济阳坳陷中始新统湖相泥页岩为对象，根据天文旋回控制气候变化，进而控制沉积作用的原理，系统分析了天文旋回周期性变化与泥页岩的物质组分、沉积机制演化的相关性，建立各级别天文旋回参数（岁差、斜率、偏心率等）对泥页岩沉积的综合作用机制和影响过程，最终揭示天文旋回多参数综合作用下泥页岩从米级小尺度到百米级大尺度的沉积演化规律。在此基础上，通过高精度天文旋回格架等时旋回地层对比，分析了有利页岩油气储层的分布特征和规律。本项研究从天文旋回全新视角揭示泥页岩的沉积作用，为细粒沉积学的发展提供了一个方向，并助力页岩油气储层预测。