湖相细粒岩二级指标划分法岩相分类及其应用实例

采用细粒沉积岩宏观观察刻画与显微刻画的方法,探索基于湖相细粒沉积纹层类型及其结构特征作为关键指标的细粒岩岩相成因。提出了湖相细粒岩岩相的划分指标和原则,即以细粒沉积纹层作为细粒岩岩相划分的重要指标。用两级核心指标作为划分湖相细粒岩岩相及亚类的依据,分为一级指标和二级指标。一级指标为岩石组成类型,分为泥质岩类、灰岩类以及泥质—灰质细粒岩等9个指标类型。二级指标为细粒纹层类型,主要有有机质纹层、云质纹层、方解石纹层、粉砂质纹层、膏质纹层、炭质纹层等类型,将细粒岩划分为21种岩相和33个岩相亚类,并分析了各岩相及亚相发育的沉积环境特征。

Petrographic Classification of Lacustrine Fine-grained Rocks Using a Two-level Index Division Method and A Case Study of Its Application

In this study,the macro/microscopic characterization of fine-grained rocks was observed,and the types and structural features of lacustrine fine-grained sedimentary laminae were taken as the key indicators by which to explore the genesis of fine-grained lithofacies.In addition,the classification indicators and principle of lacustrine fine-grained lithofacies were proposed.Fine-grained sedimentary laminae are important indicators for the classification of fine-grained lithofacies.Two levels of core indicators are proposed as the basis to classify the lacustrine fine-grained lithofacies and subtypes.The level one indicator is the rock composition type,which includes nine index types,e.g.argillaceous rocks,limestone and fine-grained calcareous rocks.The level two indicator is the fine-grained laminae type,mainly including organic,dolomitic,calcareous,silty,gypsum,and carbonaceous laminae.Based on these two levels,the fine-grained lithofacies are classified into 21 types and 33 subtypes.Subsequently,the characteristics of the sedimentary environment of each lithofacies are analyzed.