Lithofacies classification and origin of the Eocene lacustrine fine-grained sedimentary rocks in the Jiyang Depression, Bohai Bay Basin, Eastern China

•Lacustrine shale has strong heterogeneity in terms of its mineral composition.•Seven types of lithofacies developed in the Jiyang Depression.•Three types of lithofacies assemblages are present in the study area.•The Type C lithofacies assemblage is the most favorable exploration target.