Research progress and perspective on the characteristics and formation mechanism of laminae in lacustrine fine-grained sedimentary rocks

Key words: 
• fine-grained sedimentology /
• shale /
• laminae /
• heterogeneity /
• sedimentary characteristics /
• main controlling factors

Abstract: As an important carrier for paleoclimate reduction and unconventional oil and gas exploration, the study of fine-grained rock layers has attracted scholars' attention in recent years. However, the current academic research on the formation mechanism and corresponding identification characteristics of laminae in lacustrine fine-grained sedimentary rocks is still unclear. We systematically summarize the formation mechanism, sedimentary characteristics, and control factors of laminae in lacustrine fine-grained sedimentary rocks. Suspended sedimentation, remote dilution of gravity flow, bottom flow, volcanic hydrothermal fluid, and microbial action are all responsible for the formation of laminae in lacustrine fine-grained sedimentary rocks. In genetic identification, although different sedimentary processes may form similar laminae in composition, lamina thickness, particle size, and morphology, there are significant differences in laminae combinations, biological disturbances, and other sedimentary structural features. The formation and distribution of these laminae are controlled by two major factors: paleoclimate and paleogeography. Paleoclimate has a wide and complex control over laminae, and paleogeography controls the distribution pattern of laminae. From the perspective of theoretical development and practical application, there are still some problems in the study of laminae in lacustrine fine-grained sedimentary rocks. In the future, effective methods for extracting and naming laminae information should be developed based on the identification of the formation mechanism of the laminae, integrating the changes in the spatial scale, and focusing on cutting-edge issues such as paleoclimate reduction, carbon burial, life evolution, and Martian sedimentology to meet the major needs of unconventional oil and gas exploration.