Key words: 
• sedimentary environment /
• organic matter enrichment mechanism /
• Niutitang Formation /
• Well Guidudi 1 /
• Southern Guizhou Depression

Abstract: [Objective] The sedimentary paleoenvironmental characteristics of the Lower Cambrian Niutitang Formation in the Southern Guizhou Depression were studied, and the mechanism of organic matter enrichment was analyzed to support shale gas exploration and development in the area. [Methods] Based on the core and testing analysis data of Well Guidudi 1, the mineral composition, lithofacies characteristics, and geochemical characteristics of the Niutitang Formation were analyzed to study the sedimentary processes and characteristics of ancient marine environments, such as redox conditions, paleoproductivity, input of terrestrial debris, and degree of water retention. The sedimentary evolution process and organic matter enrichment mechanism of the Niutitang Formation were explored. [Results] The results indicate that the first section of the Niutitang Formation developed organic rich siliceous shale, organic rich silty siliceous shale, and organic mixed shale, mainly involves suspended sedimentation of mud and biological sedimentation of siliceous matter. The second section of the Niutitang Formation was mainly composed of poor organic clayey shale, with the main sedimentary model being mud coagulation and sedimentation. The third section of the Niutitang Formation developed organic and calcareous mixed shale, with the main sedimentary model being calcium chemical deposition and mud flocculation deposition. [Conclusions] The ancient marine environment and organic matter enrichment during the sedimentation period of the Niutitang Formation in the study area showed obvious stages. During the first sedimentary period of the Niutitang Formation, the ancient marine environment was controlled by the high productivity level and strong reducing conditions formed by rapid marine invasion, resulting in a significant enrichment of organic matter. During the second sedimentary period of the Niutitang Formation, the organic carbon content was low due to the combined effects of oxidative environment and dilution from high terrestrial debris supply. During the third sedimentary period of the Niutitang Formation, it is speculated that the strong retention environment promoted the deposition of carbonate minerals and the enrichment of organic matter due to the influence of underwater ancient uplift. The research results can provide a reference for the evaluation of shale gas resource potential in the Niutitang Formation of Southern Guizhou Depression.