## 6 Conclusions  
This study focuses on the Jurassic Ziliujing Formation Da'anzhai Member shale in the central part of the Sichuan Basin, systematically characterizing its geological features. Through the application of geochemical methods, we aimed to reconstruct the paleo-depositional environment of shale with different lithofacies and explore the mechanisms of organic matter enrichment. The key findings and conclusions derived from this investigation are outlined below.  
The Da'anzhai Member shale in the study area exhibits a distribution of total organic carbon content ranging from 0.4% to 2.3%, with a mean value of 1.1%. The predominant mineral component is clay minerals, followed by siliceous minerals, with carbonate minerals showing the lowest content. Through the analysis of mineral composition and organic matter content, three lithofacies types are distinguished in the Da'anzhai Member shale in the study area: organic-rich argillaceous shale, organic-rich mixed shale, and organic-poor argillaceous shale.  
Utilizing geochemical methods, the paleo-depositional environment of the Da'anzhai Member shale in the study area has been effectively reconstructed. The sedimentation period of the Da'anzhai Member was characterized by a warm and humid climate, coupled with moderate to strong weathering conditions in the watershed of the shale clastics source. The primary deposition occurred in an oxygenated environment with freshwater to brackish conditions. The distinctions in sedimentary environments among shale lithofacies are primarily manifested in paleoclimate, redox conditions, terrestrial debris influx, and salinity.  
Integrating proxies for paleo-depositional environments with a TOC content analysis, it becomes evident that redox conditions and paleoclimate are the predominant factors influencing organic matter enrichment in the Da'anzhai Member shale in the study area. Salinity, albeit to a lesser extent, also contributes to organic matter enrichment, whereas the input of terrestrial debris and paleo-productivity does not exhibit significant control over organic matter enrichment.  
Writing--original draft, formal analysis, investigation, and data curation, Y.P.; Writing--review and editing, software and visualization, Y.F.; Writing--review and editing, methodology and validation, S.C.; Conceptualization, methodology and funding acquisition, E.W. All authors have read and agreed to the published version of the manuscript.  
This research was supported by the open fund from the State Key Laboratory of Shale Oil and Gas Enrichment Mechanism and Effective Development of SINOPEC (33550000-22-ZC0613-0337).  
Not applicable.  
The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.  
Author [PERSON] was employed by the company China Petroleum & Chemical Corporation. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The funder had no role in the design of the study; in the collection, analysis, or interpretation of data, in the writing of the manuscript; or in the decision to publish the results.