###### Abstract  
Jurassic lacustrine shale in the Sichuan Basin is a focal exploration area in China, while the pronounced heterogeneity presents challenges, necessitating detailed research as a prerequisite. This study aims at the Jurassic Ziliujing Formation Da'anzhai shale in the central Sichuan Basin, systematically characterizing its geological features. Employing geochemical methods, we reconstructed the paleo-sedimentary environments and explored the mechanisms behind the organic matter enrichment. The findings reveal that the Da'anzhai shale exhibits three lithofacies: organic-rich argillaceous shale (ORA), organic-poor argillaceous shale (OPA), and organic-rich mixed shale (ORM). The sedimentary period was marked by a warm and humid climate, predominantly depositing in anoxic environments with freshwater to brackish conditions. The watershed areas that are provenance sources for the shale clastics are experiencing strong weathering. Significant differences in the sedimentary environments of various lithofacies' shale were observed. Redox conditions and paleoclimate were identified as the primary factors controlling organic matter enrichment in the Da'anzhai shale of the study area. Salinity also played a role in organic matter enrichment, while terrigenous debris influx and paleoproductivity did not exert a significant controlling effect on organic matter enrichment. Utilizing the reconstructed ancient sedimentary environments, we developed sedimentary models for different lithofacies' shale, contributing to a deeper understanding of lithofacies' diversity and the mechanisms governing organic matter enrichment in lacustrine environments. This study provides new information for further understanding the response mechanism of lacustrine shales to the Toarcian Oceanic Anoxic Event in the Early Jurassic from the perspective of elemental geochemistry. lacustrine shale; paleoenvironment; organic matter enrichment mechanisms; Sichuan Basin 2020  
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[PERSON], [PERSON], [PERSON], [PERSON], E. Sedimentary Environment Reconstruction and Organic Matter Enrichment Mechanisms in Various Lithofacies of the Lacustrine Shale: A Case Study of the Da'anzhai Member, Central Sichuan Basin, China  
To identify favorable exploration targets, previous researchers have proposed various methods. [PERSON] et al. (2019) innovatively suggested a matching source kitchen, reservoir depositional facies, and other key factors in oil and gas exploration ([PERSON] et al., 2022). [PERSON] et al. (2022) proposed that determining favorable exploration lithofacies is a primary task in lacustrine shale exploration ([PERSON] et al., 2022). [PERSON] et al. (2022) suggested that the selection of favorable exploration \"sweet spots\" should consider the combination of sedimentary lithofacies and organic lithofacies ([PERSON] et al., 2019). Among these methods, there is a strong emphasis on the significant role of lithofacies in determining sweet spots for shale oil. The differences in lithofacies reflect variations in sedimentary environments and geological characteristics of rocks ([PERSON] et al., 2022). Therefore, lithofacies division provides new insights for refined research. Revealing the sedimentary background of different lithofacies helps pinpoint favorable exploration targets, holding significant implications for improving exploration efficiency. The exploration of Jurassic strata in the Sichuan Basin currently serves as a pivotal focus in lacustrine shale oil exploration in China. Within the Jurassic strata, three sets of organic-rich shale have been identified: the Lianggaoshan Formation, and the Da'anzhai and Dongyuemiao Members of the Ziliujing Formation ([PERSON], 2016; [PERSON] et al., 2022; [PERSON] et al., 2022). Significant breakthroughs have been achieved in the Lianggaoshan Formation and Dongyuemiao Member ([PERSON], 2016; [PERSON] et al., 2022). However, substantial progress has yet to be made in the exploration of the Da'anzhai Member shale.