With the analysis of the element geochemistry characteristics,the ancient lake information evolution history of the argillaceous source rocks in Lucaogou(芦草沟)Formation in Sangonghe(三工河)area is reconstructed.According to the ancient lake information and total organic matter(TOC)characteristics of argillaceous source rocks,the study section is divided into 6 Subsections.Subsection I mainly developed low-quality source rocks.This is because of the arid climate,high salinity,low lake productivity,unstable preservation conditions in this Subsection.Subsection II mainly developed high-quality source rocks.This is because of the humid climate,low salinity,high lake productivity,stable preservation conditions in this Subsection.Though the paleoclimate was humid and preservation conditions were stable.Lake productivity and the water salinity changed frequently.So Subsection III mainly developed medium-quality source rocks.Because of the humid climate,high lake productivity,medium sedimentary rate and stable preservation conditions,high-quality source rocks were developed in Subsection IV.The preservation conditions were stable,but other ancient lake information changed frequently.Therefore,the quality of the formed source rocks in Subsection V was different.Subsection VI mainly developed high-quality source rocks because of the humid climate,medium sedimentary rate,high lake productivity,low salinity and good preservation conditions.In summary,the ancient lake information parameters and TOC characteristics of each Subsection are different from each other.
