Lake-Level Change Reconstruction Using Environmental Proxies: A Case Study of the Lower Part of the Liwaxia Formation in the Liupanshan Group

Key words: 
• lake level /
• sedimentary facies /
• environmental proxies /
• Liupanshan Basin

Abstract: [Objective]Studying lake-level changes is an important approach to understanding regional tectonic and climatic evolution, while how to accurately interpret or quantitatively reconstruct lake-level changes has always been a subject of ongoing exploration. [Methods]In this study, by utilizing environmental proxies and integrating traditional sedimentary environment analysis, observations and measurements of environmental indicators (chroma, magnetic susceptibility, CaCO3 content, and total organic carbon (TOC) content) were conducted on the approximately 10-meter-thick lacustrine sediments in the lower part of the Liwasxia Formation of the Liupanshan Group, where the tectonic setting of the Liupanshan Basin is relatively stable.This research investigated the lake-level changes recorded by these sediments and analyzed the applicability of environmental proxies. [Results]This research investigated the lake-level changes recorded by these sediments and analyzed the applicability of environmental proxies. The results indicate that from the lower to the upper part of the sedimentary sequence, the sedimentary subfacies develop in the order of shallow-water delta plain, shore-shallow lake, semi-deep lake, shore-shallow lake, semi-deep lake, and shore-shallow lake, forming two lake-level change processes characterized by a transition from shallow to deep water. Environmental proxies exhibit significant variations across different sedimentary subfacies: chroma parameters show the largest fluctuations in the shallow-water delta plain facies and gradually become stable upward; magnetic susceptibility demonstrates a gradual decrease from the bottom to the top of the sequence; CaCO3 and TOC contents fluctuate considerably but generally show an increasing trend. Specifically, in the microfacies dominated by argillaceous sediments within the shore-shallow lake facies, the a* value and TOC content can serve as indicators for determining the lake-level elevation, while the CaCO3 content can be used to identify the driving mechanisms of lake-level changes during this period. In contrast, in the microfacies dominated by marl-limestone sedimentary assemblages, the CaCO3 content and TOC value can indicate the lake-level elevation.[Conclusion]Based on the sedimentary facies and indicator results, it can be concluded that the aforementioned indicators are relatively sensitive to feedback on lake-level changes. However, a single indicator cannot be directly used as a basis for characterizing lake-level changes and their driving mechanisms; instead, a comprehensive discussion should be conducted in combination with sedimentary facies and lithological associations.