利用环境代用指标恢复湖平面变化:以六盘山群李洼峡组下部为例
- 收稿日期:
2025-09-05
- 网络出版日期:
2026-04-22
摘要: 【目的】研究湖平面变化是认识区域构造及气候演变的重要途径,而如何准确理解或重建相对湖平面变化一直是不断探索的问题。【方法】本文利用环境代用指标,结合传统的沉积环境分析,通过对六盘山盆地构造相对稳定的六盘山群李洼峡组下部厚约10米的湖相沉积物进行观察与环境指标(色度、磁化率、CaCO3和总有机碳(TOC)含量)测量,探讨了该段沉积物记录的湖平面变化,并对环境代用指标的适用性进行了分析。【结果】结果显示从下向上发育浅水三角洲平原-滨浅湖-半深湖-滨浅湖-半深湖-滨浅湖沉积亚相,构成两个由浅变深的湖平面变化过程。环境代用指标在不同的沉积亚相中变化明显:色度参数在浅水三角洲平原相波动最大,向上逐渐平缓;磁化率呈现由底至顶逐渐降低;CaCO3与TOC波动较大,但总体为逐渐升高趋势。其中,滨浅湖相中以泥质沉积为主的微相,a*与TOC可作为判断湖平面高低的指标,CaCO3含量则可用于判断此时湖平面变化的驱动机制;而在以泥灰沉积组合为主的微相中,CaCO3含量与TOC值则可以指示湖平面的高低。【结论】依据沉积相与指标结果,可以认为上述指标对湖平面变化的反馈较为敏感,但单一指标不能直接作为刻画湖平面变化与驱动机制的依据,需结合沉积相与岩性组合进行综合讨论。
Lake-Level Change Reconstruction Using Environmental Proxies: A Case Study of the Lower Part of the Liwaxia Formation in the Liupanshan Group
- Received Date:
2025-09-05
- Available Online:
2026-04-22
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.