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Abstract— <p>The Chang 7 Member of the Middle-Late Trassic Yanchang Formation in the Ordos Basin represents a significant Mesozoic lacustrine source rock and shale oil reservoir, as well as a valuable sedimentary archive for reconstructing continental paleoclimate evolution during the Mesozoic. Geochemical analyses of fine-grained lacustrine clastic rocks from drill cores in the basin center, considering the influences of provenance, diagenesis, sedimentary sorting, and sediment recycling, indicate climatic variations based on multiple weathering indices (e.g., CIA, CIW, PIA, WIP, and C-value). The results indicate that the provenance regions of the Chang 7 sediments underwent moderate to intense chemical weathering under a generally semi-arid to semi-humid and humid climate, and this long-term climatic regime was punctuated by four distinct phases. Lateral comparisons across the basin reveal spatial variability in weathering intensity inferred for the provenance regions and differences in inferred hydroclimatic conditions among regions, while maintaining an overall consistent evolutionary trend. Our findings suggest that the Chang 7 Member records interpretable geochemical signals of paleoclimate variability, providing useful constraints on Mesozoic continental climate evolution.</p>

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Continental Chemical Weathering and Paleoclimatic Implications of the Chang 7 Member, Yanchang Formation, Ordos Basin, Central China

  • 期刊论文

  • 发表日期：

    2026年4月30日

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  • Bo Chen,
  • Yuxuan Zhou,
  • Jianing Du,
  • Wenjie Niu,
  • Yijun Wang,
  • Tao Li,
  • Qihong Lei,
  • Yongchao Dang,
  • Leifei Wang,
  • Jinbo Zhang

摘要

Abstract—

The Chang 7 Member of the Middle-Late Trassic Yanchang Formation in the Ordos Basin represents a significant Mesozoic lacustrine source rock and shale oil reservoir, as well as a valuable sedimentary archive for reconstructing continental paleoclimate evolution during the Mesozoic. Geochemical analyses of fine-grained lacustrine clastic rocks from drill cores in the basin center, considering the influences of provenance, diagenesis, sedimentary sorting, and sediment recycling, indicate climatic variations based on multiple weathering indices (e.g., CIA, CIW, PIA, WIP, and C-value). The results indicate that the provenance regions of the Chang 7 sediments underwent moderate to intense chemical weathering under a generally semi-arid to semi-humid and humid climate, and this long-term climatic regime was punctuated by four distinct phases. Lateral comparisons across the basin reveal spatial variability in weathering intensity inferred for the provenance regions and differences in inferred hydroclimatic conditions among regions, while maintaining an overall consistent evolutionary trend. Our findings suggest that the Chang 7 Member records interpretable geochemical signals of paleoclimate variability, providing useful constraints on Mesozoic continental climate evolution.