ACS Earth and Space Chemistry· 2026Q2
Sedimentary Environment and Organic Matter Enrichment of Shale under Tectonic-Depositional Differentiation from the Lower Cambrian Niutitang Formation Guizhou, South China
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- 2026year
Short summary
Shale organic matter enrichment in South China's Niutitang Formation is strongly linked to tectonic deformation intensity, with the most deformed zone (QinX1) showing the highest total organic carbon (TOC) at 4.83% due to low productivity, low dilution, and strong preservation.
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Key points
- Tectonic deformation intensity directly correlates with shale organic matter enrichment, with higher deformation leading to higher TOC.
- The strongly deformed zone (QinX1) achieved its high TOC (4.83%) through low productivity, low dilution, and strong preservation.
- The moderately deformed zone (YF1) displayed low TOC (1.28%) despite high productivity, attributed to high dilution and weak preservation.
- Paleoenvironmental proxies indicate diverse depositional conditions, including varying water depths, redox states, and climates across the deformation zones.
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Abstract
Abstract To investigate variations in depositional environments and organic matter (OM) enrichment across different tectonic deformation zones, this study analyzed samples from three wells with contrasting deformation intensities: QinX1 (strongly deformed), YF1 (moderately deformed), and QiX1 (weakly deformed). Elemental geochemistry was used to characterize paleosedimentary environments and mechanisms of OM enrichment. Results show that paleoenvironmental assemblages under different tectonic deformation regimes significantly influence OM enrichment. Total organic carbon (TOC) is highest in well QinX1 (mean 4.83%), followed by QiX1 (3.26%) and YF1 (1.28%). Ga/Rb–K2O/Al2O3 cross-plots suggest warm-humid deposition for QiX1, arid-cold for QinX1, and transitional climate for YF1. Paleowater depth proxies (Fe/Co and Zr/Al) indicate a decreasing water depth gradient from YF1 through QinX1 to QiX1. Redox proxies (U/Th and Ni/Co) indicate predominantly anoxic conditions for QinX1 and YF1, and dysoxic to anoxic conditions for QiX1. Mo/TOC ratios reflect moderate restriction in QinX1 (mean 16.94), weak restriction in YF1 (68.48), and moderately strong restriction in QiX1 (8.41). Paleoproductivity proxy (Babio) shows the highest value in well YF1 (mean 5616.57 μg/g), whereas wells QinX1 (2019.39 μg/g) and QiX1 (2410.13 μg/g) exhibit relatively lower productivity. Terrigenous input proxy (Ti/Al) shows a decreasing trend from YF1 (mean 0.082) through QiX1 (0.061) to QinX1 (0.058). Hydrothermal activity proxy (Co/Zn) exhibits a decreasing trend from YF1 (mean 0.091) through QinX1 (0.107) to QiX1 (0.136). Comprehensive analysis reveals that the strongly deformed zone (Well QinX1) features low productivity, low dilution and strong preservation; the moderately deformed zone (Well YF1) shows low TOC value characteristics of high productivity, strong dilution and weak preservation; and the weakly deformed zone (Well QiX1) exhibits balanced enrichment with moderate productivity, moderate dilution and relatively strong preservation.
The authors' abstract, as published at the source. ACS Earth and Space Chemistry, 2026 · DOI ↗
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Field: Mechanics of Materials
Mechanics of MaterialsEngineering