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北羌塘下白垩统白龙冰河组黑色页岩地球化学特征与沉积古环境分析

Geochemical Characteristics and Sedimentary Paleoenvironmental Analysis of the Black Shale in the Upper Cretaceous Bailongbinghe Formation, North Qiangtang Depression

Environment and Resource / 2026,8(1): 105-113 / 2026-03-05 59 56

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• Authors: 王菲 付修根
• Information:

  西南石油大学地球科学与技术学院，成都

• Keywords:
  Black shale; Paleoenvironmental reconstruction; Organic matter enrichment; Semi-restricted bay
  黑色页岩; 古环境重建; 有机质富集; 半封闭海湾
• Abstract: The Early Cretaceous (Late Barremian–Early Aptian) organic-rich shales in the Qiangtang Basin constitute a significant hydrocarbon source rock series, whose formation is closely linked to specific paleoenvironmental conditions and organic matter (OM) enrichment mechanisms. Studies show that this shale sequence was deposited in a semienclosed relict bay–lagoon transitional environment. Based on lithological assemblages and geochemical characteristics, it can be divided into three distinct sedimentary units: micritic limestone at the base, black shale in the middle, and marl at the top. The black shale unit exhibits the highest total organic carbon (TOC) content. Paleoenvironmental reconstruction indicates that OM enrichment was controlled by multiple synergistic factors, including redox conditions, paleoproductivity, and paleoclimate. Redox proxies reveal that the micritic limestone was deposited under dysoxic– anoxic conditions, the black shale formed in a more strongly reducing anoxic–euxinic stratified water column, and the marl corresponds to oxic–suboxic conditions. This vertical variation directly influenced the preservation efficiency of OM. Paleoproductivity and paleoclimate indicators collectively indicate that the basal and middle units were deposited during periods of high marine primary productivity alongside a warm and humid temperate climate. In contrast, deposition of the upper unit occurred under a hot, arid climate with significantly reduced productivity. Particularly important is the presence of intermittent intense hydrothermal activity during the deposition of the black shale. This activity not only supplied abundant nutrients to the marine environment, stimulating productivity blooms, but the released reducing gases also helped maintain sulfidic conditions in the water column. Consequently, the development of Early Cretaceous organic-rich shales in the Qiangtang Basin resulted from a warm climate that enhanced the hydrological cycle and terrestrial nutrient input, thereby boosting productivity. Coupled with the topography of the semi-restricted bay, which facilitated water column stratification, these conditions collectively created an optimal environment for OM preservation. This study provides important geological insights for understanding the formation mechanisms of transitional facies source rocks and for hydrocarbon resource assessment in the Qiangtang Basin. 羌塘盆地早白垩世（晚巴雷姆期-早阿普提期）发育的富有机质页岩是该区域重要的烃源岩层系，其形成与特定的古环境背景和有机质富集机制密切相关。研究显示，这套页岩沉积于半封闭的残留海湾-潟湖过渡环境，根据岩石组合与地球化学特征可划分为三个清晰的沉积单元：下部的泥晶灰岩、中部的黑色页岩和上部的泥灰岩。其中，黑色页岩单元的总有机碳含量最高。古环境重建表明，有机质的富集受到氧化还原条件、古生产力、古气候等多因素协同控制。氧化还原指标显示，泥晶灰岩沉积于贫氧-缺氧环境，黑色页岩形成于更为强还原的缺氧-硫化分层水体，而泥灰岩则对应于氧化-次氧化环境，这种递变直接影响了有机质的保存效率。古生产力指标与古气候指标共同揭示，下部和中部单元沉积时期具有较高的海洋初级生产力，并伴随温暖湿润的温带气候；而至上部单元沉积时，气候转为炎热干旱，生产力显著降低。特别重要的是，在黑色页岩沉积阶段存在间歇性的强烈热液活动，其不仅为海洋提供了丰富的营养盐，刺激了生产力勃发，所释放的还原性气体也有助于维持水体的硫化条件。因此，羌塘盆地早白垩世富有机质页岩的发育是温暖气候强化了水文循环和陆源营养输入，提升了生产力；而半封闭海湾的地形易于形成分层水体，共同营造了优越的有机质保持条件。该项研究为深入理解过渡相烃源岩形成机制及羌塘盆地油气资源评价提供了重要的地质依据。
• DOI: https://doi.org/10.35534/er.0801013 (registering DOI)
• Cite: 王菲，付修根．北羌塘下白垩统白龙冰河组黑色页岩地球化学特征与沉积古环境分析［J］．环境与资源，8（1）：105-113.