地学前缘 ›› 2025, Vol. 32 ›› Issue (5): 150-164.DOI: 10.13745/j.esf.sf.2024.12.87

• 沉积时空再造 • 上一篇    下一篇

显生宙海洋中的生物碳泵:有机质聚集的又一个重要机制

梅冥相1,2(), 王画1,*(), 覃英伦3, 黄文芳4   

  1. 1.中国地质大学(北京) 地球科学与资源学院, 北京 100083
    2.中国地质大学(北京) 生物地质与环境地质国家重点实验室, 北京 100083
    3.广西广投能源集团有限公司, 广西 南宁 530000
    4.广西地质调查院, 广西 南宁 530023
  • 收稿日期:2024-04-04 修回日期:2024-12-23 出版日期:2025-09-25 发布日期:2025-10-14
  • 通信作者: 王画
  • 作者简介:梅冥相(1965—),男,教授,主要从事沉积学和地层学研究工作。E-mail: meimingxiang@263.net
  • 基金资助:
    广西重点研发计划项目(2021AB30011);广西地矿局科研项目(GXDK202430)

The ocean’s biological carbon pump of the Phanerozoic: Another accumulation mechanism of organic matter

MEI Mingxiang1,2(), WANG Hua1,*(), QIN Yinglun3, HUANG Wenfang4   

  1. 1. School of Earth Sciences and Natural Resources, China University of Geosciences (Beijing), Beijing 100083, China
    2. State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences (Beijing), Beijing 100083, China
    3. Guangxi Investment Group Energy Group Co., Ltd, Nanning 530000, China
    4. Guangxi Geological Survey, Nanning 530023, China
  • Received:2024-04-04 Revised:2024-12-23 Online:2025-09-25 Published:2025-10-14
  • Contact: WANG Hua

摘要:

富有机质的细粒沉积物,即所谓的黑色页岩,常常形成重要的潜在性页岩气勘探目的层,其中有机质聚集作用被识别为3个基本模式:生产率、保存作用和沉积作用速率。需要指出的是,海洋的生物碳泵,是一个主要通过沉落颗粒(如浮游动物和细粒植物碎片等)向深海海底输出有机质,并最终鳌合在深部大洋沉积物之中的过程,也应该是显生宙深海沉积之中有机质聚集的又一个重要过程。在滇黔桂盆地中心地带的台间盆地相带之中,一套富有机质竹节石黑色页岩,累计厚度超过600 m,总有机碳(TOC)含量多为2%~4%,有的高达5%~6%,集中发育在广西南丹同贡剖面的埃姆斯期到弗拉斯期,代表一套品质较为优越的潜在性页岩气勘探目的层。更有意义的是,高密度保存在腐殖泥中的竹节石化石(含量超过30%)表明,浮游动物的生物碳泵,也应该是这些竹节石页岩富集有机质的另外一个重要机理。在广西罗城县小长安剖面下石炭统罗城组中,中-厚层含植物碎片的富有机质黑色页岩与中-厚层浅水灰岩一起构成潮下型米级旋回。尽管总体发育在浅缓坡台地背景之中,但是,黑色页岩层的TOC值普遍大于2%,代表一个细粒植物碎片生物碳泵的典型实例,从而间接地表明,在深水台间盆地相中,那些单层累计厚度超百米的富有机质页岩中的有机质的聚集(南丹同贡剖面的下石炭统鹿寨组),也受到相似机制的促进。这些发现和研究表明,除了经典的缺氧或生产率模型之外,确实存在着其他机制造成有机碳的聚集。

关键词: 海洋中的生物碳泵, 有机质聚集作用, 富有机质页岩, 显生宙

Abstract:

Organic-rich fine sediments, i.e., so-called black shales, are the main target rocks for unconventional oil and gas exploration and development. Three fundamental models have been identified for the accumulation of organic matter within organic-rich fine sediments: (1) enhanced organic productivity, (2) enhanced organic matter preservation, associated with reducing conditions, and (3) low sedimentation rate. Importantly and interestingly, the ocean’s biological carbon pump of the Phanerozoic—a sophisticated process by which organic matter is exported through sinking particles (e.g., zooplankton and phytodetritus) and finally sequestered in the deep ocean—should be considered another important mechanism for organic matter accumulation in organic-rich fine sediments, in addition to the above three fundamental models. A set of organic-matter-rich tentaculitid shales, with a thickness exceeding 600 meters and relatively high total organic carbon (TOC) values (commonly >2%, up to 5%-6%), was concentrated and developed from the Emsian to Frasnian Age (Devonian) at the Tonggong section in Nandan County, Guangxi, within the central Dianqiangui Basin. These shales represent an excellent potential target for shale-gas exploration. Furthermore, the high-density preservation of tentaculitid fossils within the sapropel demonstrates that organic matter accumulation in these tentaculitid shales is genetically linked to the zooplankton biological carbon pump. Within the Luocheng Formation (Lower Carboniferous) at the Xiaochangan section in Luocheng County, Guangxi, mid- to thick-bedded organic-rich black shales constitute subtidal carbonate cycles together with mid- to thick-bedded limestones of the shallow ramp facies. The relatively high TOC (>2%) and the presence of plant fossil fragments within these organic-rich black shales might represent an example of organic matter accumulation genetically linked to the phytodetritus biological carbon pump. Thus, the accumulation of organic matter within organic-rich black shales of the inter-platform basin facies (represented by the Luzhai Formation of the Lower Carboniferous at the Tonggong section, characterized by single horizons exceeding 100 meters in thickness) was also promoted by a similar mechanism. Therefore, this work reflects that there are other mechanisms for organic carbon accumulation in addition to the classical anoxia vs. productivity models.

Key words: ocean’s biological carbon pump, accumulation of organic matter, organic-rich shale, Phanerozoic

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