四川盆地北部下二叠统栖霞组陆源碎屑岩的发现及其指示意义
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1.油气藏地质及开发工程全国重点实验室;2.自然资源部深时地理环境重建与应用重点实验室;3.自然资源部深时地理环境重建与应用重点实验室,成都理工大学沉积地质研究院;4.中国石油西南油气田公司勘探开发研究院

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国家自然科学基金项目(面上项目,重点项目,重大项目)


The discovery of terrigenous siliciclastic rocks and its significance of the Lower Permian Qixia Formation in northern Sichuan Basin
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1.State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Chengdu University of Technology,Chengdu;2.Key Laboratory of Deep-time Geography and Environment Reconstruction and Applications,MNR Institute of Sedimentary Geology,Chengdu University of Technology,Chengdu;3.Key Laboratory of Deep-time Geography and Environment Reconstruction and Applications, MNR & Institute of Sedimentary Geology, Chengdu University of Technology,;4.Key Laboratory of Deep-time Geography and Environment Reconstruction and Applications, MNR & Institute of Sedimentary Geology, Chengdu University of Technology;5.Exploration and Development Research Institute, PetroChina Southwest Oil & Gasfield Company;6.State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology

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    摘要:

    在四川盆地北部旺苍双汇剖面下二叠统栖霞组海相碳酸盐岩地层中发现了一套陆源碎屑岩沉积。本文通过野外剖面观察、沉积学、岩石学和锆石U-Pb年代学的方法,分析了碎屑岩的物源和沉积环境,并在此基础上恢复了研究区早二叠世的古地理格局。结果表明,栖霞组陆源碎屑岩具有典型的滨岸—潮坪相沉积特征,指示研究区在栖霞早期经历过短暂的海平面下降和暴露。碎屑锆石形貌特征指示其经历过长距离搬运或再旋回沉积,锆石U-Pb年龄主要集中在2600~2400 Ma、1800~1200 Ma、1000~700 Ma和500~400 Ma四个区间。通过与扬子地块内部及周缘二叠系、泥盆系、志留系及前寒武系地层及侵入岩体的锆石U-Pb年龄频谱进行对比,综合区域构造—沉积演化,认为志留系—泥盆系是二叠系碎屑岩可能的物源。栖霞组碎屑岩的锆石年龄频谱与梁山组极为相似,说明梁山组很可能是碎屑岩的直接物质来源。碎屑岩的出现指示当时在上扬子北缘局部地区短暂存在过海岛或古陆,为碎屑岩的形成提供有利的沉积环境和物源供给。基于碎屑岩的沉积特征和物源分析,建立了四川盆地北部早二叠世多阶段古地理演化模式。栖霞组陆源碎屑岩的发现对于深刻认识上扬子北部地区早二叠世古地理格局、构造—沉积演化以及该地区的油气勘探均有着重要的指示意义。

    Abstract:

    Terrigenous siliciclastic deposits have been found in the Lower Permian Qixia Formation marine carbonate strata at the Shuanghui section, Wangcang County, northern Sichuan Basin. The provenance and depositional environment of the terrigenous siliciclastic rocks are analyzed through field section observation, sedimentology, petrology and zircon U-Pb chronology methods. On this basis, the paleogeographic pattern of the study area are reconstructed. The results show that the siliciclastic rocks has typical coastal-tidal flat depositional characteristics, which reflects that the study area experienced a transient sea level drop and exposure in the Early Qixia Stage. The morphologies of detrital zircons in sandstone indicate that they have experienced long distance transport or recycle deposition, and the U-Pb ages of zircons are mainly concentrated in the four age ranges of 2600–2400 Ma, 1800–1200 Ma, 1000–700 Ma and 500?400 Ma. Compared with the Zircon U-Pb age spectrums of the Permian, Devonian, Silurian and Precambrian strata and intrusive rocks around the Yangtze block, and integrated regional tectono-sedimentary evolution, we propose that the Siluran-Devonian strata is the possible source of the Permian siliciclastic rocks. The zircon age frequency spectrum of the Qixia Formation siliciclastic rocks is very similar to those of Liangshan Formation, which indicates that the Liangshan Formation is probably the direct material source of the siliciclastic rocks. The occurrence of siliciclastic rocks indicates that there existed short-lived island or old land in the local area of the northern Upper Yangtze, which provided a favorable depositional environment and source supply for the formation of siliciclastic rocks. Based on the sedimentary characteristics and provenance analysis of the siliciclastic rocks, a multi-stage Early Permian paleogeographic evolution model in the northern Sichuan Basin is established. The discovery of the terrigenous siliciclastic rocks of the Qixia Formation is of great significance for the deep understanding of the Early Permian paleogeographic pattern, tectono-sedimentary evolution and hydrocarbon exploration in the northern Upper Yangtze region.

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  • 收稿日期:2023-11-14
  • 最后修改日期:2024-01-06
  • 录用日期:2024-02-04
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