Earth Science Frontiers ›› 2024, Vol. 31 ›› Issue (3): 284-297.DOI: 10.13745/j.esf.sf.2023.9.22

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Volcanic sedimentation of Cretaceous Jiufotang Formation in the Chaoyang Basin and its impact on organic matter enrichment

ZHANG Jiazhi1(), JIANG Zaixing1,*(), XU Jie2, WEI Siyuan1, SONG Lizhou3, LIU Tong1, SHEN Zhihan1, JIANG Xiaolong4, LI Yongfei5,6, ZHANG Xi7   

  1. 1. School of Energy Resources, China University of Geosciences(Beijing), Beijing 100083, China
    2. School of Ocean Sciences, China University of Geosciences(Beijing), Beijing 100083, China
    3. Daqing Oilfield Production Technology Institute, Daqing 163000, China
    4. Beijing Yalong Technology Development Co., Ltd., Beijing 100096, China
    5. Shenyang Geological Survey Center, China Geological Survey, Shenyang 110034, China
    6. MNR Observation and Research Station of Mesozoic Stratigraphic System in Western Liaoning, Shenyang 110034, China
    7. Exploration and Development Research Institute,Northeast Oil & Gas Branch,SINOPEC,Changchun 130062, China
  • Received:2023-02-16 Revised:2023-09-11 Online:2024-05-25 Published:2024-05-25

Abstract:

The Chaoyang Basin in western Liaoning, situated in the eastern section of the Yanshan tectonic belt, is a fault basin from the Mesozoic era on the periphery of Songliao. The level of exploration understanding in this region is relatively low. Previous studies on the Lower Cretaceous Jiufotang Formation in the Chaoyang Basin primarily focused on lacustrine deposits, overlooking the significant impact of volcanic events on the basin’s sedimentation. To address this gap, regional geological data investigation, drilling core description, core thin section data observation, and test data analysis were conducted. By classifying pyroclastic rocks into sedimentary pyroclastic rocks and pyroclastic sedimentary rocks based on their content and subdividing them into 11 lithofacies types and 9 lithofacies combinations according to particle size, composition, and sedimentary structure characteristics, five causal mechanisms were proposed: pyroclastic flow, volcanic hyperpycnal flow, volcanic ash heterogeneous light flow, hydrothermal intrusion, and microbial induction. The establishment of the volcanic-lake sedimentary model of the Jiufotang Formation in the Chaoyang Basin, based on volcanic sedimentary sequences and core observation findings, offers a theoretical foundation for oil and gas resource exploration and development in the area. Research indicates that volcanic material positively influences organic matter enrichment in the lake basin. Geochemical tests on source rocks of the Jiufotang Formation in the Chaoyang Basin revealed that samples containing volcanic fine particles involved in sedimentation exhibited better organic matter abundance and enrichment. Given the similar volcanic activity geological background in other basins within the Yanshan tectonic belt, these findings also serve as valuable comparative references for sedimentology and oil and gas resource research in those regions.

Key words: Chaoyang Basin, Jiufotang Formation, lithofacies type and combination, genesis mechanism, organic matter enrichment

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