First identification and its geological significance of seafloor pockmarks sediments in the Upper Ordovician Wufeng Formation in China
SHI Zhiqiang1,2, PENG Shenyuan1, ZHAO Ziteng1
1 Institute of Sedimentary Geology,Chengdu University of Technology,Chengdu 610059,China; 2 State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Chengdu University of Technology,Chengdu 610059,China
Abstract Seafloor pockmarks are commonly seen in various marine environments. The study on the pockmark sediments,however,have been hardly involved in the literature,causing few knowledges of their characteristics,origin and identification. In this study,we recognized the pockmark sediments from the Paleozoic fine-grained rocks for the first time in China. Based on the field observations and sampling of Upper Ordovician Wufeng Formation at Ganziping and Xiebutou in Shizhu,Chongqing,we tested pockmark rocks with microscope,scanning electron microscope(SEM),and major and trace element analyses. We found the bed chaos and arched beds in the lentoid or cuneal pockmark sediment body. Breccia carved by siliceous veins,are commonly seen,together with asphalt and barite,hematite minerals in the pockmark sediments. Observations and results of major element and REE suggest that the formation of pockmarks were unrelated with hydrothermal liquid and cold seeps. All the geological facts indicate the low-matured oil and gas generated from the Wufeng Formation as the first essential for the formation of pockmarks. The identification marks of deep-time pockmarks are thought as: (i)negative relief in seismic sections,(ii)lentoid or cuneal sediment body,(iii)chaos beds,(iv)arched beds,and(v)hiatus and temporal chaos of sediments. Meanwhile,petrological,stratigraphical,paleoenvironmental and petrogeological significances of the pockmarks in the Wufeng Formation are discussed in this study.
Fund:Co-funded by Science and Tectnology Planning Project,Sichuan Province(No.2021YJ0353)and National Natural Science Foundation of China(No.41272131)
About author: SHI Zhiqiang,born in 1972,professor,is mainly engaged in research on sedimentology. E-mail: szqcdut@163.com.
Cite this article:
SHI Zhiqiang,PENG Shenyuan,ZHAO Ziteng. First identification and its geological significance of seafloor pockmarks sediments in the Upper Ordovician Wufeng Formation in China[J]. JOPC, 2024, 26(2): 255-268.
SHI Zhiqiang,PENG Shenyuan,ZHAO Ziteng. First identification and its geological significance of seafloor pockmarks sediments in the Upper Ordovician Wufeng Formation in China[J]. JOPC, 2024, 26(2): 255-268.
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