Citation: | YANG Zhipeng, LI Lei, ZHANG Wei, GONG Guangchuan, DANG Xingyu, CHENG Linyan, GAO Yifan. Characteristics and genesis of submarine pockmarks -- A case from the Niger Delta[J]. Marine Geology & Quaternary Geology, 2020, 40(6): 61-70. doi: 10.16562/j.cnki.0256-1492.2019111902 |
Based on the high-resolution three-dimensional seismic data of about 1300 km2 acquired from the Niger Delta Basin of the Gulf of Guinea in West Africa, studied in this paper are the temporal and spatial distribution patterns of pockmarks, the relationship between pockmarks and sea bottom channels, and the genesis of various types of pockmarks. Through the fine interpretation of the target horizon and the extraction of various seismic attributes, there have found 75 pockmarks in the northwest of the study area, 56 pockmarks found above channels, and 62 pockmarks distributed in other parts of the study area. There are three types of pockmarks, such as pockmarks in belts, complex pockmarks and isolated pockmarks. The causes and distribution patterns of pockmarks are affected by the erosion and cutting of buried channel sections. The corresponding turbidity channels in the stratum below the pockmarks produce fluids. The upward migration of fluids causes the stratum to be discontinuous, which in turn affects the stratum and distribution of pockmarks. According to the stratigraphic characteristics and filling mode, the genesis of pockmarks is classified into ancient channel genesis and fault genesis.
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Location map and stratigraphic chronology of the Niger delta study area (revised from reference[35])
Pockmark distribution map in the study area (D1 and D2 show the profiles of channels and pockmarks)
Profiles of seabed pockmark
Distribution profile showing pockmark and channel (See Fig.2a for location)
Sediment fillings in channels below pockmarks
Geometrical characteristics and subseafloor structures for the five types of pockmarks (revised from reference[43])
Schematic diagram of a buried ancient channel (See Fig.2c for location)
Schematic diagram of gas chimney below pockmark
Occurance of faults under of pockmarks (see Fig.2b for location. Red lines represent faults)
The formation mechanisms of isolated pockmarks (revised from reference[43])