Formation mechanism of deep-sea giant pockmarks: A case study of the Reed Basin in the South China Sea
Formation mechanism of deep-sea giant pockmarks: A case study of the Reed Basin in the South China Sea
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DOI：
10.1016/j.geomorph.2023.108726
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发表时间：
2023-05
期刊：
影响因子：
3.9
通讯作者：
Ziyin Wu;Dineng Zhao;Jieqiong Zhou;Zhihao Liu;Mingwei Wang;J. Shang;Xiaowen Luo;Xiaoming Qin
中科院分区：
文献类型：
--
作者：
Ziyin Wu;Dineng Zhao;Jieqiong Zhou;Zhihao Liu;Mingwei Wang;J. Shang;Xiaowen Luo;Xiaoming Qin
麻坑在世界海底分布广泛，但直径大于1 km的巨型麻坑并不多见，其形成机制至今仍是个谜。利用高分辨率多波束测深资料，首次在中国南海里德海盆识别出巨型麻坑。这些形状各异的巨型麻点成群出现，主要沿着海底峡谷的两侧。我们提出了一个关于深海麻坑形成机制的新假说，即里德盆地的麻坑是由海底天然气爆炸形成的，广泛发育的碳酸盐岩储存了沿沿着NE-SW向断裂不断渗漏的埋藏气，盖层被海底峡谷下切形成力学薄弱线，在海平面快速下降期间，降压导致埋藏气沿这些线沿着迅速喷出，形成巨大的麻点群。分析了全球21个地区报告的海底麻点，发现麻点深径比（d/r）的平均中值接近0.3。根据弹坑形成理论，发现该弹坑的D/R比也接近0.3，这为深海麻坑的形成机制提供了新的思路。研究还发现，麻点的平均大小受水深的控制，在深海中更容易形成巨型麻点。由于这些结果将容易观察到的水深特征与埋藏天然气矿床的存在相关联，因此它们对深海天然气资源的勘探和研究具有重要意义。
Pockmarks are widely distributed in the seabed around the world, however, mega pockmarks with diameters >1 km are rare, and their formation mechanisms remain enigmatic. Using high-resolution multi-beam bathymetric data, we firstly identified mega pockmarks in the Reed Basin in the South China Sea (SCS). These mega pockmarks of various shapes occur in groups, primarily along the sides of submarine canyons. We propose a new hypothesis about the formation mechanism of the deep-sea pockmarks that pockmarks in the Reed Basin are formed by seafloor gas explosions, widely developed carbonates store buried gas that continuously seeps along NE-SW trending faults, cap layers are undercut by submarine canyons forming lines of mechanical weakness, during periods of rapid sea level fall, depressurization causes buried gas to be rapidly ejected along these lines, forming mega pockmark groups. Submarine pockmarks reported in 21 regions globally have been analyzed, and it is found that the average median of the ratio of depth to radius (d/r) of the pockmarks is close to 0.3. Based on the theory of crater formation, it is found that the d/r ratio of the crater is also close to 0.3, which provides a new idea for the formation mechanism of deep-sea pockmarks. It is also found that the average size of the pockmarks is controlled by the water depth, and giant pockmarks are more likely to form in the deep sea. Because these results correlate easily observed bathymetric features to the presence of buried gas deposits, they have important implications for the exploration and research of deep-sea gas resources.