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Offshore site investigation
Published in White David, Cassidy Mark, Offshore Geotechnical Engineering, 2017
Bedforms such as sand mega-ripples and sand waves (e.g. Figure 2.12) are manifestations of prevailing currents and provide an excellent indication of conditions in a particular environment. Small pockmarks can also be observed and are often an indication of surface collapse due to escaping gas. Occasionally individual pockmarks can become major features, such as the one discussed by Cauquil et al. (2003) and attributed to lateral fluid migration along a particular subseabed interface, which was some 650 m in diameter and over 60 m deep (see Figure 3.10 and Figure 3.11, from data obtained using an AUV).
Seafloor pockmarks on the South Westland margin of the South Island/Te Waipounamu, Aotearoa New Zealand
Published in New Zealand Journal of Geology and Geophysics, 2023
Katherine L. Maier, Alan R. Orpin, Helen Neil
Shallow, crater-like discrete depressions on the seafloor, often referred to as pockmarks, are common morphologies along continental margins globally. Pockmarks have generated considerable interest and debate, owing to a variety of formative mechanisms (e.g. Hovland and Judd 1988; Hovland et al. 2002; Gay et al. 2006a, 2006b; Hillman et al. 2018; Stott et al. 2019). Recognition of pockmarks has increased with recent technological advances in acoustic imaging and expansion of seafloor mapping. Pockmarks occur in fine-grained surficial sediments at water depths ranging from a few to thousands of metres, spanning depositional environments from estuaries to deep-sea basins (e.g. Hovland et al. 2002 and references therein). Seafloor pockmarks can occur as isolated depressions, aligned in bands or trains, or as spatially extensive fields. They are often circular in plan-view, and ranging in size from tens of metres to kilometres in diameter (e.g. Hovland et al. 2002; Paull et al. 2002; Jobe et al. 2011; Maier et al. 2011).
Physical experimental study on the formation mechanism of pockmark by aeration
Published in Marine Georesources & Geotechnology, 2020
Xin Yan, Hongyue Sun, Zhongxuan Chen, Feixiang Shuai, Zhenlei Wei, Yiqing Xu
The formation reasons of seabed pockmarks are many and varied. It is generally believed that the formation of pockmarks is mainly due to the submarine fluid (including hydrocarbon gas, cold spring and hydrotherm, groundwater, etc.) permeating to the seabed slowly or spraying strongly through the transport channel (such as faults, weak intercalated layers and unconformity surface), and then different size of pockmarks form with the erosion of loose sediments in the seabed (Judd and Hovland 2007). Kelly et al. believed that there were two typical patterns for the formation of pockmarks: (1) Equilibrium pattern: pockmarks were caused by the slow seepage of submarine fluid over a long period of time; (2) Intensified pattern: due to the decrease of the sealing pressure of the overburden on the reservoir area caused by earthquake, storm and human engineering, the submarine fluid suddenly experienced strong seepage and even spray violently, and then pockmarks formed (Kelly et al. 1994).
Formation mechanism of large pockmarks in the subaqueous Yellow River Delta
Published in Marine Georesources & Geotechnology, 2019
Zhuangcai Tian, Xiujun Guo, Luzheng Qiao, Le Yu, Guohui Xu, Tao Liu
Pockmarks are a common type of submarine depression and are usually associated with geological structures, such as fractures, diapirs, and faults. These features are generally thought to form via the eruption of fluid through the seabed, which implies the existence of escaping submarine methane (Naudts et al. 2008; Li et al. 2013; Liu et al. 2013; Sultan et al. 2014).