Multiple drivers and controls of pockmark formation across the Canterbury Margin, New Zealand
Multiple drivers and controls of pockmark formation across the Canterbury Margin, New Zealand
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DOI：
10.1111/bre.12663
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发表时间：
2022-03
期刊：
影响因子：
3.2
通讯作者：
A. Micallef;T. Averes;J. Hoffmann;G. Crutchley;J. Mountjoy;M. Person;D. Cohen;S. Woelz;S. Bury;C. V. Ahaneku;Daniele Spatola;N. Luebben;S. Miserocchi;S. Krastel;Martina Torelli;K. Omosanya
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文献类型：
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作者：
A. Micallef;T. Averes;J. Hoffmann;G. Crutchley;J. Mountjoy;M. Person;D. Cohen;S. Woelz;S. Bury;C. V. Ahaneku;Daniele Spatola;N. Luebben;S. Miserocchi;S. Krastel;Martina Torelli;K. Omosanya
在所有大陆边都有记录表明，由于集中的流体渗漏而形成的浅海底凹陷，称为麻坑。在这项研究中，我们展示了如何麻点的形成可以是多种因素的组合的结果-流体类型，超压，海底沉积物类型，地层和底流。我们将多波束回声测深仪和地震反射数据，沉积物岩心和孔隙水样品，地下水和天然气水合物的数值模型，从坎特伯雷边缘（新西兰）。在中、外陆架和下大陆坡，发现了6800多个表面麻坑，密度达到每平方公里100个，还有数量不明的埋藏麻坑。横跨大陆架和斜坡的流体管道包括浅到深的烟囱/管道。甲烷与生物和/或热成因的起源是主要的流体形成的流动和逃逸功能，虽然盐水和淡水地下水也可能渗透到整个斜坡。流体流动和渗流的主要驱动力是沉积物加载产生的跨斜坡超压和外大陆架超压层段上方的薄沉积物覆盖层。其他过程（例如甲烷的生成和流动、海平面下降导致的静水压力降低）也可能是流体流动和渗流特征的原因，特别是在大陆架上。麻点的出现与海底的泥质沉积物相吻合，而它们的平面形状被底流拉长。
Shallow seabed depressions attributed to focused fluid seepage, known as pockmarks, have been documented in all continental margins. In this study, we demonstrate how pockmark formation can be the result of a combination of multiple factors—fluid type, overpressures, seafloor sediment type, stratigraphy and bottom currents. We integrate multibeam echosounder and seismic reflection data, sediment cores and pore water samples, with numerical models of groundwater and gas hydrates, from the Canterbury Margin (off New Zealand). More than 6800 surface pockmarks, reaching densities of 100 per km2, and an undefined number of buried pockmarks, are identified in the middle to outer shelf and lower continental slope. Fluid conduits across the shelf and slope include shallow to deep chimneys/pipes. Methane with a biogenic and/or thermogenic origin is the main fluid forming flow and escape features, although saline and freshened groundwaters may also be seeping across the slope. The main drivers of fluid flow and seepage are overpressure across the slope generated by sediment loading and thin sediment overburden above the overpressured interval in the outer shelf. Other processes (e.g. methane generation and flow, a reduction in hydrostatic pressure due to sea‐level lowering) may also account for fluid flow and seepage features, particularly across the shelf. Pockmark occurrence coincides with muddy sediments at the seafloor, whereas their planform is elongated by bottom currents.