Can Offshore Meteoric Groundwater Generate Mechanical Instabilities in Passive Continental Margins?
Can Offshore Meteoric Groundwater Generate Mechanical Instabilities in Passive Continental Margins?
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DOI：
10.1029/2022jf006954
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发表时间：
2023-02
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影响因子：
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通讯作者：
A. Micallef;M. Person;Shubhangi Gupta;N. Saadatkhah;A. Camille;Ò. Gratacós
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文献类型：
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作者：
A. Micallef;M. Person;Shubhangi Gupta;N. Saadatkhah;A. Camille;Ò. Gratacós
近海大气地下水（OMG）长期以来一直被认为是全球大陆边缘海底地貌过程的驱动力。由于我们对OMG流动和渗流的分布和速率及其作为侵蚀/不稳定剂的功效的了解有限，因此测试这一假设具有挑战性。在这里，我们进行了数值模拟的地下水流和斜坡稳定性的概念模型和不断发展的地层被动硅质岩和碳酸盐边缘的情况下，以评估是否OMG及其演变在第四纪晚期冰川周期可以产生孔隙压力触发机械不稳定性海底。概念模型结果表明，使用OMG流的机械不稳定性最有可能发生在外陆架到上斜坡，在末次冰期最大海平面低水位或之前不久。不断变化的地层模型表明，OMG流动是碳酸盐岩边缘情况下孔隙压力发展和不稳定的关键驱动因素。在硅质岩边缘的情况下，OMG流起着次要的作用，在预处理的边坡破坏。碳酸盐岩边缘的空间/地层异质性程度较高，其沉积物的剪切强度较低，以及沉积物负荷产生的超压有限，这可能解释了碳酸盐岩边缘与硅质岩边缘相比，对OMG流产生的机械不稳定性具有更高的敏感性。OMG可能在碳酸盐边缘地貌中发挥了更重要的作用（例如，巴哈马，马尔代夫）比目前认为的。
Offshore meteoric groundwater (OMG) has long been hypothesized to be a driver of seafloor geomorphic processes in continental margins worldwide. Testing this hypothesis has been challenging because of our limited understanding of the distribution and rate of OMG flow and seepage, and their efficacy as erosive/destabilizing agents. Here we carry out numerical simulations of groundwater flow and slope stability using conceptual models and evolving stratigraphy—for passive siliciclastic and carbonate margin cases—to assess whether OMG and its evolution during a late Quaternary glacial cycle can generate the pore pressures required to trigger mechanical instabilities on the seafloor. Conceptual model results show that mechanical instabilities using OMG flow are most likely to occur in the outer shelf to upper slope, at or shortly before the Last Glacial Maximum sea‐level lowstand. Models with evolving stratigraphy show that OMG flow is a key driver of pore pressure development and instability in the carbonate margin case. In the siliciclastic margin case, OMG flow plays a secondary role in preconditioning the slope to failure. The higher degree of spatial/stratigraphic heterogeneity of carbonate margins, lower shear strengths of their sediments, and limited generation of overpressures by sediment loading may explain the higher susceptibility of carbonate margins, in comparison to siliciclastic margins, to mechanical instability by OMG flow. OMG likely played a more significant role in carbonate margin geomorphology (e.g., Bahamas, Maldives) than currently thought.