Offshore Freshened Groundwater in Continental Margins
Offshore Freshened Groundwater in Continental Margins
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DOI：
10.1029/2020rg000706
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发表时间：
2020-11
影响因子：
25.2
通讯作者：
A. Micallef;M. Person;C. Berndt;C. Bertoni;D. Cohen;B. Dugan;R. Evans;A. Haroon;C. Hensen;M. Jegen;K. Key;H. Kooi;V. Liebetrau;J. Lofi;B. Mailloux;Renée Martin‐Nagle;H. Michael;T. Mueller;M. Schmidt;K. Schwalenberg;E. Trembath-Reichert;B. Weymer;Yipeng Zhang;A. Thomas
中科院分区：
文献类型：
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作者：
A. Micallef;M. Person;C. Berndt;C. Bertoni;D. Cohen;B. Dugan;R. Evans;A. Haroon;C. Hensen;M. Jegen;K. Key;H. Kooi;V. Liebetrau;J. Lofi;B. Mailloux;Renée Martin‐Nagle;H. Michael;T. Mueller;M. Schmidt;K. Schwalenberg;E. Trembath-Reichert;B. Weymer;Yipeng Zhang;A. Thomas
最早于20世纪60年代报道的近海淡水地下水(OFG)现已在世界大部分大陆边缘被记录在案。在这篇综述中，我们编制了一个记录OFG发生的数据库，并对其进行分析，以确定OFG的一般特征和控制因素。我们还评估了用于绘制和描述OFG的方法，确定了主要的知识差距，并提出了解决这些差距的战略。OFG的全球体积为1×106千米~3；主要分布在距海岸55公里范围内，水深达100米。OFG主要赋存于被动边缘的硅质碎屑含水层中，并在更新世海平面低水位时由大气水补充。影响OFG分布的关键因素是地形驱动的水流、盐碱对流的盐化、渗透率对比以及渗透层和封闭层的连续性/连通性。钻孔孔隙水的地球化学和稳定同位素测量提供了对OFG侵位机制的洞察，而地震反射剖面、电磁测量和数值模型的最新进展提高了我们对OFG几何形状和控制的理解。可以通过应用同位素年龄示踪剂、联合反演电磁和地震反射数据以及开发三维水文模型来解决诸如OFG的范围和功能及其布设时间等关键知识空白。我们表明，这些进展与特定地点的模拟相结合，对于评估OFG作为非常规水源的潜在用途及其在海底下地质微生物学中的作用是必要的。
First reported in the 1960s, offshore freshened groundwater (OFG) has now been documented in most continental margins around the world. In this review we compile a database documenting OFG occurrences and analyze it to establish the general characteristics and controlling factors. We also assess methods used to map and characterize OFG, identify major knowledge gaps, and propose strategies to address them. OFG has a global volume of 1 × 106 km3; it predominantly occurs within 55 km of the coast and down to a water depth of 100 m. OFG is mainly hosted within siliciclastic aquifers on passive margins and recharged by meteoric water during Pleistocene sea level lowstands. Key factors influencing OFG distribution are topography‐driven flow, salinization via haline convection, permeability contrasts, and the continuity/connectivity of permeable and confining strata. Geochemical and stable isotope measurements of pore waters from boreholes have provided insights into OFG emplacement mechanisms, while recent advances in seismic reflection profiling, electromagnetic surveying, and numerical models have improved our understanding of OFG geometry and controls. Key knowledge gaps, such as the extent and function of OFG, and the timing of their emplacement, can be addressed by the application of isotopic age tracers, joint inversion of electromagnetic and seismic reflection data, and development of three‐dimensional hydrological models. We show that such advances, combined with site‐specific modeling, are necessary to assess the potential use of OFG as an unconventional source of water and its role in sub‐seafloor geomicrobiology.