Abstract This is a quantitative and qualitative study for the first time linking surface with subsurface geology to understand the occurrence and origin of enigmatic sand injectite outcrops in two sites within the Bahrah coastal plain area, northern Kuwait Bay. Field work observations and aerial photography were used to describe and characterize the surface geology and stratigraphy of the study area. Thirty-one rock samples were obtained for petrographical, fluid inclusions and strontium isotopes analyses. 3D seismic data were also used to assess the subsurface geology of the area. The petrography and microthermometry of fluid inclusions were used to understand the origin of fluids and gases associated with the formation of these sand injectites. We found that these surface geological features represent surface manifestation of subsurface geological and biological activities/processes. Therefore, we proposed a near-surface complex focused fluid injection mechanism/model responsible for the formation of the sand pipes. The model consists of five episodes: Episode-1 represents the development of near-surface geobody (? Paleoshoreline) sealed by a shale layer; Episode-2 represents the entrapment of hydrocarbons that migrated laterally up-dip within geobody, interacting with mixed seawater intrusion and fresh groundwater; Episode-3 represents the effect of biodegradation biological processes of the entrapped hydrocarbons generating CH4, CO2 and H2S gases; Episode-4 represents overpressure build-up due to gas generation exceeding pore volume of geobody and forming non-tectonic forced-folds and polygonal to semi-circular joints/fractures network; and Episode-5 represents overpressure release triggered by external factor(s) (seismic activities?) facilitating gases, water and sand remobilisation through weakened zones of natural fractures.

中文翻译：

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科威特湾北部 Bahrah 地区与非构造强迫褶皱构造相关的神秘注砂岩露头的成因

摘要 这是首次将地表与地下地质联系起来的定量和定性研究，以了解科威特湾北部 Bahrah 沿海平原地区两个地点的神秘注砂岩露头的发生和起源。实地工作观察和航空摄影被用来描述和表征研究区的地表地质和地层。获得了 31 个岩石样品，用于岩相学、流体包裹体和锶同位素分析。3D 地震数据也用于评估该地区的地下地质。流体包裹体的岩相学和显微测温被用来了解与这些砂岩注入体的形成相关的流体和气体的来源。我们发现这些地表地质特征代表了地下地质和生物活动/过程的地表表现。因此，我们提出了一种近地表复杂的聚焦流体注入机制/模型，负责沙管的形成。该模型由五集组成：第一集代表由页岩层封闭的近地表地质体（?古海岸线）的发展；第 2 集代表了在地质体内横向上倾迁移的碳氢化合物的截留，与混合的海水入侵和淡水相互作用；第 3 集表示捕获的碳氢化合物的生物降解生物过程的影响，生成 CH4、CO2 和 H2S 气体；第4集表示由于产气量超过地质体孔隙体积并形成非构造强制褶皱和多边形至半圆形节理/裂缝网络而导致的超压积聚；第 5 集表示由外部因素（地震活动？）触发的超压释放，通过天然裂缝的弱化区促进气体、水和沙子的再流动。