Flank margin caves are extreme endmembers of vuggy porosity that form as diagenesis drives the progressive coalescence of smaller solutional pore spaces. Due to their morphological isolation during formation, the prevailing hypothesis has been that fluid flow in and out of flank margin caves occurs via the matrix permeability and that adjacent chambers only become hydraulically connected through nonmatrix porosity during burial, collapse, and fracturing. To our knowledge, however, no studies have evaluated how flank margin caves are connected to regional flow systems in modern carbonate platforms. In this study, we evaluate the connectivity of wells, boreholes, blue holes, and flank margin caves in increasingly older bedrock on San Salvador Island, Bahamas, using tidal attenuation analysis. Phreatic karst features are not reported in Holocene bedrock, and permeability magnitudes from wells suggest Holocene deposits connect to the ocean along matrix-dominated flow paths. Permeability magnitudes in bedrock surrounding wells, boreholes, and karst features deposited during Marine Isotope Substage (MIS) 5e suggest connection to the ocean through matrix and touching vug porosity. Boreholes, blue holes, and flank margin caves in pre-MIS5 bedrock connect to the ocean via touching vugs. We suggest that increasing bedrock permeability, cave number, and cave size observed within progressively older bedrock on San Salvador is a function of the cumulative number of freshwater lenses emplaced over successive sea-level stillstands. We suggest that the morphologies of the two largest caves are consistent with dissolution in multiple lenses occupying lower elevations, collapse resulting in breakout domes, and overprinting of collapse chambers during subsequent highstands. As a result, some caves may not reflect connectivity of the bedrock surrounding the main chambers but may reflect connectivity of more diagenetically mature bedrock at lower elevations where their antecedent chambers formed.

中文翻译：

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侧缘洞穴在埋藏前可以连接到区域广泛的接触孔洞网络：对洞穴形成和流体流动的影响

侧缘洞穴是孔洞孔隙度的极端端元，随着成岩作用驱动较小的溶解孔隙空间的逐渐合并而形成。由于它们在形成过程中的形态隔离，普遍的假设是流体流入和流出侧缘洞穴是通过基质渗透率发生的，并且相邻的腔室仅在埋藏、坍塌和压裂期间通过非基质孔隙度成为水力连接。然而，据我们所知，没有研究评估侧缘洞穴如何与现代碳酸盐平台中的区域流动系统相连。在这项研究中，我们使用潮汐衰减分析评估了巴哈马圣萨尔瓦多岛日益古老的基岩中井、钻孔、蓝洞和侧缘洞穴的连通性。在全新世基岩中没有报道潜水岩溶特征，井的渗透率大小表明全新世沉积物沿着基质主导的流动路径连接到海洋。在海洋同位素亚级 (MIS) 5e 期间沉积的井、钻孔和岩溶特征周围基岩的渗透率大小表明通过基质和接触孔洞孔隙度与海洋相连。MIS5 之前基岩中的钻孔、蓝洞和侧缘洞穴通过接触孔洞与海洋相连。我们认为，在圣萨尔瓦多逐渐古老的基岩中观察到的基岩渗透性、洞穴数量和洞穴大小的增加是连续海平面静止支架上淡水透镜体累积数量的函数。我们认为，两个最大洞穴的形态与占据较低海拔的多个透镜中的溶解、坍塌导致突破穹顶以及随后高位期间坍塌室的叠印一致。因此，一些洞穴可能无法反映主室周围基岩的连通性，但可能反映了在较低海拔的成岩成熟基岩的连通性，在那里形成了它们的先行室。