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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.

 

To monitor meteorologic conditions on San Salvador Island throughout the duration of our well and lake instrumentation campaigns (see associated datasets), we installed an automatic weather station (AWS) at the Gerace Research Centre (GRC) located on the island's northern shore. The GRC weather station was equipped with a HOBO U30 Data Logger that recorded sensor measurements at a 15-minute sampling rate from November 2017 through October 2019. The AWS measured air temperature, and relative humidity with a Temperature/RH Smart Sensor (S-WSB-M003) installed within a solar radiation shield to prevent overheating. Rainfall was measured with a HOBO/Onset Rain Gauge Smart Sensor that using a tipping bucket mechanism mounted on a stainless steel shaft with brass bearings within aluminum housing to monitor rainfall rates up to 12.7 cm per hour. Atmospheric pressure was measured using a Barometric Pressure Smart Sensor within weatherproof housing with an accuracy of +/- 3.0 mbar, a resolution of 1.0 mbar, and a measurement range of 660-1070 mbar. Incoming shortwave solar radiation was measured with a silicon pyranometer (Solar Radiation Smart Sensor) mounted onto the weather station using the Onset Light Sensor Bracket. Data gaps due to sensor failure or proceeding sensor addition to the weather station producing null values are filled with "NaN" (i.e., not a number). 

San Salvador Island is located on an isolated carbonate platform situated on the southeastern edge of the Bahamian Archipelago. Over half of the island's small area is covered by hypersaline lakes that expose the island's water table to evaporation. Many of the island's lakes are connected to the ocean by karst conduits, thereby allowing tidal pumping to drive the exchange of fresh and saltwater during tidal cycles. To investigate the influence of tidal cycles on lake water levels, we monitored water temperature, pressure, and specific conductivity for several lakes located on San Salvador Island, Bahamas. We instrumented lakes with HOBO Onset U20L-04 loggers with a water level accuracy of 0.14 cm. HOBO Onset data loggers were set to record measurements at intervals ranging from 30 seconds to 15 minutes. We chose sampling intervals as to not exceed the HOBO logger's data recording capacity based on our estimated return to the site to download data. For most of the lakes instrumented in this study, we combine multiple timeseries into an individual location file. Accordingly, a single data table may have temporal data gaps and time periods with different sampling intervals. The README.md file included with this dataset contains a table with lake names and locations, sampling rates, and deployment dates. 

San Salvador Island is a small isolated carbonate platform on the southeastern edge of the Bahamian Archipelago. The Line Hole well field is located on an eogenetic karst aquifer on San Salvador Island's northern coast. The island's negative water budget and extensive lake cover have resulted in the upconing of saline water that has fragmented the once continuous freshwater lens. The Line Hole well field consists of several 15-cm diameter wells drilled into the fresh-water lens and arranged in a line perpendicular to the shore. The well field also has two monitoring wells (LH 1, and LH 13), that penetrate approximately 7 m below the water table into higher salinity groundwater. The well field was abandoned in 2016 upon saltwater intrusion to the aquifer. To evaluate the connectivity between the eogenetic karst aquifer monitored by the Line Hole well field and the ocean, we instrumented wells with HOBO U20L-04 loggers to measure pressure and temperature timeseries. We instrumented wells LH4, and LH8, in addition to the monitoring wells LH1 and LH13.