Calcium carbonate precipitation in the Cueva di Watapana on Bonaire, Netherlands Antilles

Calcium carbonate precipitates as low Mg-calcite and aragonite in slightly brackish water in a cave in the Pleistocene Middle Terrace of southern Bonaire. The calcium carbonate precipitates at the atmosphere-water interface forming floating calcite scales (calcite ice). Aragonite crystals frequently link the calcite scales together. The juxtaposition of calcite and aragonite is explained by calcite precipitation at the water-surface in nearly fresh water, with low Mg/Ca ratio, followed by the formation of aragonite near the bottom of the pool in more saline water with higher Mg/Ca ratio. The saline water with a higher magnesium content is most likely Caribbean sea water working its way inland through underground fissures.