The Absolute Age and Origin of the Giant Gypsum Geode of Pulpí (Almería, SE Spain)

Subaqueous gypsum (CaSO4·2H2O) crystals are relatively common in epithermal systems where sulfide ore deposits present. The Giant Geode of Pulpí (Almería, SE Spain) hosts some the largest (up to 2 m length) subaqueous discovered date. Here, we present first U-series ages its and reconstruct oxygen hydrogen isotopic composition (δ18O δ2H) paleo-aquifer from which formed by using stable isotopes hydration water. We successfully dated onset precipitation at 164 ± 15 ka. However, extremely low U concentration (11 ppb) high detrital Th content (230Th/232Th 3.2) hinder accurate dating other samples. δ18O δD values during growth aligned with local meteoric water line, suggesting that sulfate-enriched mother solution consisted recharged aquifer period. mean = −6.5 0.1‰ δ2H −42.3 0.5‰) formation was similar current groundwater this area −6.1 0.8‰, −42 6‰). differences observed samples collected distinct locations individual were probably related changes aquifer, as a consequence varying climate impacted on rainwater thousands years region. Our results indicated selenite may be useful for paleo-hydrological reconstructions. improving analytical techniques concentrations will essential obtain reliable records Quaternary cave future.