17Oexcess in Devils Hole calcite: an indicator of equilibrium fractionation and paleo moisture sources

• 17 O excess in Devils Hole calcite is indistinguishable between glacials and interglacials. • The fractionation slope in this very slow growing calcite is consistent with that of fast-growing carbonates. • Paleo-water 17 O excess suggests continental recycling of moisture during interglacials. • Moisture recycling during glacials is significantly reduced. Paleo-hydrology is typically based on measurements of δ 18 O in carbonate archives of environments on land. Triple oxygen isotopes (given as 17 O excess = 10 6 [ln (10 –3 δ 17 O + 1) – 0.528 ln (10 –3 δ 18 O + 1)] in CaCO 3 has been recently shown to record 17 O excess of the carbonate parent water, thus providing additional paleo-hydrology information. Paleo rain-water 17 O excess , as recorded in speleothems, may be indicative of changes in moisture source location and evaporative conditions. The link between water and carbonate 17 O excess , as characterized by the fractionation slope θ (= ln 17 α / ln 18 α), has been determined in fast growing synthetic and biogenic carbonates, and in a few vadose speleothems. Here, we use the very slow growing mammillary calcite of Devils Hole to examine the fractionation slope at equilibrium, and to assess hypotheses of pluvial glacial periods in the Great Basin (USA). Results suggests that the equilibrium fractionation slope is consistent with that of fast-growing carbonates. 17 O excess values in Devils Hole paleo water are indistinguishable between glacial and interglacial extremes, as well as through Terminations II and IV. These reconstructed 17 O excess values are also similar to that of modern Devils Hole water (45 per meg). We interpret the observed 17 O excess to reflect significant continental recycling of the moisture reaching the inland site of Devils Hole during interglacials, but much reduced recycling during glacials.